Class 10 CBSE Science – 500 High-Level Questions
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Question 14 Marks 1. Chemical Reactions and Equations Analyze the characteristics of a chemical reaction and explain how different observations provide evidence of chemical change. Click to View Answer ▼
Answer:
A chemical reaction is a process in which one or more substances change into new substances with different properties. Important observations include change in colour, evolution of a gas, formation of a precipitate, change in temperature, and change in state. For example, when zinc reacts with dilute hydrochloric acid, hydrogen gas is evolved: Zn + 2HCl → ZnCl₂ + H₂. When lead nitrate reacts with potassium iodide, a yellow precipitate of lead iodide forms. A temperature change is observed when quicklime reacts with water. These observations help identify that a chemical change has occurred. Thus, chemical reactions can often be recognized through observable physical or energy changes.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 24 Marks 1. Chemical Reactions and Equations Explain combination, decomposition, displacement and double displacement reactions with balanced examples. Click to View Answer ▼
Answer:
A combination reaction occurs when two or more substances form a single product. Example: CaO + H₂O → Ca(OH)₂. A decomposition reaction is the opposite, where one compound breaks into simpler substances; calcium carbonate decomposes on heating: CaCO₃ → CaO + CO₂. In a displacement reaction, a more reactive element displaces a less reactive element from its compound, such as Zn + CuSO₄ → ZnSO₄ + Cu. A double displacement reaction involves exchange of ions between two compounds. For example, Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃, where yellow PbI₂ precipitates. These reactions are classified according to how reactants rearrange to form products.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 34 Marks 1. Chemical Reactions and Equations Explain oxidation and reduction and show why they occur simultaneously in a redox reaction. Click to View Answer ▼
Answer:
Oxidation and reduction are complementary processes. Oxidation can be understood as gain of oxygen, loss of hydrogen, or loss of electrons, while reduction involves loss of oxygen, gain of hydrogen, or gain of electrons. Both processes occur simultaneously in a redox reaction. For example, in CuO + H₂ → Cu + H₂O, copper oxide loses oxygen and is reduced to copper, whereas hydrogen gains oxygen and is oxidised to water. In terms of electrons, a substance that loses electrons is oxidised and another substance gains those electrons and is reduced. Therefore, oxidation cannot normally occur independently of reduction in a redox process.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 44 Marks 1. Chemical Reactions and Equations Explain corrosion, its effects and the major methods used to prevent it. Click to View Answer ▼
Answer:
Corrosion is the gradual deterioration of a metal due to chemical or electrochemical reactions with substances in the environment. Iron reacts with oxygen and moisture to form rust. Corrosion weakens structures, damages machines and causes economic losses. It can be prevented by isolating the metal from air and moisture or by making the metal less reactive. Common methods include painting, oiling or greasing, galvanisation, electroplating and alloying. Galvanisation protects iron by coating it with zinc. Stainless steel resists corrosion because it contains elements such as chromium that form a protective surface layer. Therefore, controlling contact with oxygen and moisture is an important strategy for preventing corrosion.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 54 Marks 1. Chemical Reactions and Equations Explain rancidity and discuss practical methods for preventing it in food materials. Click to View Answer ▼
Answer:
Rancidity is the oxidation of fats and oils in food, which produces unpleasant smell and taste. It reduces food quality and may make food unsuitable for consumption. Exposure to oxygen, light, heat and moisture can accelerate the process. Rancidity can be prevented by storing food in airtight containers, refrigeration, adding suitable antioxidants and using vacuum or inert-gas packaging. For example, packets of chips are often filled with nitrogen to reduce contact between the oil and oxygen. Keeping food away from excessive heat and direct sunlight also slows oxidation. Thus, limiting oxygen and other favourable conditions helps preserve the freshness and quality of fatty foods.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 64 Marks 1. Chemical Reactions and Equations Analyze the characteristics of a chemical reaction and explain how different observations provide evidence of chemical change Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A chemical reaction is a process in which one or more substances change into new substances with different properties. Important observations include change in colour, evolution of a gas, formation of a precipitate, change in temperature, and change in state. For example, when zinc reacts with dilute hydrochloric acid, hydrogen gas is evolved: Zn + 2HCl → ZnCl₂ + H₂. When lead nitrate reacts with potassium iodide, a yellow precipitate of lead iodide forms. A temperature change is observed when quicklime reacts with water. These observations help identify that a chemical change has occurred. Thus, chemical reactions can often be recognized through observable physical or energy changes This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 74 Marks 1. Chemical Reactions and Equations Explain combination, decomposition, displacement and double displacement reactions with balanced examples Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A combination reaction occurs when two or more substances form a single product. Example: CaO + H₂O → Ca(OH)₂. A decomposition reaction is the opposite, where one compound breaks into simpler substances; calcium carbonate decomposes on heating: CaCO₃ → CaO + CO₂. In a displacement reaction, a more reactive element displaces a less reactive element from its compound, such as Zn + CuSO₄ → ZnSO₄ + Cu. A double displacement reaction involves exchange of ions between two compounds. For example, Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃, where yellow PbI₂ precipitates. These reactions are classified according to how reactants rearrange to form products A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 84 Marks 1. Chemical Reactions and Equations Explain oxidation and reduction and show why they occur simultaneously in a redox reaction Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Oxidation and reduction are complementary processes. Oxidation can be understood as gain of oxygen, loss of hydrogen, or loss of electrons, while reduction involves loss of oxygen, gain of hydrogen, or gain of electrons. Both processes occur simultaneously in a redox reaction. For example, in CuO + H₂ → Cu + H₂O, copper oxide loses oxygen and is reduced to copper, whereas hydrogen gains oxygen and is oxidised to water. In terms of electrons, a substance that loses electrons is oxidised and another substance gains those electrons and is reduced. Therefore, oxidation cannot normally occur independently of reduction in a redox process Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 94 Marks 1. Chemical Reactions and Equations Explain corrosion, its effects and the major methods used to prevent it Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Corrosion is the gradual deterioration of a metal due to chemical or electrochemical reactions with substances in the environment. Iron reacts with oxygen and moisture to form rust. Corrosion weakens structures, damages machines and causes economic losses. It can be prevented by isolating the metal from air and moisture or by making the metal less reactive. Common methods include painting, oiling or greasing, galvanisation, electroplating and alloying. Galvanisation protects iron by coating it with zinc. Stainless steel resists corrosion because it contains elements such as chromium that form a protective surface layer. Therefore, controlling contact with oxygen and moisture is an important strategy for preventing corrosion A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 104 Marks 1. Chemical Reactions and Equations Explain rancidity and discuss practical methods for preventing it in food materials Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Rancidity is the oxidation of fats and oils in food, which produces unpleasant smell and taste. It reduces food quality and may make food unsuitable for consumption. Exposure to oxygen, light, heat and moisture can accelerate the process. Rancidity can be prevented by storing food in airtight containers, refrigeration, adding suitable antioxidants and using vacuum or inert-gas packaging. For example, packets of chips are often filled with nitrogen to reduce contact between the oil and oxygen. Keeping food away from excessive heat and direct sunlight also slows oxidation. Thus, limiting oxygen and other favourable conditions helps preserve the freshness and quality of fatty foods For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 114 Marks 1. Chemical Reactions and Equations Analyze the characteristics of a chemical reaction and explain how different observations provide evidence of chemical change Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A chemical reaction is a process in which one or more substances change into new substances with different properties. Important observations include change in colour, evolution of a gas, formation of a precipitate, change in temperature, and change in state. For example, when zinc reacts with dilute hydrochloric acid, hydrogen gas is evolved: Zn + 2HCl → ZnCl₂ + H₂. When lead nitrate reacts with potassium iodide, a yellow precipitate of lead iodide forms. A temperature change is observed when quicklime reacts with water. These observations help identify that a chemical change has occurred. Thus, chemical reactions can often be recognized through observable physical or energy changes This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 124 Marks 1. Chemical Reactions and Equations Explain combination, decomposition, displacement and double displacement reactions with balanced examples Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A combination reaction occurs when two or more substances form a single product. Example: CaO + H₂O → Ca(OH)₂. A decomposition reaction is the opposite, where one compound breaks into simpler substances; calcium carbonate decomposes on heating: CaCO₃ → CaO + CO₂. In a displacement reaction, a more reactive element displaces a less reactive element from its compound, such as Zn + CuSO₄ → ZnSO₄ + Cu. A double displacement reaction involves exchange of ions between two compounds. For example, Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃, where yellow PbI₂ precipitates. These reactions are classified according to how reactants rearrange to form products A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 134 Marks 1. Chemical Reactions and Equations Explain oxidation and reduction and show why they occur simultaneously in a redox reaction Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Oxidation and reduction are complementary processes. Oxidation can be understood as gain of oxygen, loss of hydrogen, or loss of electrons, while reduction involves loss of oxygen, gain of hydrogen, or gain of electrons. Both processes occur simultaneously in a redox reaction. For example, in CuO + H₂ → Cu + H₂O, copper oxide loses oxygen and is reduced to copper, whereas hydrogen gains oxygen and is oxidised to water. In terms of electrons, a substance that loses electrons is oxidised and another substance gains those electrons and is reduced. Therefore, oxidation cannot normally occur independently of reduction in a redox process Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 144 Marks 1. Chemical Reactions and Equations Explain corrosion, its effects and the major methods used to prevent it Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Corrosion is the gradual deterioration of a metal due to chemical or electrochemical reactions with substances in the environment. Iron reacts with oxygen and moisture to form rust. Corrosion weakens structures, damages machines and causes economic losses. It can be prevented by isolating the metal from air and moisture or by making the metal less reactive. Common methods include painting, oiling or greasing, galvanisation, electroplating and alloying. Galvanisation protects iron by coating it with zinc. Stainless steel resists corrosion because it contains elements such as chromium that form a protective surface layer. Therefore, controlling contact with oxygen and moisture is an important strategy for preventing corrosion A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 154 Marks 1. Chemical Reactions and Equations Explain rancidity and discuss practical methods for preventing it in food materials Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Rancidity is the oxidation of fats and oils in food, which produces unpleasant smell and taste. It reduces food quality and may make food unsuitable for consumption. Exposure to oxygen, light, heat and moisture can accelerate the process. Rancidity can be prevented by storing food in airtight containers, refrigeration, adding suitable antioxidants and using vacuum or inert-gas packaging. For example, packets of chips are often filled with nitrogen to reduce contact between the oil and oxygen. Keeping food away from excessive heat and direct sunlight also slows oxidation. Thus, limiting oxygen and other favourable conditions helps preserve the freshness and quality of fatty foods For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 164 Marks 1. Chemical Reactions and Equations Analyze the characteristics of a chemical reaction and explain how different observations provide evidence of chemical change Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A chemical reaction is a process in which one or more substances change into new substances with different properties. Important observations include change in colour, evolution of a gas, formation of a precipitate, change in temperature, and change in state. For example, when zinc reacts with dilute hydrochloric acid, hydrogen gas is evolved: Zn + 2HCl → ZnCl₂ + H₂. When lead nitrate reacts with potassium iodide, a yellow precipitate of lead iodide forms. A temperature change is observed when quicklime reacts with water. These observations help identify that a chemical change has occurred. Thus, chemical reactions can often be recognized through observable physical or energy changes This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 174 Marks 1. Chemical Reactions and Equations Explain combination, decomposition, displacement and double displacement reactions with balanced examples Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A combination reaction occurs when two or more substances form a single product. Example: CaO + H₂O → Ca(OH)₂. A decomposition reaction is the opposite, where one compound breaks into simpler substances; calcium carbonate decomposes on heating: CaCO₃ → CaO + CO₂. In a displacement reaction, a more reactive element displaces a less reactive element from its compound, such as Zn + CuSO₄ → ZnSO₄ + Cu. A double displacement reaction involves exchange of ions between two compounds. For example, Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃, where yellow PbI₂ precipitates. These reactions are classified according to how reactants rearrange to form products A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 184 Marks 1. Chemical Reactions and Equations Explain oxidation and reduction and show why they occur simultaneously in a redox reaction Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Oxidation and reduction are complementary processes. Oxidation can be understood as gain of oxygen, loss of hydrogen, or loss of electrons, while reduction involves loss of oxygen, gain of hydrogen, or gain of electrons. Both processes occur simultaneously in a redox reaction. For example, in CuO + H₂ → Cu + H₂O, copper oxide loses oxygen and is reduced to copper, whereas hydrogen gains oxygen and is oxidised to water. In terms of electrons, a substance that loses electrons is oxidised and another substance gains those electrons and is reduced. Therefore, oxidation cannot normally occur independently of reduction in a redox process Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 194 Marks 1. Chemical Reactions and Equations Explain corrosion, its effects and the major methods used to prevent it Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Corrosion is the gradual deterioration of a metal due to chemical or electrochemical reactions with substances in the environment. Iron reacts with oxygen and moisture to form rust. Corrosion weakens structures, damages machines and causes economic losses. It can be prevented by isolating the metal from air and moisture or by making the metal less reactive. Common methods include painting, oiling or greasing, galvanisation, electroplating and alloying. Galvanisation protects iron by coating it with zinc. Stainless steel resists corrosion because it contains elements such as chromium that form a protective surface layer. Therefore, controlling contact with oxygen and moisture is an important strategy for preventing corrosion A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 204 Marks 1. Chemical Reactions and Equations Explain rancidity and discuss practical methods for preventing it in food materials Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Rancidity is the oxidation of fats and oils in food, which produces unpleasant smell and taste. It reduces food quality and may make food unsuitable for consumption. Exposure to oxygen, light, heat and moisture can accelerate the process. Rancidity can be prevented by storing food in airtight containers, refrigeration, adding suitable antioxidants and using vacuum or inert-gas packaging. For example, packets of chips are often filled with nitrogen to reduce contact between the oil and oxygen. Keeping food away from excessive heat and direct sunlight also slows oxidation. Thus, limiting oxygen and other favourable conditions helps preserve the freshness and quality of fatty foods For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 214 Marks 1. Chemical Reactions and Equations Analyze the characteristics of a chemical reaction and explain how different observations provide evidence of chemical change Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A chemical reaction is a process in which one or more substances change into new substances with different properties. Important observations include change in colour, evolution of a gas, formation of a precipitate, change in temperature, and change in state. For example, when zinc reacts with dilute hydrochloric acid, hydrogen gas is evolved: Zn + 2HCl → ZnCl₂ + H₂. When lead nitrate reacts with potassium iodide, a yellow precipitate of lead iodide forms. A temperature change is observed when quicklime reacts with water. These observations help identify that a chemical change has occurred. Thus, chemical reactions can often be recognized through observable physical or energy changes This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 224 Marks 1. Chemical Reactions and Equations Explain combination, decomposition, displacement and double displacement reactions with balanced examples Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A combination reaction occurs when two or more substances form a single product. Example: CaO + H₂O → Ca(OH)₂. A decomposition reaction is the opposite, where one compound breaks into simpler substances; calcium carbonate decomposes on heating: CaCO₃ → CaO + CO₂. In a displacement reaction, a more reactive element displaces a less reactive element from its compound, such as Zn + CuSO₄ → ZnSO₄ + Cu. A double displacement reaction involves exchange of ions between two compounds. For example, Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃, where yellow PbI₂ precipitates. These reactions are classified according to how reactants rearrange to form products A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 234 Marks 1. Chemical Reactions and Equations Explain oxidation and reduction and show why they occur simultaneously in a redox reaction Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Oxidation and reduction are complementary processes. Oxidation can be understood as gain of oxygen, loss of hydrogen, or loss of electrons, while reduction involves loss of oxygen, gain of hydrogen, or gain of electrons. Both processes occur simultaneously in a redox reaction. For example, in CuO + H₂ → Cu + H₂O, copper oxide loses oxygen and is reduced to copper, whereas hydrogen gains oxygen and is oxidised to water. In terms of electrons, a substance that loses electrons is oxidised and another substance gains those electrons and is reduced. Therefore, oxidation cannot normally occur independently of reduction in a redox process Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 244 Marks 1. Chemical Reactions and Equations Explain corrosion, its effects and the major methods used to prevent it Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Corrosion is the gradual deterioration of a metal due to chemical or electrochemical reactions with substances in the environment. Iron reacts with oxygen and moisture to form rust. Corrosion weakens structures, damages machines and causes economic losses. It can be prevented by isolating the metal from air and moisture or by making the metal less reactive. Common methods include painting, oiling or greasing, galvanisation, electroplating and alloying. Galvanisation protects iron by coating it with zinc. Stainless steel resists corrosion because it contains elements such as chromium that form a protective surface layer. Therefore, controlling contact with oxygen and moisture is an important strategy for preventing corrosion A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 254 Marks 1. Chemical Reactions and Equations Explain rancidity and discuss practical methods for preventing it in food materials Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Rancidity is the oxidation of fats and oils in food, which produces unpleasant smell and taste. It reduces food quality and may make food unsuitable for consumption. Exposure to oxygen, light, heat and moisture can accelerate the process. Rancidity can be prevented by storing food in airtight containers, refrigeration, adding suitable antioxidants and using vacuum or inert-gas packaging. For example, packets of chips are often filled with nitrogen to reduce contact between the oil and oxygen. Keeping food away from excessive heat and direct sunlight also slows oxidation. Thus, limiting oxygen and other favourable conditions helps preserve the freshness and quality of fatty foods For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 264 Marks 1. Chemical Reactions and Equations Analyze the characteristics of a chemical reaction and explain how different observations provide evidence of chemical change Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A chemical reaction is a process in which one or more substances change into new substances with different properties. Important observations include change in colour, evolution of a gas, formation of a precipitate, change in temperature, and change in state. For example, when zinc reacts with dilute hydrochloric acid, hydrogen gas is evolved: Zn + 2HCl → ZnCl₂ + H₂. When lead nitrate reacts with potassium iodide, a yellow precipitate of lead iodide forms. A temperature change is observed when quicklime reacts with water. These observations help identify that a chemical change has occurred. Thus, chemical reactions can often be recognized through observable physical or energy changes This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 274 Marks 1. Chemical Reactions and Equations Explain combination, decomposition, displacement and double displacement reactions with balanced examples Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A combination reaction occurs when two or more substances form a single product. Example: CaO + H₂O → Ca(OH)₂. A decomposition reaction is the opposite, where one compound breaks into simpler substances; calcium carbonate decomposes on heating: CaCO₃ → CaO + CO₂. In a displacement reaction, a more reactive element displaces a less reactive element from its compound, such as Zn + CuSO₄ → ZnSO₄ + Cu. A double displacement reaction involves exchange of ions between two compounds. For example, Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃, where yellow PbI₂ precipitates. These reactions are classified according to how reactants rearrange to form products A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 284 Marks 1. Chemical Reactions and Equations Explain oxidation and reduction and show why they occur simultaneously in a redox reaction Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Oxidation and reduction are complementary processes. Oxidation can be understood as gain of oxygen, loss of hydrogen, or loss of electrons, while reduction involves loss of oxygen, gain of hydrogen, or gain of electrons. Both processes occur simultaneously in a redox reaction. For example, in CuO + H₂ → Cu + H₂O, copper oxide loses oxygen and is reduced to copper, whereas hydrogen gains oxygen and is oxidised to water. In terms of electrons, a substance that loses electrons is oxidised and another substance gains those electrons and is reduced. Therefore, oxidation cannot normally occur independently of reduction in a redox process Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 294 Marks 1. Chemical Reactions and Equations Explain corrosion, its effects and the major methods used to prevent it Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Corrosion is the gradual deterioration of a metal due to chemical or electrochemical reactions with substances in the environment. Iron reacts with oxygen and moisture to form rust. Corrosion weakens structures, damages machines and causes economic losses. It can be prevented by isolating the metal from air and moisture or by making the metal less reactive. Common methods include painting, oiling or greasing, galvanisation, electroplating and alloying. Galvanisation protects iron by coating it with zinc. Stainless steel resists corrosion because it contains elements such as chromium that form a protective surface layer. Therefore, controlling contact with oxygen and moisture is an important strategy for preventing corrosion A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 304 Marks 1. Chemical Reactions and Equations Explain rancidity and discuss practical methods for preventing it in food materials Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Rancidity is the oxidation of fats and oils in food, which produces unpleasant smell and taste. It reduces food quality and may make food unsuitable for consumption. Exposure to oxygen, light, heat and moisture can accelerate the process. Rancidity can be prevented by storing food in airtight containers, refrigeration, adding suitable antioxidants and using vacuum or inert-gas packaging. For example, packets of chips are often filled with nitrogen to reduce contact between the oil and oxygen. Keeping food away from excessive heat and direct sunlight also slows oxidation. Thus, limiting oxygen and other favourable conditions helps preserve the freshness and quality of fatty foods For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 314 Marks 1. Chemical Reactions and Equations Analyze the characteristics of a chemical reaction and explain how different observations provide evidence of chemical change Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A chemical reaction is a process in which one or more substances change into new substances with different properties. Important observations include change in colour, evolution of a gas, formation of a precipitate, change in temperature, and change in state. For example, when zinc reacts with dilute hydrochloric acid, hydrogen gas is evolved: Zn + 2HCl → ZnCl₂ + H₂. When lead nitrate reacts with potassium iodide, a yellow precipitate of lead iodide forms. A temperature change is observed when quicklime reacts with water. These observations help identify that a chemical change has occurred. Thus, chemical reactions can often be recognized through observable physical or energy changes This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 324 Marks 1. Chemical Reactions and Equations Explain combination, decomposition, displacement and double displacement reactions with balanced examples Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A combination reaction occurs when two or more substances form a single product. Example: CaO + H₂O → Ca(OH)₂. A decomposition reaction is the opposite, where one compound breaks into simpler substances; calcium carbonate decomposes on heating: CaCO₃ → CaO + CO₂. In a displacement reaction, a more reactive element displaces a less reactive element from its compound, such as Zn + CuSO₄ → ZnSO₄ + Cu. A double displacement reaction involves exchange of ions between two compounds. For example, Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃, where yellow PbI₂ precipitates. These reactions are classified according to how reactants rearrange to form products A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 334 Marks 1. Chemical Reactions and Equations Explain oxidation and reduction and show why they occur simultaneously in a redox reaction Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Oxidation and reduction are complementary processes. Oxidation can be understood as gain of oxygen, loss of hydrogen, or loss of electrons, while reduction involves loss of oxygen, gain of hydrogen, or gain of electrons. Both processes occur simultaneously in a redox reaction. For example, in CuO + H₂ → Cu + H₂O, copper oxide loses oxygen and is reduced to copper, whereas hydrogen gains oxygen and is oxidised to water. In terms of electrons, a substance that loses electrons is oxidised and another substance gains those electrons and is reduced. Therefore, oxidation cannot normally occur independently of reduction in a redox process Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 344 Marks 1. Chemical Reactions and Equations Explain corrosion, its effects and the major methods used to prevent it Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Corrosion is the gradual deterioration of a metal due to chemical or electrochemical reactions with substances in the environment. Iron reacts with oxygen and moisture to form rust. Corrosion weakens structures, damages machines and causes economic losses. It can be prevented by isolating the metal from air and moisture or by making the metal less reactive. Common methods include painting, oiling or greasing, galvanisation, electroplating and alloying. Galvanisation protects iron by coating it with zinc. Stainless steel resists corrosion because it contains elements such as chromium that form a protective surface layer. Therefore, controlling contact with oxygen and moisture is an important strategy for preventing corrosion A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 354 Marks 1. Chemical Reactions and Equations Explain rancidity and discuss practical methods for preventing it in food materials Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Rancidity is the oxidation of fats and oils in food, which produces unpleasant smell and taste. It reduces food quality and may make food unsuitable for consumption. Exposure to oxygen, light, heat and moisture can accelerate the process. Rancidity can be prevented by storing food in airtight containers, refrigeration, adding suitable antioxidants and using vacuum or inert-gas packaging. For example, packets of chips are often filled with nitrogen to reduce contact between the oil and oxygen. Keeping food away from excessive heat and direct sunlight also slows oxidation. Thus, limiting oxygen and other favourable conditions helps preserve the freshness and quality of fatty foods For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 364 Marks 1. Chemical Reactions and Equations Analyze the characteristics of a chemical reaction and explain how different observations provide evidence of chemical change Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A chemical reaction is a process in which one or more substances change into new substances with different properties. Important observations include change in colour, evolution of a gas, formation of a precipitate, change in temperature, and change in state. For example, when zinc reacts with dilute hydrochloric acid, hydrogen gas is evolved: Zn + 2HCl → ZnCl₂ + H₂. When lead nitrate reacts with potassium iodide, a yellow precipitate of lead iodide forms. A temperature change is observed when quicklime reacts with water. These observations help identify that a chemical change has occurred. Thus, chemical reactions can often be recognized through observable physical or energy changes This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 374 Marks 2. Acids, Bases and Salts Explain the chemical properties of acids with suitable balanced equations and examples. Click to View Answer ▼
Answer:
Acids show several characteristic chemical properties. They react with active metals to produce salt and hydrogen gas, for example Zn + 2HCl → ZnCl₂ + H₂. They react with metal carbonates to form salt, water and carbon dioxide: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. Acids also neutralise bases to form salt and water, such as HCl + NaOH → NaCl + H₂O. In aqueous solution, acids produce hydrogen ions, which are responsible for acidic behaviour. Acids also react with some metal oxides because these oxides are basic in nature. These reactions explain many practical applications of acids in laboratories and industries.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 384 Marks 2. Acids, Bases and Salts Explain the pH scale and discuss its importance in digestion, tooth decay and soil management. Click to View Answer ▼
Answer:
The pH scale is used to express how acidic or basic an aqueous solution is. It generally ranges from 0 to 14. A pH below 7 indicates an acidic solution, 7 indicates neutrality and values above 7 indicate basicity. pH is important in the human digestive system because the stomach contains hydrochloric acid that provides a suitable acidic environment for digestion. Tooth decay begins when acids produced by bacteria lower the pH around teeth. Toothpaste is generally basic and helps neutralise these acids. Soil pH also affects plant growth because different crops require suitable pH ranges. Therefore, maintaining an appropriate pH is important in biological and agricultural processes.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 394 Marks 2. Acids, Bases and Salts Explain the preparation, properties and uses of baking soda. Click to View Answer ▼
Answer:
Baking soda is sodium hydrogen carbonate, with the formula NaHCO₃. It can be produced industrially during the Solvay process. On heating, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. The carbon dioxide released helps cakes and bread rise when baking soda is used with a suitable acidic ingredient. Baking soda is also used as an antacid because it can neutralise excess stomach acid. It is useful in some fire extinguishers because carbon dioxide is produced during its reaction. Thus, the chemical properties of sodium hydrogen carbonate make it useful in cooking, medicine and fire safety.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 404 Marks 2. Acids, Bases and Salts Explain the preparation and important uses of washing soda and relate its properties to these uses. Click to View Answer ▼
Answer:
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. Sodium carbonate can be obtained from sodium hydrogen carbonate by heating, followed by crystallisation with water. Washing soda is an alkaline salt and is useful for removing permanent hardness of water because carbonate ions react with calcium and magnesium ions to form insoluble carbonates. It is also used in glass, soap and paper industries. In homes, it can be used as a cleaning agent. Its alkaline nature and ability to react with certain dissolved salts make it valuable in industrial and domestic applications. Thus, its chemical properties are directly connected with its practical uses.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 414 Marks 2. Acids, Bases and Salts Explain the chemical properties of acids with suitable balanced equations and examples Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Acids show several characteristic chemical properties. They react with active metals to produce salt and hydrogen gas, for example Zn + 2HCl → ZnCl₂ + H₂. They react with metal carbonates to form salt, water and carbon dioxide: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. Acids also neutralise bases to form salt and water, such as HCl + NaOH → NaCl + H₂O. In aqueous solution, acids produce hydrogen ions, which are responsible for acidic behaviour. Acids also react with some metal oxides because these oxides are basic in nature. These reactions explain many practical applications of acids in laboratories and industries This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 424 Marks 2. Acids, Bases and Salts Explain the pH scale and discuss its importance in digestion, tooth decay and soil management Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
The pH scale is used to express how acidic or basic an aqueous solution is. It generally ranges from 0 to 14. A pH below 7 indicates an acidic solution, 7 indicates neutrality and values above 7 indicate basicity. pH is important in the human digestive system because the stomach contains hydrochloric acid that provides a suitable acidic environment for digestion. Tooth decay begins when acids produced by bacteria lower the pH around teeth. Toothpaste is generally basic and helps neutralise these acids. Soil pH also affects plant growth because different crops require suitable pH ranges. Therefore, maintaining an appropriate pH is important in biological and agricultural processes A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 434 Marks 2. Acids, Bases and Salts Explain the preparation, properties and uses of baking soda Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Baking soda is sodium hydrogen carbonate, with the formula NaHCO₃. It can be produced industrially during the Solvay process. On heating, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. The carbon dioxide released helps cakes and bread rise when baking soda is used with a suitable acidic ingredient. Baking soda is also used as an antacid because it can neutralise excess stomach acid. It is useful in some fire extinguishers because carbon dioxide is produced during its reaction. Thus, the chemical properties of sodium hydrogen carbonate make it useful in cooking, medicine and fire safety Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 444 Marks 2. Acids, Bases and Salts Explain the preparation and important uses of washing soda and relate its properties to these uses Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. Sodium carbonate can be obtained from sodium hydrogen carbonate by heating, followed by crystallisation with water. Washing soda is an alkaline salt and is useful for removing permanent hardness of water because carbonate ions react with calcium and magnesium ions to form insoluble carbonates. It is also used in glass, soap and paper industries. In homes, it can be used as a cleaning agent. Its alkaline nature and ability to react with certain dissolved salts make it valuable in industrial and domestic applications. Thus, its chemical properties are directly connected with its practical uses A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 454 Marks 2. Acids, Bases and Salts Explain the chemical properties of acids with suitable balanced equations and examples Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Acids show several characteristic chemical properties. They react with active metals to produce salt and hydrogen gas, for example Zn + 2HCl → ZnCl₂ + H₂. They react with metal carbonates to form salt, water and carbon dioxide: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. Acids also neutralise bases to form salt and water, such as HCl + NaOH → NaCl + H₂O. In aqueous solution, acids produce hydrogen ions, which are responsible for acidic behaviour. Acids also react with some metal oxides because these oxides are basic in nature. These reactions explain many practical applications of acids in laboratories and industries For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 464 Marks 2. Acids, Bases and Salts Explain the pH scale and discuss its importance in digestion, tooth decay and soil management Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The pH scale is used to express how acidic or basic an aqueous solution is. It generally ranges from 0 to 14. A pH below 7 indicates an acidic solution, 7 indicates neutrality and values above 7 indicate basicity. pH is important in the human digestive system because the stomach contains hydrochloric acid that provides a suitable acidic environment for digestion. Tooth decay begins when acids produced by bacteria lower the pH around teeth. Toothpaste is generally basic and helps neutralise these acids. Soil pH also affects plant growth because different crops require suitable pH ranges. Therefore, maintaining an appropriate pH is important in biological and agricultural processes This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 474 Marks 2. Acids, Bases and Salts Explain the preparation, properties and uses of baking soda Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Baking soda is sodium hydrogen carbonate, with the formula NaHCO₃. It can be produced industrially during the Solvay process. On heating, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. The carbon dioxide released helps cakes and bread rise when baking soda is used with a suitable acidic ingredient. Baking soda is also used as an antacid because it can neutralise excess stomach acid. It is useful in some fire extinguishers because carbon dioxide is produced during its reaction. Thus, the chemical properties of sodium hydrogen carbonate make it useful in cooking, medicine and fire safety A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 484 Marks 2. Acids, Bases and Salts Explain the preparation and important uses of washing soda and relate its properties to these uses Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. Sodium carbonate can be obtained from sodium hydrogen carbonate by heating, followed by crystallisation with water. Washing soda is an alkaline salt and is useful for removing permanent hardness of water because carbonate ions react with calcium and magnesium ions to form insoluble carbonates. It is also used in glass, soap and paper industries. In homes, it can be used as a cleaning agent. Its alkaline nature and ability to react with certain dissolved salts make it valuable in industrial and domestic applications. Thus, its chemical properties are directly connected with its practical uses Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 494 Marks 2. Acids, Bases and Salts Explain the chemical properties of acids with suitable balanced equations and examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Acids show several characteristic chemical properties. They react with active metals to produce salt and hydrogen gas, for example Zn + 2HCl → ZnCl₂ + H₂. They react with metal carbonates to form salt, water and carbon dioxide: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. Acids also neutralise bases to form salt and water, such as HCl + NaOH → NaCl + H₂O. In aqueous solution, acids produce hydrogen ions, which are responsible for acidic behaviour. Acids also react with some metal oxides because these oxides are basic in nature. These reactions explain many practical applications of acids in laboratories and industries A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 504 Marks 2. Acids, Bases and Salts Explain the pH scale and discuss its importance in digestion, tooth decay and soil management Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The pH scale is used to express how acidic or basic an aqueous solution is. It generally ranges from 0 to 14. A pH below 7 indicates an acidic solution, 7 indicates neutrality and values above 7 indicate basicity. pH is important in the human digestive system because the stomach contains hydrochloric acid that provides a suitable acidic environment for digestion. Tooth decay begins when acids produced by bacteria lower the pH around teeth. Toothpaste is generally basic and helps neutralise these acids. Soil pH also affects plant growth because different crops require suitable pH ranges. Therefore, maintaining an appropriate pH is important in biological and agricultural processes For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 514 Marks 2. Acids, Bases and Salts Explain the preparation, properties and uses of baking soda Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Baking soda is sodium hydrogen carbonate, with the formula NaHCO₃. It can be produced industrially during the Solvay process. On heating, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. The carbon dioxide released helps cakes and bread rise when baking soda is used with a suitable acidic ingredient. Baking soda is also used as an antacid because it can neutralise excess stomach acid. It is useful in some fire extinguishers because carbon dioxide is produced during its reaction. Thus, the chemical properties of sodium hydrogen carbonate make it useful in cooking, medicine and fire safety This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 524 Marks 2. Acids, Bases and Salts Explain the preparation and important uses of washing soda and relate its properties to these uses Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. Sodium carbonate can be obtained from sodium hydrogen carbonate by heating, followed by crystallisation with water. Washing soda is an alkaline salt and is useful for removing permanent hardness of water because carbonate ions react with calcium and magnesium ions to form insoluble carbonates. It is also used in glass, soap and paper industries. In homes, it can be used as a cleaning agent. Its alkaline nature and ability to react with certain dissolved salts make it valuable in industrial and domestic applications. Thus, its chemical properties are directly connected with its practical uses A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 534 Marks 2. Acids, Bases and Salts Explain the chemical properties of acids with suitable balanced equations and examples Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Acids show several characteristic chemical properties. They react with active metals to produce salt and hydrogen gas, for example Zn + 2HCl → ZnCl₂ + H₂. They react with metal carbonates to form salt, water and carbon dioxide: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. Acids also neutralise bases to form salt and water, such as HCl + NaOH → NaCl + H₂O. In aqueous solution, acids produce hydrogen ions, which are responsible for acidic behaviour. Acids also react with some metal oxides because these oxides are basic in nature. These reactions explain many practical applications of acids in laboratories and industries Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 544 Marks 2. Acids, Bases and Salts Explain the pH scale and discuss its importance in digestion, tooth decay and soil management Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The pH scale is used to express how acidic or basic an aqueous solution is. It generally ranges from 0 to 14. A pH below 7 indicates an acidic solution, 7 indicates neutrality and values above 7 indicate basicity. pH is important in the human digestive system because the stomach contains hydrochloric acid that provides a suitable acidic environment for digestion. Tooth decay begins when acids produced by bacteria lower the pH around teeth. Toothpaste is generally basic and helps neutralise these acids. Soil pH also affects plant growth because different crops require suitable pH ranges. Therefore, maintaining an appropriate pH is important in biological and agricultural processes A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 554 Marks 2. Acids, Bases and Salts Explain the preparation, properties and uses of baking soda Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Baking soda is sodium hydrogen carbonate, with the formula NaHCO₃. It can be produced industrially during the Solvay process. On heating, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. The carbon dioxide released helps cakes and bread rise when baking soda is used with a suitable acidic ingredient. Baking soda is also used as an antacid because it can neutralise excess stomach acid. It is useful in some fire extinguishers because carbon dioxide is produced during its reaction. Thus, the chemical properties of sodium hydrogen carbonate make it useful in cooking, medicine and fire safety For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 564 Marks 2. Acids, Bases and Salts Explain the preparation and important uses of washing soda and relate its properties to these uses Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. Sodium carbonate can be obtained from sodium hydrogen carbonate by heating, followed by crystallisation with water. Washing soda is an alkaline salt and is useful for removing permanent hardness of water because carbonate ions react with calcium and magnesium ions to form insoluble carbonates. It is also used in glass, soap and paper industries. In homes, it can be used as a cleaning agent. Its alkaline nature and ability to react with certain dissolved salts make it valuable in industrial and domestic applications. Thus, its chemical properties are directly connected with its practical uses This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 574 Marks 2. Acids, Bases and Salts Explain the chemical properties of acids with suitable balanced equations and examples Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Acids show several characteristic chemical properties. They react with active metals to produce salt and hydrogen gas, for example Zn + 2HCl → ZnCl₂ + H₂. They react with metal carbonates to form salt, water and carbon dioxide: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. Acids also neutralise bases to form salt and water, such as HCl + NaOH → NaCl + H₂O. In aqueous solution, acids produce hydrogen ions, which are responsible for acidic behaviour. Acids also react with some metal oxides because these oxides are basic in nature. These reactions explain many practical applications of acids in laboratories and industries A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 584 Marks 2. Acids, Bases and Salts Explain the pH scale and discuss its importance in digestion, tooth decay and soil management Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The pH scale is used to express how acidic or basic an aqueous solution is. It generally ranges from 0 to 14. A pH below 7 indicates an acidic solution, 7 indicates neutrality and values above 7 indicate basicity. pH is important in the human digestive system because the stomach contains hydrochloric acid that provides a suitable acidic environment for digestion. Tooth decay begins when acids produced by bacteria lower the pH around teeth. Toothpaste is generally basic and helps neutralise these acids. Soil pH also affects plant growth because different crops require suitable pH ranges. Therefore, maintaining an appropriate pH is important in biological and agricultural processes Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 594 Marks 2. Acids, Bases and Salts Explain the preparation, properties and uses of baking soda Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Baking soda is sodium hydrogen carbonate, with the formula NaHCO₃. It can be produced industrially during the Solvay process. On heating, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. The carbon dioxide released helps cakes and bread rise when baking soda is used with a suitable acidic ingredient. Baking soda is also used as an antacid because it can neutralise excess stomach acid. It is useful in some fire extinguishers because carbon dioxide is produced during its reaction. Thus, the chemical properties of sodium hydrogen carbonate make it useful in cooking, medicine and fire safety A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 604 Marks 2. Acids, Bases and Salts Explain the preparation and important uses of washing soda and relate its properties to these uses Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. Sodium carbonate can be obtained from sodium hydrogen carbonate by heating, followed by crystallisation with water. Washing soda is an alkaline salt and is useful for removing permanent hardness of water because carbonate ions react with calcium and magnesium ions to form insoluble carbonates. It is also used in glass, soap and paper industries. In homes, it can be used as a cleaning agent. Its alkaline nature and ability to react with certain dissolved salts make it valuable in industrial and domestic applications. Thus, its chemical properties are directly connected with its practical uses For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 614 Marks 2. Acids, Bases and Salts Explain the chemical properties of acids with suitable balanced equations and examples Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Acids show several characteristic chemical properties. They react with active metals to produce salt and hydrogen gas, for example Zn + 2HCl → ZnCl₂ + H₂. They react with metal carbonates to form salt, water and carbon dioxide: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. Acids also neutralise bases to form salt and water, such as HCl + NaOH → NaCl + H₂O. In aqueous solution, acids produce hydrogen ions, which are responsible for acidic behaviour. Acids also react with some metal oxides because these oxides are basic in nature. These reactions explain many practical applications of acids in laboratories and industries This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 624 Marks 2. Acids, Bases and Salts Explain the pH scale and discuss its importance in digestion, tooth decay and soil management Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
The pH scale is used to express how acidic or basic an aqueous solution is. It generally ranges from 0 to 14. A pH below 7 indicates an acidic solution, 7 indicates neutrality and values above 7 indicate basicity. pH is important in the human digestive system because the stomach contains hydrochloric acid that provides a suitable acidic environment for digestion. Tooth decay begins when acids produced by bacteria lower the pH around teeth. Toothpaste is generally basic and helps neutralise these acids. Soil pH also affects plant growth because different crops require suitable pH ranges. Therefore, maintaining an appropriate pH is important in biological and agricultural processes A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 634 Marks 2. Acids, Bases and Salts Explain the preparation, properties and uses of baking soda Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Baking soda is sodium hydrogen carbonate, with the formula NaHCO₃. It can be produced industrially during the Solvay process. On heating, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. The carbon dioxide released helps cakes and bread rise when baking soda is used with a suitable acidic ingredient. Baking soda is also used as an antacid because it can neutralise excess stomach acid. It is useful in some fire extinguishers because carbon dioxide is produced during its reaction. Thus, the chemical properties of sodium hydrogen carbonate make it useful in cooking, medicine and fire safety Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 644 Marks 2. Acids, Bases and Salts Explain the preparation and important uses of washing soda and relate its properties to these uses Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. Sodium carbonate can be obtained from sodium hydrogen carbonate by heating, followed by crystallisation with water. Washing soda is an alkaline salt and is useful for removing permanent hardness of water because carbonate ions react with calcium and magnesium ions to form insoluble carbonates. It is also used in glass, soap and paper industries. In homes, it can be used as a cleaning agent. Its alkaline nature and ability to react with certain dissolved salts make it valuable in industrial and domestic applications. Thus, its chemical properties are directly connected with its practical uses A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 654 Marks 2. Acids, Bases and Salts Explain the chemical properties of acids with suitable balanced equations and examples Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Acids show several characteristic chemical properties. They react with active metals to produce salt and hydrogen gas, for example Zn + 2HCl → ZnCl₂ + H₂. They react with metal carbonates to form salt, water and carbon dioxide: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. Acids also neutralise bases to form salt and water, such as HCl + NaOH → NaCl + H₂O. In aqueous solution, acids produce hydrogen ions, which are responsible for acidic behaviour. Acids also react with some metal oxides because these oxides are basic in nature. These reactions explain many practical applications of acids in laboratories and industries For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 664 Marks 2. Acids, Bases and Salts Explain the pH scale and discuss its importance in digestion, tooth decay and soil management Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The pH scale is used to express how acidic or basic an aqueous solution is. It generally ranges from 0 to 14. A pH below 7 indicates an acidic solution, 7 indicates neutrality and values above 7 indicate basicity. pH is important in the human digestive system because the stomach contains hydrochloric acid that provides a suitable acidic environment for digestion. Tooth decay begins when acids produced by bacteria lower the pH around teeth. Toothpaste is generally basic and helps neutralise these acids. Soil pH also affects plant growth because different crops require suitable pH ranges. Therefore, maintaining an appropriate pH is important in biological and agricultural processes This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 674 Marks 2. Acids, Bases and Salts Explain the preparation, properties and uses of baking soda Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Baking soda is sodium hydrogen carbonate, with the formula NaHCO₃. It can be produced industrially during the Solvay process. On heating, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. The carbon dioxide released helps cakes and bread rise when baking soda is used with a suitable acidic ingredient. Baking soda is also used as an antacid because it can neutralise excess stomach acid. It is useful in some fire extinguishers because carbon dioxide is produced during its reaction. Thus, the chemical properties of sodium hydrogen carbonate make it useful in cooking, medicine and fire safety A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 684 Marks 2. Acids, Bases and Salts Explain the preparation and important uses of washing soda and relate its properties to these uses Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. Sodium carbonate can be obtained from sodium hydrogen carbonate by heating, followed by crystallisation with water. Washing soda is an alkaline salt and is useful for removing permanent hardness of water because carbonate ions react with calcium and magnesium ions to form insoluble carbonates. It is also used in glass, soap and paper industries. In homes, it can be used as a cleaning agent. Its alkaline nature and ability to react with certain dissolved salts make it valuable in industrial and domestic applications. Thus, its chemical properties are directly connected with its practical uses Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 694 Marks 2. Acids, Bases and Salts Explain the chemical properties of acids with suitable balanced equations and examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Acids show several characteristic chemical properties. They react with active metals to produce salt and hydrogen gas, for example Zn + 2HCl → ZnCl₂ + H₂. They react with metal carbonates to form salt, water and carbon dioxide: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂. Acids also neutralise bases to form salt and water, such as HCl + NaOH → NaCl + H₂O. In aqueous solution, acids produce hydrogen ions, which are responsible for acidic behaviour. Acids also react with some metal oxides because these oxides are basic in nature. These reactions explain many practical applications of acids in laboratories and industries A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 704 Marks 2. Acids, Bases and Salts Explain the pH scale and discuss its importance in digestion, tooth decay and soil management Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The pH scale is used to express how acidic or basic an aqueous solution is. It generally ranges from 0 to 14. A pH below 7 indicates an acidic solution, 7 indicates neutrality and values above 7 indicate basicity. pH is important in the human digestive system because the stomach contains hydrochloric acid that provides a suitable acidic environment for digestion. Tooth decay begins when acids produced by bacteria lower the pH around teeth. Toothpaste is generally basic and helps neutralise these acids. Soil pH also affects plant growth because different crops require suitable pH ranges. Therefore, maintaining an appropriate pH is important in biological and agricultural processes For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 714 Marks 2. Acids, Bases and Salts Explain the preparation, properties and uses of baking soda Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Baking soda is sodium hydrogen carbonate, with the formula NaHCO₃. It can be produced industrially during the Solvay process. On heating, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. The carbon dioxide released helps cakes and bread rise when baking soda is used with a suitable acidic ingredient. Baking soda is also used as an antacid because it can neutralise excess stomach acid. It is useful in some fire extinguishers because carbon dioxide is produced during its reaction. Thus, the chemical properties of sodium hydrogen carbonate make it useful in cooking, medicine and fire safety This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 724 Marks 2. Acids, Bases and Salts Explain the preparation and important uses of washing soda and relate its properties to these uses Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. Sodium carbonate can be obtained from sodium hydrogen carbonate by heating, followed by crystallisation with water. Washing soda is an alkaline salt and is useful for removing permanent hardness of water because carbonate ions react with calcium and magnesium ions to form insoluble carbonates. It is also used in glass, soap and paper industries. In homes, it can be used as a cleaning agent. Its alkaline nature and ability to react with certain dissolved salts make it valuable in industrial and domestic applications. Thus, its chemical properties are directly connected with its practical uses A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 734 Marks 3. Metals and Non-metals Compare the physical and chemical properties of metals and non-metals and explain important exceptions. Click to View Answer ▼
Answer:
Metals are generally lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are generally dull, brittle in solid form and poor conductors. However, important exceptions exist: graphite, a form of carbon, conducts electricity, while mercury is a liquid metal. Chemically, metals tend to lose electrons and form positive ions, whereas non-metals tend to gain or share electrons. Metals generally form basic oxides, while non-metal oxides are often acidic or neutral. Metals can react with acids to release hydrogen if they are above hydrogen in the reactivity series. These trends help explain their behaviour in chemical reactions and their practical uses.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 744 Marks 3. Metals and Non-metals Explain the formation of ionic compounds using electron transfer and discuss their properties. Click to View Answer ▼
Answer:
Ionic compounds are formed when electrons are transferred from one atom to another, usually from a metal to a non-metal. For example, sodium has one valence electron and chlorine needs one electron to complete its outer shell. Sodium loses one electron to form Na⁺, while chlorine gains it to form Cl⁻. The electrostatic attraction between these oppositely charged ions forms sodium chloride. Ionic compounds generally have high melting and boiling points because strong forces hold their ions together. They conduct electricity in molten or aqueous states because ions are free to move, but usually do not conduct in the solid state. They are often soluble in water and crystalline in structure.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 754 Marks 3. Metals and Non-metals Explain the extraction of metals according to their position in the reactivity series. Click to View Answer ▼
Answer:
The method of extracting a metal depends on its reactivity. Highly reactive metals such as sodium, potassium and calcium cannot be extracted by reducing their compounds with carbon; they are obtained by electrolysis of molten compounds. Moderately reactive metals such as zinc, iron and lead are generally extracted by converting their ores into oxides and then reducing the oxides using carbon or carbon monoxide. For example, ZnO + C → Zn + CO. Low-reactivity metals such as copper, silver and gold may occur in native form or require simpler extraction methods. Thus, the reactivity series helps determine the appropriate extraction technique and reducing agent.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 764 Marks 3. Metals and Non-metals Explain the reactivity series and use it to predict displacement reactions with examples. Click to View Answer ▼
Answer:
The reactivity series arranges metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc is more reactive than copper, so zinc displaces copper from copper sulphate: Zn + CuSO₄ → ZnSO₄ + Cu. Similarly, iron can displace copper from copper sulphate because iron is above copper in the series. However, copper cannot displace zinc from zinc sulphate because copper is less reactive. The series is useful not only for predicting displacement reactions but also for selecting extraction methods and understanding how metals react with water, acids and oxygen.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 774 Marks 3. Metals and Non-metals Compare the physical and chemical properties of metals and non-metals and explain important exceptions Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Metals are generally lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are generally dull, brittle in solid form and poor conductors. However, important exceptions exist: graphite, a form of carbon, conducts electricity, while mercury is a liquid metal. Chemically, metals tend to lose electrons and form positive ions, whereas non-metals tend to gain or share electrons. Metals generally form basic oxides, while non-metal oxides are often acidic or neutral. Metals can react with acids to release hydrogen if they are above hydrogen in the reactivity series. These trends help explain their behaviour in chemical reactions and their practical uses This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 784 Marks 3. Metals and Non-metals Explain the formation of ionic compounds using electron transfer and discuss their properties Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Ionic compounds are formed when electrons are transferred from one atom to another, usually from a metal to a non-metal. For example, sodium has one valence electron and chlorine needs one electron to complete its outer shell. Sodium loses one electron to form Na⁺, while chlorine gains it to form Cl⁻. The electrostatic attraction between these oppositely charged ions forms sodium chloride. Ionic compounds generally have high melting and boiling points because strong forces hold their ions together. They conduct electricity in molten or aqueous states because ions are free to move, but usually do not conduct in the solid state. They are often soluble in water and crystalline in structure A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 794 Marks 3. Metals and Non-metals Explain the extraction of metals according to their position in the reactivity series Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The method of extracting a metal depends on its reactivity. Highly reactive metals such as sodium, potassium and calcium cannot be extracted by reducing their compounds with carbon; they are obtained by electrolysis of molten compounds. Moderately reactive metals such as zinc, iron and lead are generally extracted by converting their ores into oxides and then reducing the oxides using carbon or carbon monoxide. For example, ZnO + C → Zn + CO. Low-reactivity metals such as copper, silver and gold may occur in native form or require simpler extraction methods. Thus, the reactivity series helps determine the appropriate extraction technique and reducing agent Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 804 Marks 3. Metals and Non-metals Explain the reactivity series and use it to predict displacement reactions with examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The reactivity series arranges metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc is more reactive than copper, so zinc displaces copper from copper sulphate: Zn + CuSO₄ → ZnSO₄ + Cu. Similarly, iron can displace copper from copper sulphate because iron is above copper in the series. However, copper cannot displace zinc from zinc sulphate because copper is less reactive. The series is useful not only for predicting displacement reactions but also for selecting extraction methods and understanding how metals react with water, acids and oxygen A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 814 Marks 3. Metals and Non-metals Compare the physical and chemical properties of metals and non-metals and explain important exceptions Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Metals are generally lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are generally dull, brittle in solid form and poor conductors. However, important exceptions exist: graphite, a form of carbon, conducts electricity, while mercury is a liquid metal. Chemically, metals tend to lose electrons and form positive ions, whereas non-metals tend to gain or share electrons. Metals generally form basic oxides, while non-metal oxides are often acidic or neutral. Metals can react with acids to release hydrogen if they are above hydrogen in the reactivity series. These trends help explain their behaviour in chemical reactions and their practical uses For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 824 Marks 3. Metals and Non-metals Explain the formation of ionic compounds using electron transfer and discuss their properties Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Ionic compounds are formed when electrons are transferred from one atom to another, usually from a metal to a non-metal. For example, sodium has one valence electron and chlorine needs one electron to complete its outer shell. Sodium loses one electron to form Na⁺, while chlorine gains it to form Cl⁻. The electrostatic attraction between these oppositely charged ions forms sodium chloride. Ionic compounds generally have high melting and boiling points because strong forces hold their ions together. They conduct electricity in molten or aqueous states because ions are free to move, but usually do not conduct in the solid state. They are often soluble in water and crystalline in structure This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 834 Marks 3. Metals and Non-metals Explain the extraction of metals according to their position in the reactivity series Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
The method of extracting a metal depends on its reactivity. Highly reactive metals such as sodium, potassium and calcium cannot be extracted by reducing their compounds with carbon; they are obtained by electrolysis of molten compounds. Moderately reactive metals such as zinc, iron and lead are generally extracted by converting their ores into oxides and then reducing the oxides using carbon or carbon monoxide. For example, ZnO + C → Zn + CO. Low-reactivity metals such as copper, silver and gold may occur in native form or require simpler extraction methods. Thus, the reactivity series helps determine the appropriate extraction technique and reducing agent A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 844 Marks 3. Metals and Non-metals Explain the reactivity series and use it to predict displacement reactions with examples Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The reactivity series arranges metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc is more reactive than copper, so zinc displaces copper from copper sulphate: Zn + CuSO₄ → ZnSO₄ + Cu. Similarly, iron can displace copper from copper sulphate because iron is above copper in the series. However, copper cannot displace zinc from zinc sulphate because copper is less reactive. The series is useful not only for predicting displacement reactions but also for selecting extraction methods and understanding how metals react with water, acids and oxygen Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 854 Marks 3. Metals and Non-metals Compare the physical and chemical properties of metals and non-metals and explain important exceptions Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Metals are generally lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are generally dull, brittle in solid form and poor conductors. However, important exceptions exist: graphite, a form of carbon, conducts electricity, while mercury is a liquid metal. Chemically, metals tend to lose electrons and form positive ions, whereas non-metals tend to gain or share electrons. Metals generally form basic oxides, while non-metal oxides are often acidic or neutral. Metals can react with acids to release hydrogen if they are above hydrogen in the reactivity series. These trends help explain their behaviour in chemical reactions and their practical uses A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 864 Marks 3. Metals and Non-metals Explain the formation of ionic compounds using electron transfer and discuss their properties Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Ionic compounds are formed when electrons are transferred from one atom to another, usually from a metal to a non-metal. For example, sodium has one valence electron and chlorine needs one electron to complete its outer shell. Sodium loses one electron to form Na⁺, while chlorine gains it to form Cl⁻. The electrostatic attraction between these oppositely charged ions forms sodium chloride. Ionic compounds generally have high melting and boiling points because strong forces hold their ions together. They conduct electricity in molten or aqueous states because ions are free to move, but usually do not conduct in the solid state. They are often soluble in water and crystalline in structure For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 874 Marks 3. Metals and Non-metals Explain the extraction of metals according to their position in the reactivity series Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The method of extracting a metal depends on its reactivity. Highly reactive metals such as sodium, potassium and calcium cannot be extracted by reducing their compounds with carbon; they are obtained by electrolysis of molten compounds. Moderately reactive metals such as zinc, iron and lead are generally extracted by converting their ores into oxides and then reducing the oxides using carbon or carbon monoxide. For example, ZnO + C → Zn + CO. Low-reactivity metals such as copper, silver and gold may occur in native form or require simpler extraction methods. Thus, the reactivity series helps determine the appropriate extraction technique and reducing agent This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 884 Marks 3. Metals and Non-metals Explain the reactivity series and use it to predict displacement reactions with examples Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
The reactivity series arranges metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc is more reactive than copper, so zinc displaces copper from copper sulphate: Zn + CuSO₄ → ZnSO₄ + Cu. Similarly, iron can displace copper from copper sulphate because iron is above copper in the series. However, copper cannot displace zinc from zinc sulphate because copper is less reactive. The series is useful not only for predicting displacement reactions but also for selecting extraction methods and understanding how metals react with water, acids and oxygen A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 894 Marks 3. Metals and Non-metals Compare the physical and chemical properties of metals and non-metals and explain important exceptions Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Metals are generally lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are generally dull, brittle in solid form and poor conductors. However, important exceptions exist: graphite, a form of carbon, conducts electricity, while mercury is a liquid metal. Chemically, metals tend to lose electrons and form positive ions, whereas non-metals tend to gain or share electrons. Metals generally form basic oxides, while non-metal oxides are often acidic or neutral. Metals can react with acids to release hydrogen if they are above hydrogen in the reactivity series. These trends help explain their behaviour in chemical reactions and their practical uses Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 904 Marks 3. Metals and Non-metals Explain the formation of ionic compounds using electron transfer and discuss their properties Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Ionic compounds are formed when electrons are transferred from one atom to another, usually from a metal to a non-metal. For example, sodium has one valence electron and chlorine needs one electron to complete its outer shell. Sodium loses one electron to form Na⁺, while chlorine gains it to form Cl⁻. The electrostatic attraction between these oppositely charged ions forms sodium chloride. Ionic compounds generally have high melting and boiling points because strong forces hold their ions together. They conduct electricity in molten or aqueous states because ions are free to move, but usually do not conduct in the solid state. They are often soluble in water and crystalline in structure A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 914 Marks 3. Metals and Non-metals Explain the extraction of metals according to their position in the reactivity series Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The method of extracting a metal depends on its reactivity. Highly reactive metals such as sodium, potassium and calcium cannot be extracted by reducing their compounds with carbon; they are obtained by electrolysis of molten compounds. Moderately reactive metals such as zinc, iron and lead are generally extracted by converting their ores into oxides and then reducing the oxides using carbon or carbon monoxide. For example, ZnO + C → Zn + CO. Low-reactivity metals such as copper, silver and gold may occur in native form or require simpler extraction methods. Thus, the reactivity series helps determine the appropriate extraction technique and reducing agent For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 924 Marks 3. Metals and Non-metals Explain the reactivity series and use it to predict displacement reactions with examples Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The reactivity series arranges metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc is more reactive than copper, so zinc displaces copper from copper sulphate: Zn + CuSO₄ → ZnSO₄ + Cu. Similarly, iron can displace copper from copper sulphate because iron is above copper in the series. However, copper cannot displace zinc from zinc sulphate because copper is less reactive. The series is useful not only for predicting displacement reactions but also for selecting extraction methods and understanding how metals react with water, acids and oxygen This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 934 Marks 3. Metals and Non-metals Compare the physical and chemical properties of metals and non-metals and explain important exceptions Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Metals are generally lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are generally dull, brittle in solid form and poor conductors. However, important exceptions exist: graphite, a form of carbon, conducts electricity, while mercury is a liquid metal. Chemically, metals tend to lose electrons and form positive ions, whereas non-metals tend to gain or share electrons. Metals generally form basic oxides, while non-metal oxides are often acidic or neutral. Metals can react with acids to release hydrogen if they are above hydrogen in the reactivity series. These trends help explain their behaviour in chemical reactions and their practical uses A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 944 Marks 3. Metals and Non-metals Explain the formation of ionic compounds using electron transfer and discuss their properties Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Ionic compounds are formed when electrons are transferred from one atom to another, usually from a metal to a non-metal. For example, sodium has one valence electron and chlorine needs one electron to complete its outer shell. Sodium loses one electron to form Na⁺, while chlorine gains it to form Cl⁻. The electrostatic attraction between these oppositely charged ions forms sodium chloride. Ionic compounds generally have high melting and boiling points because strong forces hold their ions together. They conduct electricity in molten or aqueous states because ions are free to move, but usually do not conduct in the solid state. They are often soluble in water and crystalline in structure Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 954 Marks 3. Metals and Non-metals Explain the extraction of metals according to their position in the reactivity series Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The method of extracting a metal depends on its reactivity. Highly reactive metals such as sodium, potassium and calcium cannot be extracted by reducing their compounds with carbon; they are obtained by electrolysis of molten compounds. Moderately reactive metals such as zinc, iron and lead are generally extracted by converting their ores into oxides and then reducing the oxides using carbon or carbon monoxide. For example, ZnO + C → Zn + CO. Low-reactivity metals such as copper, silver and gold may occur in native form or require simpler extraction methods. Thus, the reactivity series helps determine the appropriate extraction technique and reducing agent A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 964 Marks 3. Metals and Non-metals Explain the reactivity series and use it to predict displacement reactions with examples Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The reactivity series arranges metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc is more reactive than copper, so zinc displaces copper from copper sulphate: Zn + CuSO₄ → ZnSO₄ + Cu. Similarly, iron can displace copper from copper sulphate because iron is above copper in the series. However, copper cannot displace zinc from zinc sulphate because copper is less reactive. The series is useful not only for predicting displacement reactions but also for selecting extraction methods and understanding how metals react with water, acids and oxygen For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 974 Marks 3. Metals and Non-metals Compare the physical and chemical properties of metals and non-metals and explain important exceptions Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Metals are generally lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are generally dull, brittle in solid form and poor conductors. However, important exceptions exist: graphite, a form of carbon, conducts electricity, while mercury is a liquid metal. Chemically, metals tend to lose electrons and form positive ions, whereas non-metals tend to gain or share electrons. Metals generally form basic oxides, while non-metal oxides are often acidic or neutral. Metals can react with acids to release hydrogen if they are above hydrogen in the reactivity series. These trends help explain their behaviour in chemical reactions and their practical uses This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 984 Marks 3. Metals and Non-metals Explain the formation of ionic compounds using electron transfer and discuss their properties Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Ionic compounds are formed when electrons are transferred from one atom to another, usually from a metal to a non-metal. For example, sodium has one valence electron and chlorine needs one electron to complete its outer shell. Sodium loses one electron to form Na⁺, while chlorine gains it to form Cl⁻. The electrostatic attraction between these oppositely charged ions forms sodium chloride. Ionic compounds generally have high melting and boiling points because strong forces hold their ions together. They conduct electricity in molten or aqueous states because ions are free to move, but usually do not conduct in the solid state. They are often soluble in water and crystalline in structure A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 994 Marks 3. Metals and Non-metals Explain the extraction of metals according to their position in the reactivity series Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The method of extracting a metal depends on its reactivity. Highly reactive metals such as sodium, potassium and calcium cannot be extracted by reducing their compounds with carbon; they are obtained by electrolysis of molten compounds. Moderately reactive metals such as zinc, iron and lead are generally extracted by converting their ores into oxides and then reducing the oxides using carbon or carbon monoxide. For example, ZnO + C → Zn + CO. Low-reactivity metals such as copper, silver and gold may occur in native form or require simpler extraction methods. Thus, the reactivity series helps determine the appropriate extraction technique and reducing agent Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1004 Marks 3. Metals and Non-metals Explain the reactivity series and use it to predict displacement reactions with examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The reactivity series arranges metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc is more reactive than copper, so zinc displaces copper from copper sulphate: Zn + CuSO₄ → ZnSO₄ + Cu. Similarly, iron can displace copper from copper sulphate because iron is above copper in the series. However, copper cannot displace zinc from zinc sulphate because copper is less reactive. The series is useful not only for predicting displacement reactions but also for selecting extraction methods and understanding how metals react with water, acids and oxygen A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1014 Marks 3. Metals and Non-metals Compare the physical and chemical properties of metals and non-metals and explain important exceptions Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Metals are generally lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are generally dull, brittle in solid form and poor conductors. However, important exceptions exist: graphite, a form of carbon, conducts electricity, while mercury is a liquid metal. Chemically, metals tend to lose electrons and form positive ions, whereas non-metals tend to gain or share electrons. Metals generally form basic oxides, while non-metal oxides are often acidic or neutral. Metals can react with acids to release hydrogen if they are above hydrogen in the reactivity series. These trends help explain their behaviour in chemical reactions and their practical uses For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1024 Marks 3. Metals and Non-metals Explain the formation of ionic compounds using electron transfer and discuss their properties Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Ionic compounds are formed when electrons are transferred from one atom to another, usually from a metal to a non-metal. For example, sodium has one valence electron and chlorine needs one electron to complete its outer shell. Sodium loses one electron to form Na⁺, while chlorine gains it to form Cl⁻. The electrostatic attraction between these oppositely charged ions forms sodium chloride. Ionic compounds generally have high melting and boiling points because strong forces hold their ions together. They conduct electricity in molten or aqueous states because ions are free to move, but usually do not conduct in the solid state. They are often soluble in water and crystalline in structure This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1034 Marks 3. Metals and Non-metals Explain the extraction of metals according to their position in the reactivity series Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
The method of extracting a metal depends on its reactivity. Highly reactive metals such as sodium, potassium and calcium cannot be extracted by reducing their compounds with carbon; they are obtained by electrolysis of molten compounds. Moderately reactive metals such as zinc, iron and lead are generally extracted by converting their ores into oxides and then reducing the oxides using carbon or carbon monoxide. For example, ZnO + C → Zn + CO. Low-reactivity metals such as copper, silver and gold may occur in native form or require simpler extraction methods. Thus, the reactivity series helps determine the appropriate extraction technique and reducing agent A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1044 Marks 3. Metals and Non-metals Explain the reactivity series and use it to predict displacement reactions with examples Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The reactivity series arranges metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc is more reactive than copper, so zinc displaces copper from copper sulphate: Zn + CuSO₄ → ZnSO₄ + Cu. Similarly, iron can displace copper from copper sulphate because iron is above copper in the series. However, copper cannot displace zinc from zinc sulphate because copper is less reactive. The series is useful not only for predicting displacement reactions but also for selecting extraction methods and understanding how metals react with water, acids and oxygen Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1054 Marks 3. Metals and Non-metals Compare the physical and chemical properties of metals and non-metals and explain important exceptions Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Metals are generally lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are generally dull, brittle in solid form and poor conductors. However, important exceptions exist: graphite, a form of carbon, conducts electricity, while mercury is a liquid metal. Chemically, metals tend to lose electrons and form positive ions, whereas non-metals tend to gain or share electrons. Metals generally form basic oxides, while non-metal oxides are often acidic or neutral. Metals can react with acids to release hydrogen if they are above hydrogen in the reactivity series. These trends help explain their behaviour in chemical reactions and their practical uses A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1064 Marks 3. Metals and Non-metals Explain the formation of ionic compounds using electron transfer and discuss their properties Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Ionic compounds are formed when electrons are transferred from one atom to another, usually from a metal to a non-metal. For example, sodium has one valence electron and chlorine needs one electron to complete its outer shell. Sodium loses one electron to form Na⁺, while chlorine gains it to form Cl⁻. The electrostatic attraction between these oppositely charged ions forms sodium chloride. Ionic compounds generally have high melting and boiling points because strong forces hold their ions together. They conduct electricity in molten or aqueous states because ions are free to move, but usually do not conduct in the solid state. They are often soluble in water and crystalline in structure For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1074 Marks 3. Metals and Non-metals Explain the extraction of metals according to their position in the reactivity series Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The method of extracting a metal depends on its reactivity. Highly reactive metals such as sodium, potassium and calcium cannot be extracted by reducing their compounds with carbon; they are obtained by electrolysis of molten compounds. Moderately reactive metals such as zinc, iron and lead are generally extracted by converting their ores into oxides and then reducing the oxides using carbon or carbon monoxide. For example, ZnO + C → Zn + CO. Low-reactivity metals such as copper, silver and gold may occur in native form or require simpler extraction methods. Thus, the reactivity series helps determine the appropriate extraction technique and reducing agent This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1084 Marks 3. Metals and Non-metals Explain the reactivity series and use it to predict displacement reactions with examples Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
The reactivity series arranges metals from most reactive to least reactive. A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc is more reactive than copper, so zinc displaces copper from copper sulphate: Zn + CuSO₄ → ZnSO₄ + Cu. Similarly, iron can displace copper from copper sulphate because iron is above copper in the series. However, copper cannot displace zinc from zinc sulphate because copper is less reactive. The series is useful not only for predicting displacement reactions but also for selecting extraction methods and understanding how metals react with water, acids and oxygen A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1094 Marks 4. Carbon and Its Compounds Explain why carbon forms a very large number of compounds, using catenation and tetravalency. Click to View Answer ▼
Answer:
Carbon forms a huge variety of compounds mainly because of catenation and tetravalency. Catenation is the ability of carbon atoms to bond strongly with one another, producing straight chains, branched chains and rings. Tetravalency means that carbon has four valence electrons and can form four covalent bonds with carbon, hydrogen, oxygen, nitrogen and other elements. Carbon-carbon bonds are sufficiently strong and stable to form many structures. For example, hydrocarbons such as methane, ethane and propane differ in carbon-chain length. Carbon also forms single, double and triple bonds. These properties allow carbon to form millions of compounds, making carbon chemistry central to living organisms and many industrial materials.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1104 Marks 4. Carbon and Its Compounds Explain homologous series and show how its characteristics help in studying organic compounds. Click to View Answer ▼
Answer:
A homologous series is a family of organic compounds having the same functional group and general formula, with successive members differing by a –CH₂– unit. Members have similar chemical properties because they contain the same functional group, while their physical properties show gradual changes with increasing molecular mass. For example, the alcohol series includes methanol, ethanol and propanol. Each successive member differs by CH₂. Their similar reactions are associated with the common –OH functional group. The systematic nature of homologous series makes it easier to predict molecular formulae, physical trends and chemical behaviour of related organic compounds.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1114 Marks 4. Carbon and Its Compounds Explain the cleansing action of soap and why soap becomes less effective in hard water. Click to View Answer ▼
Answer:
Soap molecules contain a hydrophilic end that interacts with water and a hydrophobic hydrocarbon end that interacts with oil and grease. In water, soap molecules arrange themselves into structures called micelles, with the hydrocarbon tails directed inward around oily dirt and the ionic ends facing water. Agitation helps detach grease, which is then suspended in water and washed away. In hard water, calcium and magnesium ions react with soap to form insoluble scum. This consumes soap and reduces lather, making cleaning less effective. Synthetic detergents are generally more effective in hard water because their calcium and magnesium salts remain soluble.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1124 Marks 4. Carbon and Its Compounds Explain addition and substitution reactions of carbon compounds with suitable examples. Click to View Answer ▼
Answer:
An addition reaction occurs when atoms are added across a double or triple bond of an unsaturated compound. For example, ethene reacts with hydrogen in the presence of a catalyst to form ethane: C₂H₄ + H₂ → C₂H₆. This reaction is used in hydrogenation of vegetable oils. A substitution reaction occurs when one atom or group in a saturated compound is replaced by another. For example, methane reacts with chlorine in sunlight to form chloromethane and hydrogen chloride: CH₄ + Cl₂ → CH₃Cl + HCl. Addition reactions are characteristic of unsaturated compounds, while substitution reactions are commonly associated with saturated hydrocarbons.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1134 Marks 4. Carbon and Its Compounds Explain esterification and saponification and relate them to everyday applications. Click to View Answer ▼
Answer:
Esterification is the reaction of an alcohol with a carboxylic acid in the presence of a suitable acid catalyst to form an ester and water. For example, ethanol reacts with ethanoic acid to form ethyl ethanoate, which has a pleasant smell: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O. Saponification is the alkaline hydrolysis of an ester, producing an alcohol and the salt of a carboxylic acid. It is important in soap manufacture. Thus, esterification is associated with formation of fragrant esters, while saponification is associated with the chemical basis of soap production.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1144 Marks 4. Carbon and Its Compounds Explain why carbon forms a very large number of compounds, using catenation and tetravalency Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Carbon forms a huge variety of compounds mainly because of catenation and tetravalency. Catenation is the ability of carbon atoms to bond strongly with one another, producing straight chains, branched chains and rings. Tetravalency means that carbon has four valence electrons and can form four covalent bonds with carbon, hydrogen, oxygen, nitrogen and other elements. Carbon-carbon bonds are sufficiently strong and stable to form many structures. For example, hydrocarbons such as methane, ethane and propane differ in carbon-chain length. Carbon also forms single, double and triple bonds. These properties allow carbon to form millions of compounds, making carbon chemistry central to living organisms and many industrial materials This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1154 Marks 4. Carbon and Its Compounds Explain homologous series and show how its characteristics help in studying organic compounds Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A homologous series is a family of organic compounds having the same functional group and general formula, with successive members differing by a –CH₂– unit. Members have similar chemical properties because they contain the same functional group, while their physical properties show gradual changes with increasing molecular mass. For example, the alcohol series includes methanol, ethanol and propanol. Each successive member differs by CH₂. Their similar reactions are associated with the common –OH functional group. The systematic nature of homologous series makes it easier to predict molecular formulae, physical trends and chemical behaviour of related organic compounds A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1164 Marks 4. Carbon and Its Compounds Explain the cleansing action of soap and why soap becomes less effective in hard water Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Soap molecules contain a hydrophilic end that interacts with water and a hydrophobic hydrocarbon end that interacts with oil and grease. In water, soap molecules arrange themselves into structures called micelles, with the hydrocarbon tails directed inward around oily dirt and the ionic ends facing water. Agitation helps detach grease, which is then suspended in water and washed away. In hard water, calcium and magnesium ions react with soap to form insoluble scum. This consumes soap and reduces lather, making cleaning less effective. Synthetic detergents are generally more effective in hard water because their calcium and magnesium salts remain soluble Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1174 Marks 4. Carbon and Its Compounds Explain addition and substitution reactions of carbon compounds with suitable examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An addition reaction occurs when atoms are added across a double or triple bond of an unsaturated compound. For example, ethene reacts with hydrogen in the presence of a catalyst to form ethane: C₂H₄ + H₂ → C₂H₆. This reaction is used in hydrogenation of vegetable oils. A substitution reaction occurs when one atom or group in a saturated compound is replaced by another. For example, methane reacts with chlorine in sunlight to form chloromethane and hydrogen chloride: CH₄ + Cl₂ → CH₃Cl + HCl. Addition reactions are characteristic of unsaturated compounds, while substitution reactions are commonly associated with saturated hydrocarbons A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1184 Marks 4. Carbon and Its Compounds Explain esterification and saponification and relate them to everyday applications Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Esterification is the reaction of an alcohol with a carboxylic acid in the presence of a suitable acid catalyst to form an ester and water. For example, ethanol reacts with ethanoic acid to form ethyl ethanoate, which has a pleasant smell: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O. Saponification is the alkaline hydrolysis of an ester, producing an alcohol and the salt of a carboxylic acid. It is important in soap manufacture. Thus, esterification is associated with formation of fragrant esters, while saponification is associated with the chemical basis of soap production For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1194 Marks 4. Carbon and Its Compounds Explain why carbon forms a very large number of compounds, using catenation and tetravalency Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Carbon forms a huge variety of compounds mainly because of catenation and tetravalency. Catenation is the ability of carbon atoms to bond strongly with one another, producing straight chains, branched chains and rings. Tetravalency means that carbon has four valence electrons and can form four covalent bonds with carbon, hydrogen, oxygen, nitrogen and other elements. Carbon-carbon bonds are sufficiently strong and stable to form many structures. For example, hydrocarbons such as methane, ethane and propane differ in carbon-chain length. Carbon also forms single, double and triple bonds. These properties allow carbon to form millions of compounds, making carbon chemistry central to living organisms and many industrial materials This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1204 Marks 4. Carbon and Its Compounds Explain homologous series and show how its characteristics help in studying organic compounds Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A homologous series is a family of organic compounds having the same functional group and general formula, with successive members differing by a –CH₂– unit. Members have similar chemical properties because they contain the same functional group, while their physical properties show gradual changes with increasing molecular mass. For example, the alcohol series includes methanol, ethanol and propanol. Each successive member differs by CH₂. Their similar reactions are associated with the common –OH functional group. The systematic nature of homologous series makes it easier to predict molecular formulae, physical trends and chemical behaviour of related organic compounds A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1214 Marks 4. Carbon and Its Compounds Explain the cleansing action of soap and why soap becomes less effective in hard water Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Soap molecules contain a hydrophilic end that interacts with water and a hydrophobic hydrocarbon end that interacts with oil and grease. In water, soap molecules arrange themselves into structures called micelles, with the hydrocarbon tails directed inward around oily dirt and the ionic ends facing water. Agitation helps detach grease, which is then suspended in water and washed away. In hard water, calcium and magnesium ions react with soap to form insoluble scum. This consumes soap and reduces lather, making cleaning less effective. Synthetic detergents are generally more effective in hard water because their calcium and magnesium salts remain soluble Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1224 Marks 4. Carbon and Its Compounds Explain addition and substitution reactions of carbon compounds with suitable examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An addition reaction occurs when atoms are added across a double or triple bond of an unsaturated compound. For example, ethene reacts with hydrogen in the presence of a catalyst to form ethane: C₂H₄ + H₂ → C₂H₆. This reaction is used in hydrogenation of vegetable oils. A substitution reaction occurs when one atom or group in a saturated compound is replaced by another. For example, methane reacts with chlorine in sunlight to form chloromethane and hydrogen chloride: CH₄ + Cl₂ → CH₃Cl + HCl. Addition reactions are characteristic of unsaturated compounds, while substitution reactions are commonly associated with saturated hydrocarbons A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1234 Marks 4. Carbon and Its Compounds Explain esterification and saponification and relate them to everyday applications Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Esterification is the reaction of an alcohol with a carboxylic acid in the presence of a suitable acid catalyst to form an ester and water. For example, ethanol reacts with ethanoic acid to form ethyl ethanoate, which has a pleasant smell: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O. Saponification is the alkaline hydrolysis of an ester, producing an alcohol and the salt of a carboxylic acid. It is important in soap manufacture. Thus, esterification is associated with formation of fragrant esters, while saponification is associated with the chemical basis of soap production For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1244 Marks 4. Carbon and Its Compounds Explain why carbon forms a very large number of compounds, using catenation and tetravalency Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Carbon forms a huge variety of compounds mainly because of catenation and tetravalency. Catenation is the ability of carbon atoms to bond strongly with one another, producing straight chains, branched chains and rings. Tetravalency means that carbon has four valence electrons and can form four covalent bonds with carbon, hydrogen, oxygen, nitrogen and other elements. Carbon-carbon bonds are sufficiently strong and stable to form many structures. For example, hydrocarbons such as methane, ethane and propane differ in carbon-chain length. Carbon also forms single, double and triple bonds. These properties allow carbon to form millions of compounds, making carbon chemistry central to living organisms and many industrial materials This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1254 Marks 4. Carbon and Its Compounds Explain homologous series and show how its characteristics help in studying organic compounds Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A homologous series is a family of organic compounds having the same functional group and general formula, with successive members differing by a –CH₂– unit. Members have similar chemical properties because they contain the same functional group, while their physical properties show gradual changes with increasing molecular mass. For example, the alcohol series includes methanol, ethanol and propanol. Each successive member differs by CH₂. Their similar reactions are associated with the common –OH functional group. The systematic nature of homologous series makes it easier to predict molecular formulae, physical trends and chemical behaviour of related organic compounds A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1264 Marks 4. Carbon and Its Compounds Explain the cleansing action of soap and why soap becomes less effective in hard water Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Soap molecules contain a hydrophilic end that interacts with water and a hydrophobic hydrocarbon end that interacts with oil and grease. In water, soap molecules arrange themselves into structures called micelles, with the hydrocarbon tails directed inward around oily dirt and the ionic ends facing water. Agitation helps detach grease, which is then suspended in water and washed away. In hard water, calcium and magnesium ions react with soap to form insoluble scum. This consumes soap and reduces lather, making cleaning less effective. Synthetic detergents are generally more effective in hard water because their calcium and magnesium salts remain soluble Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1274 Marks 4. Carbon and Its Compounds Explain addition and substitution reactions of carbon compounds with suitable examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An addition reaction occurs when atoms are added across a double or triple bond of an unsaturated compound. For example, ethene reacts with hydrogen in the presence of a catalyst to form ethane: C₂H₄ + H₂ → C₂H₆. This reaction is used in hydrogenation of vegetable oils. A substitution reaction occurs when one atom or group in a saturated compound is replaced by another. For example, methane reacts with chlorine in sunlight to form chloromethane and hydrogen chloride: CH₄ + Cl₂ → CH₃Cl + HCl. Addition reactions are characteristic of unsaturated compounds, while substitution reactions are commonly associated with saturated hydrocarbons A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1284 Marks 4. Carbon and Its Compounds Explain esterification and saponification and relate them to everyday applications Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Esterification is the reaction of an alcohol with a carboxylic acid in the presence of a suitable acid catalyst to form an ester and water. For example, ethanol reacts with ethanoic acid to form ethyl ethanoate, which has a pleasant smell: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O. Saponification is the alkaline hydrolysis of an ester, producing an alcohol and the salt of a carboxylic acid. It is important in soap manufacture. Thus, esterification is associated with formation of fragrant esters, while saponification is associated with the chemical basis of soap production For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1294 Marks 4. Carbon and Its Compounds Explain why carbon forms a very large number of compounds, using catenation and tetravalency Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Carbon forms a huge variety of compounds mainly because of catenation and tetravalency. Catenation is the ability of carbon atoms to bond strongly with one another, producing straight chains, branched chains and rings. Tetravalency means that carbon has four valence electrons and can form four covalent bonds with carbon, hydrogen, oxygen, nitrogen and other elements. Carbon-carbon bonds are sufficiently strong and stable to form many structures. For example, hydrocarbons such as methane, ethane and propane differ in carbon-chain length. Carbon also forms single, double and triple bonds. These properties allow carbon to form millions of compounds, making carbon chemistry central to living organisms and many industrial materials This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1304 Marks 4. Carbon and Its Compounds Explain homologous series and show how its characteristics help in studying organic compounds Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A homologous series is a family of organic compounds having the same functional group and general formula, with successive members differing by a –CH₂– unit. Members have similar chemical properties because they contain the same functional group, while their physical properties show gradual changes with increasing molecular mass. For example, the alcohol series includes methanol, ethanol and propanol. Each successive member differs by CH₂. Their similar reactions are associated with the common –OH functional group. The systematic nature of homologous series makes it easier to predict molecular formulae, physical trends and chemical behaviour of related organic compounds A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1314 Marks 4. Carbon and Its Compounds Explain the cleansing action of soap and why soap becomes less effective in hard water Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Soap molecules contain a hydrophilic end that interacts with water and a hydrophobic hydrocarbon end that interacts with oil and grease. In water, soap molecules arrange themselves into structures called micelles, with the hydrocarbon tails directed inward around oily dirt and the ionic ends facing water. Agitation helps detach grease, which is then suspended in water and washed away. In hard water, calcium and magnesium ions react with soap to form insoluble scum. This consumes soap and reduces lather, making cleaning less effective. Synthetic detergents are generally more effective in hard water because their calcium and magnesium salts remain soluble Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1324 Marks 4. Carbon and Its Compounds Explain addition and substitution reactions of carbon compounds with suitable examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An addition reaction occurs when atoms are added across a double or triple bond of an unsaturated compound. For example, ethene reacts with hydrogen in the presence of a catalyst to form ethane: C₂H₄ + H₂ → C₂H₆. This reaction is used in hydrogenation of vegetable oils. A substitution reaction occurs when one atom or group in a saturated compound is replaced by another. For example, methane reacts with chlorine in sunlight to form chloromethane and hydrogen chloride: CH₄ + Cl₂ → CH₃Cl + HCl. Addition reactions are characteristic of unsaturated compounds, while substitution reactions are commonly associated with saturated hydrocarbons A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1334 Marks 4. Carbon and Its Compounds Explain esterification and saponification and relate them to everyday applications Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Esterification is the reaction of an alcohol with a carboxylic acid in the presence of a suitable acid catalyst to form an ester and water. For example, ethanol reacts with ethanoic acid to form ethyl ethanoate, which has a pleasant smell: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O. Saponification is the alkaline hydrolysis of an ester, producing an alcohol and the salt of a carboxylic acid. It is important in soap manufacture. Thus, esterification is associated with formation of fragrant esters, while saponification is associated with the chemical basis of soap production For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1344 Marks 4. Carbon and Its Compounds Explain why carbon forms a very large number of compounds, using catenation and tetravalency Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Carbon forms a huge variety of compounds mainly because of catenation and tetravalency. Catenation is the ability of carbon atoms to bond strongly with one another, producing straight chains, branched chains and rings. Tetravalency means that carbon has four valence electrons and can form four covalent bonds with carbon, hydrogen, oxygen, nitrogen and other elements. Carbon-carbon bonds are sufficiently strong and stable to form many structures. For example, hydrocarbons such as methane, ethane and propane differ in carbon-chain length. Carbon also forms single, double and triple bonds. These properties allow carbon to form millions of compounds, making carbon chemistry central to living organisms and many industrial materials This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1354 Marks 4. Carbon and Its Compounds Explain homologous series and show how its characteristics help in studying organic compounds Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A homologous series is a family of organic compounds having the same functional group and general formula, with successive members differing by a –CH₂– unit. Members have similar chemical properties because they contain the same functional group, while their physical properties show gradual changes with increasing molecular mass. For example, the alcohol series includes methanol, ethanol and propanol. Each successive member differs by CH₂. Their similar reactions are associated with the common –OH functional group. The systematic nature of homologous series makes it easier to predict molecular formulae, physical trends and chemical behaviour of related organic compounds A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1364 Marks 4. Carbon and Its Compounds Explain the cleansing action of soap and why soap becomes less effective in hard water Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Soap molecules contain a hydrophilic end that interacts with water and a hydrophobic hydrocarbon end that interacts with oil and grease. In water, soap molecules arrange themselves into structures called micelles, with the hydrocarbon tails directed inward around oily dirt and the ionic ends facing water. Agitation helps detach grease, which is then suspended in water and washed away. In hard water, calcium and magnesium ions react with soap to form insoluble scum. This consumes soap and reduces lather, making cleaning less effective. Synthetic detergents are generally more effective in hard water because their calcium and magnesium salts remain soluble Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1374 Marks 4. Carbon and Its Compounds Explain addition and substitution reactions of carbon compounds with suitable examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An addition reaction occurs when atoms are added across a double or triple bond of an unsaturated compound. For example, ethene reacts with hydrogen in the presence of a catalyst to form ethane: C₂H₄ + H₂ → C₂H₆. This reaction is used in hydrogenation of vegetable oils. A substitution reaction occurs when one atom or group in a saturated compound is replaced by another. For example, methane reacts with chlorine in sunlight to form chloromethane and hydrogen chloride: CH₄ + Cl₂ → CH₃Cl + HCl. Addition reactions are characteristic of unsaturated compounds, while substitution reactions are commonly associated with saturated hydrocarbons A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1384 Marks 4. Carbon and Its Compounds Explain esterification and saponification and relate them to everyday applications Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Esterification is the reaction of an alcohol with a carboxylic acid in the presence of a suitable acid catalyst to form an ester and water. For example, ethanol reacts with ethanoic acid to form ethyl ethanoate, which has a pleasant smell: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O. Saponification is the alkaline hydrolysis of an ester, producing an alcohol and the salt of a carboxylic acid. It is important in soap manufacture. Thus, esterification is associated with formation of fragrant esters, while saponification is associated with the chemical basis of soap production For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1394 Marks 4. Carbon and Its Compounds Explain why carbon forms a very large number of compounds, using catenation and tetravalency Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Carbon forms a huge variety of compounds mainly because of catenation and tetravalency. Catenation is the ability of carbon atoms to bond strongly with one another, producing straight chains, branched chains and rings. Tetravalency means that carbon has four valence electrons and can form four covalent bonds with carbon, hydrogen, oxygen, nitrogen and other elements. Carbon-carbon bonds are sufficiently strong and stable to form many structures. For example, hydrocarbons such as methane, ethane and propane differ in carbon-chain length. Carbon also forms single, double and triple bonds. These properties allow carbon to form millions of compounds, making carbon chemistry central to living organisms and many industrial materials This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1404 Marks 4. Carbon and Its Compounds Explain homologous series and show how its characteristics help in studying organic compounds Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A homologous series is a family of organic compounds having the same functional group and general formula, with successive members differing by a –CH₂– unit. Members have similar chemical properties because they contain the same functional group, while their physical properties show gradual changes with increasing molecular mass. For example, the alcohol series includes methanol, ethanol and propanol. Each successive member differs by CH₂. Their similar reactions are associated with the common –OH functional group. The systematic nature of homologous series makes it easier to predict molecular formulae, physical trends and chemical behaviour of related organic compounds A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1414 Marks 4. Carbon and Its Compounds Explain the cleansing action of soap and why soap becomes less effective in hard water Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Soap molecules contain a hydrophilic end that interacts with water and a hydrophobic hydrocarbon end that interacts with oil and grease. In water, soap molecules arrange themselves into structures called micelles, with the hydrocarbon tails directed inward around oily dirt and the ionic ends facing water. Agitation helps detach grease, which is then suspended in water and washed away. In hard water, calcium and magnesium ions react with soap to form insoluble scum. This consumes soap and reduces lather, making cleaning less effective. Synthetic detergents are generally more effective in hard water because their calcium and magnesium salts remain soluble Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1424 Marks 4. Carbon and Its Compounds Explain addition and substitution reactions of carbon compounds with suitable examples Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An addition reaction occurs when atoms are added across a double or triple bond of an unsaturated compound. For example, ethene reacts with hydrogen in the presence of a catalyst to form ethane: C₂H₄ + H₂ → C₂H₆. This reaction is used in hydrogenation of vegetable oils. A substitution reaction occurs when one atom or group in a saturated compound is replaced by another. For example, methane reacts with chlorine in sunlight to form chloromethane and hydrogen chloride: CH₄ + Cl₂ → CH₃Cl + HCl. Addition reactions are characteristic of unsaturated compounds, while substitution reactions are commonly associated with saturated hydrocarbons A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1434 Marks 4. Carbon and Its Compounds Explain esterification and saponification and relate them to everyday applications Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Esterification is the reaction of an alcohol with a carboxylic acid in the presence of a suitable acid catalyst to form an ester and water. For example, ethanol reacts with ethanoic acid to form ethyl ethanoate, which has a pleasant smell: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O. Saponification is the alkaline hydrolysis of an ester, producing an alcohol and the salt of a carboxylic acid. It is important in soap manufacture. Thus, esterification is associated with formation of fragrant esters, while saponification is associated with the chemical basis of soap production For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1444 Marks 4. Carbon and Its Compounds Explain why carbon forms a very large number of compounds, using catenation and tetravalency Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Carbon forms a huge variety of compounds mainly because of catenation and tetravalency. Catenation is the ability of carbon atoms to bond strongly with one another, producing straight chains, branched chains and rings. Tetravalency means that carbon has four valence electrons and can form four covalent bonds with carbon, hydrogen, oxygen, nitrogen and other elements. Carbon-carbon bonds are sufficiently strong and stable to form many structures. For example, hydrocarbons such as methane, ethane and propane differ in carbon-chain length. Carbon also forms single, double and triple bonds. These properties allow carbon to form millions of compounds, making carbon chemistry central to living organisms and many industrial materials This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1454 Marks 5. Life Processes Explain how the human digestive system performs digestion, absorption and assimilation of food. Click to View Answer ▼
Answer:
Digestion begins in the mouth where teeth break food mechanically and saliva starts the digestion of starch. The food passes through the oesophagus into the stomach, where hydrochloric acid provides an acidic medium and enzymes help digest proteins. In the small intestine, bile from the liver helps emulsify fats, while pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats. The digested nutrients are absorbed through villi in the small intestine and transported by blood. Cells use these nutrients for energy, growth and repair; this is assimilation. The large intestine mainly absorbs water and forms faeces. Thus, the digestive system converts complex food into absorbable nutrients.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1464 Marks 5. Life Processes Explain double circulation in humans and show how it maintains efficient oxygen supply. Click to View Answer ▼
Answer:
In humans, blood passes through the heart twice during one complete circulation, so the process is called double circulation. In pulmonary circulation, deoxygenated blood from the body enters the right atrium, moves to the right ventricle and is pumped to the lungs. Oxygenated blood returns to the left atrium and enters the left ventricle. In systemic circulation, the left ventricle pumps oxygenated blood to the entire body, while deoxygenated blood returns to the right side of the heart. The separation of oxygenated and deoxygenated blood prevents mixing and allows efficient oxygen delivery. This is important because humans have high energy requirements.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1474 Marks 5. Life Processes Compare aerobic and anaerobic respiration and explain their significance. Click to View Answer ▼
Answer:
Aerobic respiration occurs in the presence of oxygen and generally breaks down glucose completely into carbon dioxide and water, releasing a large amount of energy. It mainly occurs in mitochondria after the initial steps of glucose breakdown. Anaerobic respiration occurs without oxygen and releases less energy. In yeast, glucose is converted into ethanol and carbon dioxide. In human muscle cells during vigorous exercise, insufficient oxygen can lead to formation of lactic acid. Aerobic respiration is more efficient for sustained energy production, whereas anaerobic respiration provides a temporary energy supply when oxygen availability is limited. Both processes begin with the breakdown of glucose.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1484 Marks 5. Life Processes Explain transport of water, minerals and food in plants. Click to View Answer ▼
Answer:
Plants transport water and minerals mainly through xylem and food through phloem. Roots absorb water and mineral ions from the soil. Water moves upward through xylem due to root pressure and, more importantly, transpiration pull generated by evaporation of water from leaves. Cohesion between water molecules helps maintain a continuous water column. Phloem transports prepared food, mainly sugars, from leaves to other parts of the plant. This process is called translocation and requires energy. Unlike xylem transport, phloem movement can occur in different directions depending on where food is produced and where it is needed.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1494 Marks 5. Life Processes Explain the role of the heart, blood and blood vessels in maintaining circulation. Click to View Answer ▼
Answer:
The human circulatory system consists of the heart, blood and blood vessels. The four-chambered heart acts as a muscular pump. The right side receives deoxygenated blood and sends it to the lungs, while the left side receives oxygenated blood and pumps it to the body. Arteries generally carry blood away from the heart and have thick elastic walls. Veins return blood to the heart and contain valves that prevent backflow. Capillaries have thin walls and allow exchange of gases, nutrients and wastes between blood and tissues. Together, these components ensure continuous transport of oxygen, nutrients, hormones and waste products.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1504 Marks 5. Life Processes Explain how the human digestive system performs digestion, absorption and assimilation of food Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Digestion begins in the mouth where teeth break food mechanically and saliva starts the digestion of starch. The food passes through the oesophagus into the stomach, where hydrochloric acid provides an acidic medium and enzymes help digest proteins. In the small intestine, bile from the liver helps emulsify fats, while pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats. The digested nutrients are absorbed through villi in the small intestine and transported by blood. Cells use these nutrients for energy, growth and repair; this is assimilation. The large intestine mainly absorbs water and forms faeces. Thus, the digestive system converts complex food into absorbable nutrients This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1514 Marks 5. Life Processes Explain double circulation in humans and show how it maintains efficient oxygen supply Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In humans, blood passes through the heart twice during one complete circulation, so the process is called double circulation. In pulmonary circulation, deoxygenated blood from the body enters the right atrium, moves to the right ventricle and is pumped to the lungs. Oxygenated blood returns to the left atrium and enters the left ventricle. In systemic circulation, the left ventricle pumps oxygenated blood to the entire body, while deoxygenated blood returns to the right side of the heart. The separation of oxygenated and deoxygenated blood prevents mixing and allows efficient oxygen delivery. This is important because humans have high energy requirements A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1524 Marks 5. Life Processes Compare aerobic and anaerobic respiration and explain their significance Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Aerobic respiration occurs in the presence of oxygen and generally breaks down glucose completely into carbon dioxide and water, releasing a large amount of energy. It mainly occurs in mitochondria after the initial steps of glucose breakdown. Anaerobic respiration occurs without oxygen and releases less energy. In yeast, glucose is converted into ethanol and carbon dioxide. In human muscle cells during vigorous exercise, insufficient oxygen can lead to formation of lactic acid. Aerobic respiration is more efficient for sustained energy production, whereas anaerobic respiration provides a temporary energy supply when oxygen availability is limited. Both processes begin with the breakdown of glucose Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1534 Marks 5. Life Processes Explain transport of water, minerals and food in plants Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Plants transport water and minerals mainly through xylem and food through phloem. Roots absorb water and mineral ions from the soil. Water moves upward through xylem due to root pressure and, more importantly, transpiration pull generated by evaporation of water from leaves. Cohesion between water molecules helps maintain a continuous water column. Phloem transports prepared food, mainly sugars, from leaves to other parts of the plant. This process is called translocation and requires energy. Unlike xylem transport, phloem movement can occur in different directions depending on where food is produced and where it is needed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1544 Marks 5. Life Processes Explain the role of the heart, blood and blood vessels in maintaining circulation Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The human circulatory system consists of the heart, blood and blood vessels. The four-chambered heart acts as a muscular pump. The right side receives deoxygenated blood and sends it to the lungs, while the left side receives oxygenated blood and pumps it to the body. Arteries generally carry blood away from the heart and have thick elastic walls. Veins return blood to the heart and contain valves that prevent backflow. Capillaries have thin walls and allow exchange of gases, nutrients and wastes between blood and tissues. Together, these components ensure continuous transport of oxygen, nutrients, hormones and waste products For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1554 Marks 5. Life Processes Explain how the human digestive system performs digestion, absorption and assimilation of food Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Digestion begins in the mouth where teeth break food mechanically and saliva starts the digestion of starch. The food passes through the oesophagus into the stomach, where hydrochloric acid provides an acidic medium and enzymes help digest proteins. In the small intestine, bile from the liver helps emulsify fats, while pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats. The digested nutrients are absorbed through villi in the small intestine and transported by blood. Cells use these nutrients for energy, growth and repair; this is assimilation. The large intestine mainly absorbs water and forms faeces. Thus, the digestive system converts complex food into absorbable nutrients This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1564 Marks 5. Life Processes Explain double circulation in humans and show how it maintains efficient oxygen supply Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In humans, blood passes through the heart twice during one complete circulation, so the process is called double circulation. In pulmonary circulation, deoxygenated blood from the body enters the right atrium, moves to the right ventricle and is pumped to the lungs. Oxygenated blood returns to the left atrium and enters the left ventricle. In systemic circulation, the left ventricle pumps oxygenated blood to the entire body, while deoxygenated blood returns to the right side of the heart. The separation of oxygenated and deoxygenated blood prevents mixing and allows efficient oxygen delivery. This is important because humans have high energy requirements A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1574 Marks 5. Life Processes Compare aerobic and anaerobic respiration and explain their significance Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Aerobic respiration occurs in the presence of oxygen and generally breaks down glucose completely into carbon dioxide and water, releasing a large amount of energy. It mainly occurs in mitochondria after the initial steps of glucose breakdown. Anaerobic respiration occurs without oxygen and releases less energy. In yeast, glucose is converted into ethanol and carbon dioxide. In human muscle cells during vigorous exercise, insufficient oxygen can lead to formation of lactic acid. Aerobic respiration is more efficient for sustained energy production, whereas anaerobic respiration provides a temporary energy supply when oxygen availability is limited. Both processes begin with the breakdown of glucose Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1584 Marks 5. Life Processes Explain transport of water, minerals and food in plants Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Plants transport water and minerals mainly through xylem and food through phloem. Roots absorb water and mineral ions from the soil. Water moves upward through xylem due to root pressure and, more importantly, transpiration pull generated by evaporation of water from leaves. Cohesion between water molecules helps maintain a continuous water column. Phloem transports prepared food, mainly sugars, from leaves to other parts of the plant. This process is called translocation and requires energy. Unlike xylem transport, phloem movement can occur in different directions depending on where food is produced and where it is needed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1594 Marks 5. Life Processes Explain the role of the heart, blood and blood vessels in maintaining circulation Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The human circulatory system consists of the heart, blood and blood vessels. The four-chambered heart acts as a muscular pump. The right side receives deoxygenated blood and sends it to the lungs, while the left side receives oxygenated blood and pumps it to the body. Arteries generally carry blood away from the heart and have thick elastic walls. Veins return blood to the heart and contain valves that prevent backflow. Capillaries have thin walls and allow exchange of gases, nutrients and wastes between blood and tissues. Together, these components ensure continuous transport of oxygen, nutrients, hormones and waste products For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1604 Marks 5. Life Processes Explain how the human digestive system performs digestion, absorption and assimilation of food Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Digestion begins in the mouth where teeth break food mechanically and saliva starts the digestion of starch. The food passes through the oesophagus into the stomach, where hydrochloric acid provides an acidic medium and enzymes help digest proteins. In the small intestine, bile from the liver helps emulsify fats, while pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats. The digested nutrients are absorbed through villi in the small intestine and transported by blood. Cells use these nutrients for energy, growth and repair; this is assimilation. The large intestine mainly absorbs water and forms faeces. Thus, the digestive system converts complex food into absorbable nutrients This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1614 Marks 5. Life Processes Explain double circulation in humans and show how it maintains efficient oxygen supply Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In humans, blood passes through the heart twice during one complete circulation, so the process is called double circulation. In pulmonary circulation, deoxygenated blood from the body enters the right atrium, moves to the right ventricle and is pumped to the lungs. Oxygenated blood returns to the left atrium and enters the left ventricle. In systemic circulation, the left ventricle pumps oxygenated blood to the entire body, while deoxygenated blood returns to the right side of the heart. The separation of oxygenated and deoxygenated blood prevents mixing and allows efficient oxygen delivery. This is important because humans have high energy requirements A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1624 Marks 5. Life Processes Compare aerobic and anaerobic respiration and explain their significance Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Aerobic respiration occurs in the presence of oxygen and generally breaks down glucose completely into carbon dioxide and water, releasing a large amount of energy. It mainly occurs in mitochondria after the initial steps of glucose breakdown. Anaerobic respiration occurs without oxygen and releases less energy. In yeast, glucose is converted into ethanol and carbon dioxide. In human muscle cells during vigorous exercise, insufficient oxygen can lead to formation of lactic acid. Aerobic respiration is more efficient for sustained energy production, whereas anaerobic respiration provides a temporary energy supply when oxygen availability is limited. Both processes begin with the breakdown of glucose Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1634 Marks 5. Life Processes Explain transport of water, minerals and food in plants Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Plants transport water and minerals mainly through xylem and food through phloem. Roots absorb water and mineral ions from the soil. Water moves upward through xylem due to root pressure and, more importantly, transpiration pull generated by evaporation of water from leaves. Cohesion between water molecules helps maintain a continuous water column. Phloem transports prepared food, mainly sugars, from leaves to other parts of the plant. This process is called translocation and requires energy. Unlike xylem transport, phloem movement can occur in different directions depending on where food is produced and where it is needed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1644 Marks 5. Life Processes Explain the role of the heart, blood and blood vessels in maintaining circulation Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The human circulatory system consists of the heart, blood and blood vessels. The four-chambered heart acts as a muscular pump. The right side receives deoxygenated blood and sends it to the lungs, while the left side receives oxygenated blood and pumps it to the body. Arteries generally carry blood away from the heart and have thick elastic walls. Veins return blood to the heart and contain valves that prevent backflow. Capillaries have thin walls and allow exchange of gases, nutrients and wastes between blood and tissues. Together, these components ensure continuous transport of oxygen, nutrients, hormones and waste products For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1654 Marks 5. Life Processes Explain how the human digestive system performs digestion, absorption and assimilation of food Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Digestion begins in the mouth where teeth break food mechanically and saliva starts the digestion of starch. The food passes through the oesophagus into the stomach, where hydrochloric acid provides an acidic medium and enzymes help digest proteins. In the small intestine, bile from the liver helps emulsify fats, while pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats. The digested nutrients are absorbed through villi in the small intestine and transported by blood. Cells use these nutrients for energy, growth and repair; this is assimilation. The large intestine mainly absorbs water and forms faeces. Thus, the digestive system converts complex food into absorbable nutrients This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1664 Marks 5. Life Processes Explain double circulation in humans and show how it maintains efficient oxygen supply Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In humans, blood passes through the heart twice during one complete circulation, so the process is called double circulation. In pulmonary circulation, deoxygenated blood from the body enters the right atrium, moves to the right ventricle and is pumped to the lungs. Oxygenated blood returns to the left atrium and enters the left ventricle. In systemic circulation, the left ventricle pumps oxygenated blood to the entire body, while deoxygenated blood returns to the right side of the heart. The separation of oxygenated and deoxygenated blood prevents mixing and allows efficient oxygen delivery. This is important because humans have high energy requirements A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1674 Marks 5. Life Processes Compare aerobic and anaerobic respiration and explain their significance Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Aerobic respiration occurs in the presence of oxygen and generally breaks down glucose completely into carbon dioxide and water, releasing a large amount of energy. It mainly occurs in mitochondria after the initial steps of glucose breakdown. Anaerobic respiration occurs without oxygen and releases less energy. In yeast, glucose is converted into ethanol and carbon dioxide. In human muscle cells during vigorous exercise, insufficient oxygen can lead to formation of lactic acid. Aerobic respiration is more efficient for sustained energy production, whereas anaerobic respiration provides a temporary energy supply when oxygen availability is limited. Both processes begin with the breakdown of glucose Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1684 Marks 5. Life Processes Explain transport of water, minerals and food in plants Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Plants transport water and minerals mainly through xylem and food through phloem. Roots absorb water and mineral ions from the soil. Water moves upward through xylem due to root pressure and, more importantly, transpiration pull generated by evaporation of water from leaves. Cohesion between water molecules helps maintain a continuous water column. Phloem transports prepared food, mainly sugars, from leaves to other parts of the plant. This process is called translocation and requires energy. Unlike xylem transport, phloem movement can occur in different directions depending on where food is produced and where it is needed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1694 Marks 5. Life Processes Explain the role of the heart, blood and blood vessels in maintaining circulation Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The human circulatory system consists of the heart, blood and blood vessels. The four-chambered heart acts as a muscular pump. The right side receives deoxygenated blood and sends it to the lungs, while the left side receives oxygenated blood and pumps it to the body. Arteries generally carry blood away from the heart and have thick elastic walls. Veins return blood to the heart and contain valves that prevent backflow. Capillaries have thin walls and allow exchange of gases, nutrients and wastes between blood and tissues. Together, these components ensure continuous transport of oxygen, nutrients, hormones and waste products For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1704 Marks 5. Life Processes Explain how the human digestive system performs digestion, absorption and assimilation of food Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Digestion begins in the mouth where teeth break food mechanically and saliva starts the digestion of starch. The food passes through the oesophagus into the stomach, where hydrochloric acid provides an acidic medium and enzymes help digest proteins. In the small intestine, bile from the liver helps emulsify fats, while pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats. The digested nutrients are absorbed through villi in the small intestine and transported by blood. Cells use these nutrients for energy, growth and repair; this is assimilation. The large intestine mainly absorbs water and forms faeces. Thus, the digestive system converts complex food into absorbable nutrients This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1714 Marks 5. Life Processes Explain double circulation in humans and show how it maintains efficient oxygen supply Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In humans, blood passes through the heart twice during one complete circulation, so the process is called double circulation. In pulmonary circulation, deoxygenated blood from the body enters the right atrium, moves to the right ventricle and is pumped to the lungs. Oxygenated blood returns to the left atrium and enters the left ventricle. In systemic circulation, the left ventricle pumps oxygenated blood to the entire body, while deoxygenated blood returns to the right side of the heart. The separation of oxygenated and deoxygenated blood prevents mixing and allows efficient oxygen delivery. This is important because humans have high energy requirements A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1724 Marks 5. Life Processes Compare aerobic and anaerobic respiration and explain their significance Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Aerobic respiration occurs in the presence of oxygen and generally breaks down glucose completely into carbon dioxide and water, releasing a large amount of energy. It mainly occurs in mitochondria after the initial steps of glucose breakdown. Anaerobic respiration occurs without oxygen and releases less energy. In yeast, glucose is converted into ethanol and carbon dioxide. In human muscle cells during vigorous exercise, insufficient oxygen can lead to formation of lactic acid. Aerobic respiration is more efficient for sustained energy production, whereas anaerobic respiration provides a temporary energy supply when oxygen availability is limited. Both processes begin with the breakdown of glucose Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1734 Marks 5. Life Processes Explain transport of water, minerals and food in plants Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Plants transport water and minerals mainly through xylem and food through phloem. Roots absorb water and mineral ions from the soil. Water moves upward through xylem due to root pressure and, more importantly, transpiration pull generated by evaporation of water from leaves. Cohesion between water molecules helps maintain a continuous water column. Phloem transports prepared food, mainly sugars, from leaves to other parts of the plant. This process is called translocation and requires energy. Unlike xylem transport, phloem movement can occur in different directions depending on where food is produced and where it is needed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1744 Marks 5. Life Processes Explain the role of the heart, blood and blood vessels in maintaining circulation Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The human circulatory system consists of the heart, blood and blood vessels. The four-chambered heart acts as a muscular pump. The right side receives deoxygenated blood and sends it to the lungs, while the left side receives oxygenated blood and pumps it to the body. Arteries generally carry blood away from the heart and have thick elastic walls. Veins return blood to the heart and contain valves that prevent backflow. Capillaries have thin walls and allow exchange of gases, nutrients and wastes between blood and tissues. Together, these components ensure continuous transport of oxygen, nutrients, hormones and waste products For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1754 Marks 5. Life Processes Explain how the human digestive system performs digestion, absorption and assimilation of food Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Digestion begins in the mouth where teeth break food mechanically and saliva starts the digestion of starch. The food passes through the oesophagus into the stomach, where hydrochloric acid provides an acidic medium and enzymes help digest proteins. In the small intestine, bile from the liver helps emulsify fats, while pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats. The digested nutrients are absorbed through villi in the small intestine and transported by blood. Cells use these nutrients for energy, growth and repair; this is assimilation. The large intestine mainly absorbs water and forms faeces. Thus, the digestive system converts complex food into absorbable nutrients This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1764 Marks 5. Life Processes Explain double circulation in humans and show how it maintains efficient oxygen supply Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In humans, blood passes through the heart twice during one complete circulation, so the process is called double circulation. In pulmonary circulation, deoxygenated blood from the body enters the right atrium, moves to the right ventricle and is pumped to the lungs. Oxygenated blood returns to the left atrium and enters the left ventricle. In systemic circulation, the left ventricle pumps oxygenated blood to the entire body, while deoxygenated blood returns to the right side of the heart. The separation of oxygenated and deoxygenated blood prevents mixing and allows efficient oxygen delivery. This is important because humans have high energy requirements A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1774 Marks 5. Life Processes Compare aerobic and anaerobic respiration and explain their significance Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Aerobic respiration occurs in the presence of oxygen and generally breaks down glucose completely into carbon dioxide and water, releasing a large amount of energy. It mainly occurs in mitochondria after the initial steps of glucose breakdown. Anaerobic respiration occurs without oxygen and releases less energy. In yeast, glucose is converted into ethanol and carbon dioxide. In human muscle cells during vigorous exercise, insufficient oxygen can lead to formation of lactic acid. Aerobic respiration is more efficient for sustained energy production, whereas anaerobic respiration provides a temporary energy supply when oxygen availability is limited. Both processes begin with the breakdown of glucose Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1784 Marks 5. Life Processes Explain transport of water, minerals and food in plants Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Plants transport water and minerals mainly through xylem and food through phloem. Roots absorb water and mineral ions from the soil. Water moves upward through xylem due to root pressure and, more importantly, transpiration pull generated by evaporation of water from leaves. Cohesion between water molecules helps maintain a continuous water column. Phloem transports prepared food, mainly sugars, from leaves to other parts of the plant. This process is called translocation and requires energy. Unlike xylem transport, phloem movement can occur in different directions depending on where food is produced and where it is needed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1794 Marks 5. Life Processes Explain the role of the heart, blood and blood vessels in maintaining circulation Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The human circulatory system consists of the heart, blood and blood vessels. The four-chambered heart acts as a muscular pump. The right side receives deoxygenated blood and sends it to the lungs, while the left side receives oxygenated blood and pumps it to the body. Arteries generally carry blood away from the heart and have thick elastic walls. Veins return blood to the heart and contain valves that prevent backflow. Capillaries have thin walls and allow exchange of gases, nutrients and wastes between blood and tissues. Together, these components ensure continuous transport of oxygen, nutrients, hormones and waste products For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1804 Marks 5. Life Processes Explain how the human digestive system performs digestion, absorption and assimilation of food Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Digestion begins in the mouth where teeth break food mechanically and saliva starts the digestion of starch. The food passes through the oesophagus into the stomach, where hydrochloric acid provides an acidic medium and enzymes help digest proteins. In the small intestine, bile from the liver helps emulsify fats, while pancreatic and intestinal enzymes complete digestion of carbohydrates, proteins and fats. The digested nutrients are absorbed through villi in the small intestine and transported by blood. Cells use these nutrients for energy, growth and repair; this is assimilation. The large intestine mainly absorbs water and forms faeces. Thus, the digestive system converts complex food into absorbable nutrients This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1814 Marks 6. Control and Coordination Explain the structure of a neuron and describe how a nerve impulse is transmitted. Click to View Answer ▼
Answer:
A neuron is the basic structural and functional unit of the nervous system. It has dendrites, a cell body and an axon. Dendrites receive information from receptors or other neurons. The cell body processes the signal, and the axon carries the nerve impulse away from the cell body. At the end of an axon, chemicals called neurotransmitters may be released into the synapse, the small gap between neurons. These chemicals stimulate the next neuron or an effector. This arrangement allows information to travel in a coordinated direction. Neurons therefore provide rapid communication between sensory organs, the central nervous system and muscles or glands.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1824 Marks 6. Control and Coordination Explain reflex action and distinguish it from a voluntary action. Click to View Answer ▼
Answer:
A reflex action is a rapid, automatic response to a stimulus that generally occurs without conscious decision. For example, withdrawing the hand from a hot object is a reflex response. The pathway followed by the nerve impulse is called a reflex arc and usually involves a receptor, sensory neuron, relay neuron, motor neuron and effector. Reflex actions help protect the body by reducing response time. Voluntary actions, in contrast, are consciously controlled, such as writing or walking. Although the brain may receive information about a reflex, the immediate response is coordinated through the spinal cord in many common reflexes.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1834 Marks 6. Control and Coordination Explain plant hormones and their role in coordinating growth responses. Click to View Answer ▼
Answer:
Plant hormones are chemical substances that regulate growth and development. Auxin promotes cell growth and is involved in phototropism. When light falls from one side, auxin distribution causes cells on the shaded side to elongate more, making the shoot bend toward light. Gibberellins promote stem growth and seed germination, while cytokinins encourage cell division. Abscisic acid generally inhibits growth and helps plants respond to stress. Ethylene promotes fruit ripening. Unlike animals, plants do not have a nervous system, so chemical coordination through hormones and directional growth responses allows them to respond to environmental conditions.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1844 Marks 6. Control and Coordination Compare nervous and hormonal coordination in humans. Click to View Answer ▼
Answer:
Nervous coordination uses electrical impulses transmitted through neurons and generally produces rapid, short-lived responses. Hormonal coordination uses chemical messengers released by endocrine glands into the blood. Hormones usually act more slowly but their effects may last longer. For example, a reflex action is controlled rapidly through the nervous system, whereas growth and metabolic regulation involve hormones. The two systems work together to maintain coordination and internal balance. The nervous system is particularly useful for immediate responses to stimuli, while hormones regulate processes such as growth, reproduction, metabolism and long-term adaptation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1854 Marks 6. Control and Coordination Explain the role of the brain, spinal cord and peripheral nerves in coordination. Click to View Answer ▼
Answer:
The brain and spinal cord together form the central nervous system. The brain receives sensory information, interprets it and coordinates appropriate responses. Different regions of the brain perform different functions, including thinking, memory, balance and control of involuntary activities. The spinal cord connects the brain with peripheral nerves and also coordinates many reflex actions. Peripheral nerves carry sensory information toward the central nervous system and motor commands toward muscles or glands. This communication network allows the body to detect changes, process information and respond appropriately. Protection by the skull and vertebral column helps safeguard these important nervous structures.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1864 Marks 6. Control and Coordination Explain the structure of a neuron and describe how a nerve impulse is transmitted Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A neuron is the basic structural and functional unit of the nervous system. It has dendrites, a cell body and an axon. Dendrites receive information from receptors or other neurons. The cell body processes the signal, and the axon carries the nerve impulse away from the cell body. At the end of an axon, chemicals called neurotransmitters may be released into the synapse, the small gap between neurons. These chemicals stimulate the next neuron or an effector. This arrangement allows information to travel in a coordinated direction. Neurons therefore provide rapid communication between sensory organs, the central nervous system and muscles or glands This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1874 Marks 6. Control and Coordination Explain reflex action and distinguish it from a voluntary action Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A reflex action is a rapid, automatic response to a stimulus that generally occurs without conscious decision. For example, withdrawing the hand from a hot object is a reflex response. The pathway followed by the nerve impulse is called a reflex arc and usually involves a receptor, sensory neuron, relay neuron, motor neuron and effector. Reflex actions help protect the body by reducing response time. Voluntary actions, in contrast, are consciously controlled, such as writing or walking. Although the brain may receive information about a reflex, the immediate response is coordinated through the spinal cord in many common reflexes A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1884 Marks 6. Control and Coordination Explain plant hormones and their role in coordinating growth responses Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Plant hormones are chemical substances that regulate growth and development. Auxin promotes cell growth and is involved in phototropism. When light falls from one side, auxin distribution causes cells on the shaded side to elongate more, making the shoot bend toward light. Gibberellins promote stem growth and seed germination, while cytokinins encourage cell division. Abscisic acid generally inhibits growth and helps plants respond to stress. Ethylene promotes fruit ripening. Unlike animals, plants do not have a nervous system, so chemical coordination through hormones and directional growth responses allows them to respond to environmental conditions Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1894 Marks 6. Control and Coordination Compare nervous and hormonal coordination in humans Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Nervous coordination uses electrical impulses transmitted through neurons and generally produces rapid, short-lived responses. Hormonal coordination uses chemical messengers released by endocrine glands into the blood. Hormones usually act more slowly but their effects may last longer. For example, a reflex action is controlled rapidly through the nervous system, whereas growth and metabolic regulation involve hormones. The two systems work together to maintain coordination and internal balance. The nervous system is particularly useful for immediate responses to stimuli, while hormones regulate processes such as growth, reproduction, metabolism and long-term adaptation A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1904 Marks 6. Control and Coordination Explain the role of the brain, spinal cord and peripheral nerves in coordination Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The brain and spinal cord together form the central nervous system. The brain receives sensory information, interprets it and coordinates appropriate responses. Different regions of the brain perform different functions, including thinking, memory, balance and control of involuntary activities. The spinal cord connects the brain with peripheral nerves and also coordinates many reflex actions. Peripheral nerves carry sensory information toward the central nervous system and motor commands toward muscles or glands. This communication network allows the body to detect changes, process information and respond appropriately. Protection by the skull and vertebral column helps safeguard these important nervous structures For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1914 Marks 6. Control and Coordination Explain the structure of a neuron and describe how a nerve impulse is transmitted Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A neuron is the basic structural and functional unit of the nervous system. It has dendrites, a cell body and an axon. Dendrites receive information from receptors or other neurons. The cell body processes the signal, and the axon carries the nerve impulse away from the cell body. At the end of an axon, chemicals called neurotransmitters may be released into the synapse, the small gap between neurons. These chemicals stimulate the next neuron or an effector. This arrangement allows information to travel in a coordinated direction. Neurons therefore provide rapid communication between sensory organs, the central nervous system and muscles or glands This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1924 Marks 6. Control and Coordination Explain reflex action and distinguish it from a voluntary action Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A reflex action is a rapid, automatic response to a stimulus that generally occurs without conscious decision. For example, withdrawing the hand from a hot object is a reflex response. The pathway followed by the nerve impulse is called a reflex arc and usually involves a receptor, sensory neuron, relay neuron, motor neuron and effector. Reflex actions help protect the body by reducing response time. Voluntary actions, in contrast, are consciously controlled, such as writing or walking. Although the brain may receive information about a reflex, the immediate response is coordinated through the spinal cord in many common reflexes A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1934 Marks 6. Control and Coordination Explain plant hormones and their role in coordinating growth responses Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Plant hormones are chemical substances that regulate growth and development. Auxin promotes cell growth and is involved in phototropism. When light falls from one side, auxin distribution causes cells on the shaded side to elongate more, making the shoot bend toward light. Gibberellins promote stem growth and seed germination, while cytokinins encourage cell division. Abscisic acid generally inhibits growth and helps plants respond to stress. Ethylene promotes fruit ripening. Unlike animals, plants do not have a nervous system, so chemical coordination through hormones and directional growth responses allows them to respond to environmental conditions Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1944 Marks 6. Control and Coordination Compare nervous and hormonal coordination in humans Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Nervous coordination uses electrical impulses transmitted through neurons and generally produces rapid, short-lived responses. Hormonal coordination uses chemical messengers released by endocrine glands into the blood. Hormones usually act more slowly but their effects may last longer. For example, a reflex action is controlled rapidly through the nervous system, whereas growth and metabolic regulation involve hormones. The two systems work together to maintain coordination and internal balance. The nervous system is particularly useful for immediate responses to stimuli, while hormones regulate processes such as growth, reproduction, metabolism and long-term adaptation A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1954 Marks 6. Control and Coordination Explain the role of the brain, spinal cord and peripheral nerves in coordination Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The brain and spinal cord together form the central nervous system. The brain receives sensory information, interprets it and coordinates appropriate responses. Different regions of the brain perform different functions, including thinking, memory, balance and control of involuntary activities. The spinal cord connects the brain with peripheral nerves and also coordinates many reflex actions. Peripheral nerves carry sensory information toward the central nervous system and motor commands toward muscles or glands. This communication network allows the body to detect changes, process information and respond appropriately. Protection by the skull and vertebral column helps safeguard these important nervous structures For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1964 Marks 6. Control and Coordination Explain the structure of a neuron and describe how a nerve impulse is transmitted Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A neuron is the basic structural and functional unit of the nervous system. It has dendrites, a cell body and an axon. Dendrites receive information from receptors or other neurons. The cell body processes the signal, and the axon carries the nerve impulse away from the cell body. At the end of an axon, chemicals called neurotransmitters may be released into the synapse, the small gap between neurons. These chemicals stimulate the next neuron or an effector. This arrangement allows information to travel in a coordinated direction. Neurons therefore provide rapid communication between sensory organs, the central nervous system and muscles or glands This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1974 Marks 6. Control and Coordination Explain reflex action and distinguish it from a voluntary action Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A reflex action is a rapid, automatic response to a stimulus that generally occurs without conscious decision. For example, withdrawing the hand from a hot object is a reflex response. The pathway followed by the nerve impulse is called a reflex arc and usually involves a receptor, sensory neuron, relay neuron, motor neuron and effector. Reflex actions help protect the body by reducing response time. Voluntary actions, in contrast, are consciously controlled, such as writing or walking. Although the brain may receive information about a reflex, the immediate response is coordinated through the spinal cord in many common reflexes A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1984 Marks 6. Control and Coordination Explain plant hormones and their role in coordinating growth responses Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Plant hormones are chemical substances that regulate growth and development. Auxin promotes cell growth and is involved in phototropism. When light falls from one side, auxin distribution causes cells on the shaded side to elongate more, making the shoot bend toward light. Gibberellins promote stem growth and seed germination, while cytokinins encourage cell division. Abscisic acid generally inhibits growth and helps plants respond to stress. Ethylene promotes fruit ripening. Unlike animals, plants do not have a nervous system, so chemical coordination through hormones and directional growth responses allows them to respond to environmental conditions Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 1994 Marks 6. Control and Coordination Compare nervous and hormonal coordination in humans Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Nervous coordination uses electrical impulses transmitted through neurons and generally produces rapid, short-lived responses. Hormonal coordination uses chemical messengers released by endocrine glands into the blood. Hormones usually act more slowly but their effects may last longer. For example, a reflex action is controlled rapidly through the nervous system, whereas growth and metabolic regulation involve hormones. The two systems work together to maintain coordination and internal balance. The nervous system is particularly useful for immediate responses to stimuli, while hormones regulate processes such as growth, reproduction, metabolism and long-term adaptation A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2004 Marks 6. Control and Coordination Explain the role of the brain, spinal cord and peripheral nerves in coordination Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The brain and spinal cord together form the central nervous system. The brain receives sensory information, interprets it and coordinates appropriate responses. Different regions of the brain perform different functions, including thinking, memory, balance and control of involuntary activities. The spinal cord connects the brain with peripheral nerves and also coordinates many reflex actions. Peripheral nerves carry sensory information toward the central nervous system and motor commands toward muscles or glands. This communication network allows the body to detect changes, process information and respond appropriately. Protection by the skull and vertebral column helps safeguard these important nervous structures For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2014 Marks 6. Control and Coordination Explain the structure of a neuron and describe how a nerve impulse is transmitted Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A neuron is the basic structural and functional unit of the nervous system. It has dendrites, a cell body and an axon. Dendrites receive information from receptors or other neurons. The cell body processes the signal, and the axon carries the nerve impulse away from the cell body. At the end of an axon, chemicals called neurotransmitters may be released into the synapse, the small gap between neurons. These chemicals stimulate the next neuron or an effector. This arrangement allows information to travel in a coordinated direction. Neurons therefore provide rapid communication between sensory organs, the central nervous system and muscles or glands This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2024 Marks 6. Control and Coordination Explain reflex action and distinguish it from a voluntary action Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A reflex action is a rapid, automatic response to a stimulus that generally occurs without conscious decision. For example, withdrawing the hand from a hot object is a reflex response. The pathway followed by the nerve impulse is called a reflex arc and usually involves a receptor, sensory neuron, relay neuron, motor neuron and effector. Reflex actions help protect the body by reducing response time. Voluntary actions, in contrast, are consciously controlled, such as writing or walking. Although the brain may receive information about a reflex, the immediate response is coordinated through the spinal cord in many common reflexes A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2034 Marks 6. Control and Coordination Explain plant hormones and their role in coordinating growth responses Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Plant hormones are chemical substances that regulate growth and development. Auxin promotes cell growth and is involved in phototropism. When light falls from one side, auxin distribution causes cells on the shaded side to elongate more, making the shoot bend toward light. Gibberellins promote stem growth and seed germination, while cytokinins encourage cell division. Abscisic acid generally inhibits growth and helps plants respond to stress. Ethylene promotes fruit ripening. Unlike animals, plants do not have a nervous system, so chemical coordination through hormones and directional growth responses allows them to respond to environmental conditions Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2044 Marks 6. Control and Coordination Compare nervous and hormonal coordination in humans Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Nervous coordination uses electrical impulses transmitted through neurons and generally produces rapid, short-lived responses. Hormonal coordination uses chemical messengers released by endocrine glands into the blood. Hormones usually act more slowly but their effects may last longer. For example, a reflex action is controlled rapidly through the nervous system, whereas growth and metabolic regulation involve hormones. The two systems work together to maintain coordination and internal balance. The nervous system is particularly useful for immediate responses to stimuli, while hormones regulate processes such as growth, reproduction, metabolism and long-term adaptation A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2054 Marks 6. Control and Coordination Explain the role of the brain, spinal cord and peripheral nerves in coordination Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The brain and spinal cord together form the central nervous system. The brain receives sensory information, interprets it and coordinates appropriate responses. Different regions of the brain perform different functions, including thinking, memory, balance and control of involuntary activities. The spinal cord connects the brain with peripheral nerves and also coordinates many reflex actions. Peripheral nerves carry sensory information toward the central nervous system and motor commands toward muscles or glands. This communication network allows the body to detect changes, process information and respond appropriately. Protection by the skull and vertebral column helps safeguard these important nervous structures For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2064 Marks 6. Control and Coordination Explain the structure of a neuron and describe how a nerve impulse is transmitted Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A neuron is the basic structural and functional unit of the nervous system. It has dendrites, a cell body and an axon. Dendrites receive information from receptors or other neurons. The cell body processes the signal, and the axon carries the nerve impulse away from the cell body. At the end of an axon, chemicals called neurotransmitters may be released into the synapse, the small gap between neurons. These chemicals stimulate the next neuron or an effector. This arrangement allows information to travel in a coordinated direction. Neurons therefore provide rapid communication between sensory organs, the central nervous system and muscles or glands This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2074 Marks 6. Control and Coordination Explain reflex action and distinguish it from a voluntary action Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A reflex action is a rapid, automatic response to a stimulus that generally occurs without conscious decision. For example, withdrawing the hand from a hot object is a reflex response. The pathway followed by the nerve impulse is called a reflex arc and usually involves a receptor, sensory neuron, relay neuron, motor neuron and effector. Reflex actions help protect the body by reducing response time. Voluntary actions, in contrast, are consciously controlled, such as writing or walking. Although the brain may receive information about a reflex, the immediate response is coordinated through the spinal cord in many common reflexes A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2084 Marks 6. Control and Coordination Explain plant hormones and their role in coordinating growth responses Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Plant hormones are chemical substances that regulate growth and development. Auxin promotes cell growth and is involved in phototropism. When light falls from one side, auxin distribution causes cells on the shaded side to elongate more, making the shoot bend toward light. Gibberellins promote stem growth and seed germination, while cytokinins encourage cell division. Abscisic acid generally inhibits growth and helps plants respond to stress. Ethylene promotes fruit ripening. Unlike animals, plants do not have a nervous system, so chemical coordination through hormones and directional growth responses allows them to respond to environmental conditions Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2094 Marks 6. Control and Coordination Compare nervous and hormonal coordination in humans Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Nervous coordination uses electrical impulses transmitted through neurons and generally produces rapid, short-lived responses. Hormonal coordination uses chemical messengers released by endocrine glands into the blood. Hormones usually act more slowly but their effects may last longer. For example, a reflex action is controlled rapidly through the nervous system, whereas growth and metabolic regulation involve hormones. The two systems work together to maintain coordination and internal balance. The nervous system is particularly useful for immediate responses to stimuli, while hormones regulate processes such as growth, reproduction, metabolism and long-term adaptation A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2104 Marks 6. Control and Coordination Explain the role of the brain, spinal cord and peripheral nerves in coordination Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The brain and spinal cord together form the central nervous system. The brain receives sensory information, interprets it and coordinates appropriate responses. Different regions of the brain perform different functions, including thinking, memory, balance and control of involuntary activities. The spinal cord connects the brain with peripheral nerves and also coordinates many reflex actions. Peripheral nerves carry sensory information toward the central nervous system and motor commands toward muscles or glands. This communication network allows the body to detect changes, process information and respond appropriately. Protection by the skull and vertebral column helps safeguard these important nervous structures For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2114 Marks 6. Control and Coordination Explain the structure of a neuron and describe how a nerve impulse is transmitted Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A neuron is the basic structural and functional unit of the nervous system. It has dendrites, a cell body and an axon. Dendrites receive information from receptors or other neurons. The cell body processes the signal, and the axon carries the nerve impulse away from the cell body. At the end of an axon, chemicals called neurotransmitters may be released into the synapse, the small gap between neurons. These chemicals stimulate the next neuron or an effector. This arrangement allows information to travel in a coordinated direction. Neurons therefore provide rapid communication between sensory organs, the central nervous system and muscles or glands This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2124 Marks 6. Control and Coordination Explain reflex action and distinguish it from a voluntary action Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A reflex action is a rapid, automatic response to a stimulus that generally occurs without conscious decision. For example, withdrawing the hand from a hot object is a reflex response. The pathway followed by the nerve impulse is called a reflex arc and usually involves a receptor, sensory neuron, relay neuron, motor neuron and effector. Reflex actions help protect the body by reducing response time. Voluntary actions, in contrast, are consciously controlled, such as writing or walking. Although the brain may receive information about a reflex, the immediate response is coordinated through the spinal cord in many common reflexes A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2134 Marks 6. Control and Coordination Explain plant hormones and their role in coordinating growth responses Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Plant hormones are chemical substances that regulate growth and development. Auxin promotes cell growth and is involved in phototropism. When light falls from one side, auxin distribution causes cells on the shaded side to elongate more, making the shoot bend toward light. Gibberellins promote stem growth and seed germination, while cytokinins encourage cell division. Abscisic acid generally inhibits growth and helps plants respond to stress. Ethylene promotes fruit ripening. Unlike animals, plants do not have a nervous system, so chemical coordination through hormones and directional growth responses allows them to respond to environmental conditions Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2144 Marks 6. Control and Coordination Compare nervous and hormonal coordination in humans Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Nervous coordination uses electrical impulses transmitted through neurons and generally produces rapid, short-lived responses. Hormonal coordination uses chemical messengers released by endocrine glands into the blood. Hormones usually act more slowly but their effects may last longer. For example, a reflex action is controlled rapidly through the nervous system, whereas growth and metabolic regulation involve hormones. The two systems work together to maintain coordination and internal balance. The nervous system is particularly useful for immediate responses to stimuli, while hormones regulate processes such as growth, reproduction, metabolism and long-term adaptation A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2154 Marks 6. Control and Coordination Explain the role of the brain, spinal cord and peripheral nerves in coordination Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
The brain and spinal cord together form the central nervous system. The brain receives sensory information, interprets it and coordinates appropriate responses. Different regions of the brain perform different functions, including thinking, memory, balance and control of involuntary activities. The spinal cord connects the brain with peripheral nerves and also coordinates many reflex actions. Peripheral nerves carry sensory information toward the central nervous system and motor commands toward muscles or glands. This communication network allows the body to detect changes, process information and respond appropriately. Protection by the skull and vertebral column helps safeguard these important nervous structures For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2164 Marks 6. Control and Coordination Explain the structure of a neuron and describe how a nerve impulse is transmitted Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A neuron is the basic structural and functional unit of the nervous system. It has dendrites, a cell body and an axon. Dendrites receive information from receptors or other neurons. The cell body processes the signal, and the axon carries the nerve impulse away from the cell body. At the end of an axon, chemicals called neurotransmitters may be released into the synapse, the small gap between neurons. These chemicals stimulate the next neuron or an effector. This arrangement allows information to travel in a coordinated direction. Neurons therefore provide rapid communication between sensory organs, the central nervous system and muscles or glands This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2174 Marks 7. How do Organisms Reproduce? Compare asexual and sexual reproduction and explain their biological significance. Click to View Answer ▼
Answer:
Asexual reproduction generally involves a single parent and does not require fusion of gametes. It can occur by methods such as binary fission, budding, fragmentation, spore formation and vegetative propagation. It is usually rapid and produces offspring genetically similar to the parent. Sexual reproduction involves formation of male and female gametes and their fusion, usually producing greater genetic variation. Asexual reproduction is advantageous when conditions are stable and rapid multiplication is useful. Sexual reproduction is important for generating variations that can improve the ability of populations to survive environmental changes. Thus, both forms contribute differently to continuity of species.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2184 Marks 7. How do Organisms Reproduce? Explain reproduction in flowering plants from pollination to seed formation. Click to View Answer ▼
Answer:
Sexual reproduction in flowering plants begins with transfer of pollen grains from anther to stigma, called pollination. The pollen grain germinates on a suitable stigma and forms a pollen tube that grows through the style toward the ovule. Male gametes travel through the pollen tube and one fuses with the egg to form a zygote. This is fertilisation. The zygote develops into an embryo, while the ovule develops into a seed and the ovary generally develops into a fruit. The seed contains the embryo and stored food needed for early growth. This process ensures formation of new plants and contributes to variation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2194 Marks 7. How do Organisms Reproduce? Explain human male and female reproductive systems and their major functions. Click to View Answer ▼
Answer:
The male reproductive system includes testes, sperm ducts and glands. Testes produce sperm and the male hormone testosterone. Sperm travel through ducts and mix with glandular secretions to form semen. The female reproductive system includes ovaries, oviducts, uterus and vagina. Ovaries produce ova and female hormones. The oviduct is the usual site of fertilisation, while the uterus provides a suitable environment for development of the embryo. If fertilisation does not occur, the uterine lining is shed during menstruation. These organs work together to produce gametes, allow fertilisation and support development of the embryo during reproduction.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2204 Marks 7. How do Organisms Reproduce? Explain the importance of reproductive health and discuss major methods of contraception. Click to View Answer ▼
Answer:
Reproductive health involves physical and social well-being related to reproduction. Contraception helps prevent unwanted pregnancy and may also help in family planning. Barrier methods such as condoms prevent sperm from reaching the egg and also reduce the risk of many sexually transmitted infections. Hormonal methods such as oral contraceptive pills prevent ovulation or alter reproductive conditions. Intrauterine devices can prevent fertilisation or implantation. Surgical methods permanently block the reproductive ducts. The choice of method should be informed and medically appropriate. Reproductive health also includes hygiene, awareness, responsible decision-making and prevention of sexually transmitted infections.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2214 Marks 7. How do Organisms Reproduce? Explain how variations arise during reproduction and why they are important for evolution. Click to View Answer ▼
Answer:
Variations are differences among individuals of the same species. During sexual reproduction, genetic material from two parents is combined, producing new combinations of traits. Variations can also arise due to changes in DNA. Environmental factors may influence the expression of some characteristics, although such changes are not necessarily inherited. Variations are important because they provide differences on which natural selection can act. If environmental conditions change, some variations may give individuals a survival or reproductive advantage. Over many generations, advantageous inherited variations can become more common in a population, contributing to evolutionary change.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2224 Marks 7. How do Organisms Reproduce? Compare asexual and sexual reproduction and explain their biological significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Asexual reproduction generally involves a single parent and does not require fusion of gametes. It can occur by methods such as binary fission, budding, fragmentation, spore formation and vegetative propagation. It is usually rapid and produces offspring genetically similar to the parent. Sexual reproduction involves formation of male and female gametes and their fusion, usually producing greater genetic variation. Asexual reproduction is advantageous when conditions are stable and rapid multiplication is useful. Sexual reproduction is important for generating variations that can improve the ability of populations to survive environmental changes. Thus, both forms contribute differently to continuity of species This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2234 Marks 7. How do Organisms Reproduce? Explain reproduction in flowering plants from pollination to seed formation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Sexual reproduction in flowering plants begins with transfer of pollen grains from anther to stigma, called pollination. The pollen grain germinates on a suitable stigma and forms a pollen tube that grows through the style toward the ovule. Male gametes travel through the pollen tube and one fuses with the egg to form a zygote. This is fertilisation. The zygote develops into an embryo, while the ovule develops into a seed and the ovary generally develops into a fruit. The seed contains the embryo and stored food needed for early growth. This process ensures formation of new plants and contributes to variation A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2244 Marks 7. How do Organisms Reproduce? Explain human male and female reproductive systems and their major functions Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The male reproductive system includes testes, sperm ducts and glands. Testes produce sperm and the male hormone testosterone. Sperm travel through ducts and mix with glandular secretions to form semen. The female reproductive system includes ovaries, oviducts, uterus and vagina. Ovaries produce ova and female hormones. The oviduct is the usual site of fertilisation, while the uterus provides a suitable environment for development of the embryo. If fertilisation does not occur, the uterine lining is shed during menstruation. These organs work together to produce gametes, allow fertilisation and support development of the embryo during reproduction Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2254 Marks 7. How do Organisms Reproduce? Explain the importance of reproductive health and discuss major methods of contraception Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Reproductive health involves physical and social well-being related to reproduction. Contraception helps prevent unwanted pregnancy and may also help in family planning. Barrier methods such as condoms prevent sperm from reaching the egg and also reduce the risk of many sexually transmitted infections. Hormonal methods such as oral contraceptive pills prevent ovulation or alter reproductive conditions. Intrauterine devices can prevent fertilisation or implantation. Surgical methods permanently block the reproductive ducts. The choice of method should be informed and medically appropriate. Reproductive health also includes hygiene, awareness, responsible decision-making and prevention of sexually transmitted infections A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2264 Marks 7. How do Organisms Reproduce? Explain how variations arise during reproduction and why they are important for evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variations are differences among individuals of the same species. During sexual reproduction, genetic material from two parents is combined, producing new combinations of traits. Variations can also arise due to changes in DNA. Environmental factors may influence the expression of some characteristics, although such changes are not necessarily inherited. Variations are important because they provide differences on which natural selection can act. If environmental conditions change, some variations may give individuals a survival or reproductive advantage. Over many generations, advantageous inherited variations can become more common in a population, contributing to evolutionary change For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2274 Marks 7. How do Organisms Reproduce? Compare asexual and sexual reproduction and explain their biological significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Asexual reproduction generally involves a single parent and does not require fusion of gametes. It can occur by methods such as binary fission, budding, fragmentation, spore formation and vegetative propagation. It is usually rapid and produces offspring genetically similar to the parent. Sexual reproduction involves formation of male and female gametes and their fusion, usually producing greater genetic variation. Asexual reproduction is advantageous when conditions are stable and rapid multiplication is useful. Sexual reproduction is important for generating variations that can improve the ability of populations to survive environmental changes. Thus, both forms contribute differently to continuity of species This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2284 Marks 7. How do Organisms Reproduce? Explain reproduction in flowering plants from pollination to seed formation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Sexual reproduction in flowering plants begins with transfer of pollen grains from anther to stigma, called pollination. The pollen grain germinates on a suitable stigma and forms a pollen tube that grows through the style toward the ovule. Male gametes travel through the pollen tube and one fuses with the egg to form a zygote. This is fertilisation. The zygote develops into an embryo, while the ovule develops into a seed and the ovary generally develops into a fruit. The seed contains the embryo and stored food needed for early growth. This process ensures formation of new plants and contributes to variation A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2294 Marks 7. How do Organisms Reproduce? Explain human male and female reproductive systems and their major functions Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The male reproductive system includes testes, sperm ducts and glands. Testes produce sperm and the male hormone testosterone. Sperm travel through ducts and mix with glandular secretions to form semen. The female reproductive system includes ovaries, oviducts, uterus and vagina. Ovaries produce ova and female hormones. The oviduct is the usual site of fertilisation, while the uterus provides a suitable environment for development of the embryo. If fertilisation does not occur, the uterine lining is shed during menstruation. These organs work together to produce gametes, allow fertilisation and support development of the embryo during reproduction Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2304 Marks 7. How do Organisms Reproduce? Explain the importance of reproductive health and discuss major methods of contraception Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Reproductive health involves physical and social well-being related to reproduction. Contraception helps prevent unwanted pregnancy and may also help in family planning. Barrier methods such as condoms prevent sperm from reaching the egg and also reduce the risk of many sexually transmitted infections. Hormonal methods such as oral contraceptive pills prevent ovulation or alter reproductive conditions. Intrauterine devices can prevent fertilisation or implantation. Surgical methods permanently block the reproductive ducts. The choice of method should be informed and medically appropriate. Reproductive health also includes hygiene, awareness, responsible decision-making and prevention of sexually transmitted infections A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2314 Marks 7. How do Organisms Reproduce? Explain how variations arise during reproduction and why they are important for evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variations are differences among individuals of the same species. During sexual reproduction, genetic material from two parents is combined, producing new combinations of traits. Variations can also arise due to changes in DNA. Environmental factors may influence the expression of some characteristics, although such changes are not necessarily inherited. Variations are important because they provide differences on which natural selection can act. If environmental conditions change, some variations may give individuals a survival or reproductive advantage. Over many generations, advantageous inherited variations can become more common in a population, contributing to evolutionary change For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2324 Marks 7. How do Organisms Reproduce? Compare asexual and sexual reproduction and explain their biological significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Asexual reproduction generally involves a single parent and does not require fusion of gametes. It can occur by methods such as binary fission, budding, fragmentation, spore formation and vegetative propagation. It is usually rapid and produces offspring genetically similar to the parent. Sexual reproduction involves formation of male and female gametes and their fusion, usually producing greater genetic variation. Asexual reproduction is advantageous when conditions are stable and rapid multiplication is useful. Sexual reproduction is important for generating variations that can improve the ability of populations to survive environmental changes. Thus, both forms contribute differently to continuity of species This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2334 Marks 7. How do Organisms Reproduce? Explain reproduction in flowering plants from pollination to seed formation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Sexual reproduction in flowering plants begins with transfer of pollen grains from anther to stigma, called pollination. The pollen grain germinates on a suitable stigma and forms a pollen tube that grows through the style toward the ovule. Male gametes travel through the pollen tube and one fuses with the egg to form a zygote. This is fertilisation. The zygote develops into an embryo, while the ovule develops into a seed and the ovary generally develops into a fruit. The seed contains the embryo and stored food needed for early growth. This process ensures formation of new plants and contributes to variation A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2344 Marks 7. How do Organisms Reproduce? Explain human male and female reproductive systems and their major functions Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The male reproductive system includes testes, sperm ducts and glands. Testes produce sperm and the male hormone testosterone. Sperm travel through ducts and mix with glandular secretions to form semen. The female reproductive system includes ovaries, oviducts, uterus and vagina. Ovaries produce ova and female hormones. The oviduct is the usual site of fertilisation, while the uterus provides a suitable environment for development of the embryo. If fertilisation does not occur, the uterine lining is shed during menstruation. These organs work together to produce gametes, allow fertilisation and support development of the embryo during reproduction Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2354 Marks 7. How do Organisms Reproduce? Explain the importance of reproductive health and discuss major methods of contraception Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Reproductive health involves physical and social well-being related to reproduction. Contraception helps prevent unwanted pregnancy and may also help in family planning. Barrier methods such as condoms prevent sperm from reaching the egg and also reduce the risk of many sexually transmitted infections. Hormonal methods such as oral contraceptive pills prevent ovulation or alter reproductive conditions. Intrauterine devices can prevent fertilisation or implantation. Surgical methods permanently block the reproductive ducts. The choice of method should be informed and medically appropriate. Reproductive health also includes hygiene, awareness, responsible decision-making and prevention of sexually transmitted infections A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2364 Marks 7. How do Organisms Reproduce? Explain how variations arise during reproduction and why they are important for evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variations are differences among individuals of the same species. During sexual reproduction, genetic material from two parents is combined, producing new combinations of traits. Variations can also arise due to changes in DNA. Environmental factors may influence the expression of some characteristics, although such changes are not necessarily inherited. Variations are important because they provide differences on which natural selection can act. If environmental conditions change, some variations may give individuals a survival or reproductive advantage. Over many generations, advantageous inherited variations can become more common in a population, contributing to evolutionary change For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2374 Marks 7. How do Organisms Reproduce? Compare asexual and sexual reproduction and explain their biological significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Asexual reproduction generally involves a single parent and does not require fusion of gametes. It can occur by methods such as binary fission, budding, fragmentation, spore formation and vegetative propagation. It is usually rapid and produces offspring genetically similar to the parent. Sexual reproduction involves formation of male and female gametes and their fusion, usually producing greater genetic variation. Asexual reproduction is advantageous when conditions are stable and rapid multiplication is useful. Sexual reproduction is important for generating variations that can improve the ability of populations to survive environmental changes. Thus, both forms contribute differently to continuity of species This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2384 Marks 7. How do Organisms Reproduce? Explain reproduction in flowering plants from pollination to seed formation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Sexual reproduction in flowering plants begins with transfer of pollen grains from anther to stigma, called pollination. The pollen grain germinates on a suitable stigma and forms a pollen tube that grows through the style toward the ovule. Male gametes travel through the pollen tube and one fuses with the egg to form a zygote. This is fertilisation. The zygote develops into an embryo, while the ovule develops into a seed and the ovary generally develops into a fruit. The seed contains the embryo and stored food needed for early growth. This process ensures formation of new plants and contributes to variation A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2394 Marks 7. How do Organisms Reproduce? Explain human male and female reproductive systems and their major functions Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The male reproductive system includes testes, sperm ducts and glands. Testes produce sperm and the male hormone testosterone. Sperm travel through ducts and mix with glandular secretions to form semen. The female reproductive system includes ovaries, oviducts, uterus and vagina. Ovaries produce ova and female hormones. The oviduct is the usual site of fertilisation, while the uterus provides a suitable environment for development of the embryo. If fertilisation does not occur, the uterine lining is shed during menstruation. These organs work together to produce gametes, allow fertilisation and support development of the embryo during reproduction Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2404 Marks 7. How do Organisms Reproduce? Explain the importance of reproductive health and discuss major methods of contraception Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Reproductive health involves physical and social well-being related to reproduction. Contraception helps prevent unwanted pregnancy and may also help in family planning. Barrier methods such as condoms prevent sperm from reaching the egg and also reduce the risk of many sexually transmitted infections. Hormonal methods such as oral contraceptive pills prevent ovulation or alter reproductive conditions. Intrauterine devices can prevent fertilisation or implantation. Surgical methods permanently block the reproductive ducts. The choice of method should be informed and medically appropriate. Reproductive health also includes hygiene, awareness, responsible decision-making and prevention of sexually transmitted infections A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2414 Marks 7. How do Organisms Reproduce? Explain how variations arise during reproduction and why they are important for evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variations are differences among individuals of the same species. During sexual reproduction, genetic material from two parents is combined, producing new combinations of traits. Variations can also arise due to changes in DNA. Environmental factors may influence the expression of some characteristics, although such changes are not necessarily inherited. Variations are important because they provide differences on which natural selection can act. If environmental conditions change, some variations may give individuals a survival or reproductive advantage. Over many generations, advantageous inherited variations can become more common in a population, contributing to evolutionary change For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2424 Marks 7. How do Organisms Reproduce? Compare asexual and sexual reproduction and explain their biological significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Asexual reproduction generally involves a single parent and does not require fusion of gametes. It can occur by methods such as binary fission, budding, fragmentation, spore formation and vegetative propagation. It is usually rapid and produces offspring genetically similar to the parent. Sexual reproduction involves formation of male and female gametes and their fusion, usually producing greater genetic variation. Asexual reproduction is advantageous when conditions are stable and rapid multiplication is useful. Sexual reproduction is important for generating variations that can improve the ability of populations to survive environmental changes. Thus, both forms contribute differently to continuity of species This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2434 Marks 7. How do Organisms Reproduce? Explain reproduction in flowering plants from pollination to seed formation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Sexual reproduction in flowering plants begins with transfer of pollen grains from anther to stigma, called pollination. The pollen grain germinates on a suitable stigma and forms a pollen tube that grows through the style toward the ovule. Male gametes travel through the pollen tube and one fuses with the egg to form a zygote. This is fertilisation. The zygote develops into an embryo, while the ovule develops into a seed and the ovary generally develops into a fruit. The seed contains the embryo and stored food needed for early growth. This process ensures formation of new plants and contributes to variation A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2444 Marks 7. How do Organisms Reproduce? Explain human male and female reproductive systems and their major functions Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The male reproductive system includes testes, sperm ducts and glands. Testes produce sperm and the male hormone testosterone. Sperm travel through ducts and mix with glandular secretions to form semen. The female reproductive system includes ovaries, oviducts, uterus and vagina. Ovaries produce ova and female hormones. The oviduct is the usual site of fertilisation, while the uterus provides a suitable environment for development of the embryo. If fertilisation does not occur, the uterine lining is shed during menstruation. These organs work together to produce gametes, allow fertilisation and support development of the embryo during reproduction Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2454 Marks 7. How do Organisms Reproduce? Explain the importance of reproductive health and discuss major methods of contraception Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Reproductive health involves physical and social well-being related to reproduction. Contraception helps prevent unwanted pregnancy and may also help in family planning. Barrier methods such as condoms prevent sperm from reaching the egg and also reduce the risk of many sexually transmitted infections. Hormonal methods such as oral contraceptive pills prevent ovulation or alter reproductive conditions. Intrauterine devices can prevent fertilisation or implantation. Surgical methods permanently block the reproductive ducts. The choice of method should be informed and medically appropriate. Reproductive health also includes hygiene, awareness, responsible decision-making and prevention of sexually transmitted infections A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2464 Marks 7. How do Organisms Reproduce? Explain how variations arise during reproduction and why they are important for evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variations are differences among individuals of the same species. During sexual reproduction, genetic material from two parents is combined, producing new combinations of traits. Variations can also arise due to changes in DNA. Environmental factors may influence the expression of some characteristics, although such changes are not necessarily inherited. Variations are important because they provide differences on which natural selection can act. If environmental conditions change, some variations may give individuals a survival or reproductive advantage. Over many generations, advantageous inherited variations can become more common in a population, contributing to evolutionary change For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2474 Marks 7. How do Organisms Reproduce? Compare asexual and sexual reproduction and explain their biological significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Asexual reproduction generally involves a single parent and does not require fusion of gametes. It can occur by methods such as binary fission, budding, fragmentation, spore formation and vegetative propagation. It is usually rapid and produces offspring genetically similar to the parent. Sexual reproduction involves formation of male and female gametes and their fusion, usually producing greater genetic variation. Asexual reproduction is advantageous when conditions are stable and rapid multiplication is useful. Sexual reproduction is important for generating variations that can improve the ability of populations to survive environmental changes. Thus, both forms contribute differently to continuity of species This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2484 Marks 7. How do Organisms Reproduce? Explain reproduction in flowering plants from pollination to seed formation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Sexual reproduction in flowering plants begins with transfer of pollen grains from anther to stigma, called pollination. The pollen grain germinates on a suitable stigma and forms a pollen tube that grows through the style toward the ovule. Male gametes travel through the pollen tube and one fuses with the egg to form a zygote. This is fertilisation. The zygote develops into an embryo, while the ovule develops into a seed and the ovary generally develops into a fruit. The seed contains the embryo and stored food needed for early growth. This process ensures formation of new plants and contributes to variation A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2494 Marks 7. How do Organisms Reproduce? Explain human male and female reproductive systems and their major functions Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
The male reproductive system includes testes, sperm ducts and glands. Testes produce sperm and the male hormone testosterone. Sperm travel through ducts and mix with glandular secretions to form semen. The female reproductive system includes ovaries, oviducts, uterus and vagina. Ovaries produce ova and female hormones. The oviduct is the usual site of fertilisation, while the uterus provides a suitable environment for development of the embryo. If fertilisation does not occur, the uterine lining is shed during menstruation. These organs work together to produce gametes, allow fertilisation and support development of the embryo during reproduction Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2504 Marks 7. How do Organisms Reproduce? Explain the importance of reproductive health and discuss major methods of contraception Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Reproductive health involves physical and social well-being related to reproduction. Contraception helps prevent unwanted pregnancy and may also help in family planning. Barrier methods such as condoms prevent sperm from reaching the egg and also reduce the risk of many sexually transmitted infections. Hormonal methods such as oral contraceptive pills prevent ovulation or alter reproductive conditions. Intrauterine devices can prevent fertilisation or implantation. Surgical methods permanently block the reproductive ducts. The choice of method should be informed and medically appropriate. Reproductive health also includes hygiene, awareness, responsible decision-making and prevention of sexually transmitted infections A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2514 Marks 7. How do Organisms Reproduce? Explain how variations arise during reproduction and why they are important for evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variations are differences among individuals of the same species. During sexual reproduction, genetic material from two parents is combined, producing new combinations of traits. Variations can also arise due to changes in DNA. Environmental factors may influence the expression of some characteristics, although such changes are not necessarily inherited. Variations are important because they provide differences on which natural selection can act. If environmental conditions change, some variations may give individuals a survival or reproductive advantage. Over many generations, advantageous inherited variations can become more common in a population, contributing to evolutionary change For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2524 Marks 7. How do Organisms Reproduce? Compare asexual and sexual reproduction and explain their biological significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Asexual reproduction generally involves a single parent and does not require fusion of gametes. It can occur by methods such as binary fission, budding, fragmentation, spore formation and vegetative propagation. It is usually rapid and produces offspring genetically similar to the parent. Sexual reproduction involves formation of male and female gametes and their fusion, usually producing greater genetic variation. Asexual reproduction is advantageous when conditions are stable and rapid multiplication is useful. Sexual reproduction is important for generating variations that can improve the ability of populations to survive environmental changes. Thus, both forms contribute differently to continuity of species This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2534 Marks 8. Heredity Explain Mendel's monohybrid cross and derive the phenotypic ratio obtained. Click to View Answer ▼
Answer:
Mendel studied inheritance using pea plants and considered contrasting traits. Suppose tallness is dominant over dwarfness. A pure tall plant with genotype TT is crossed with a pure dwarf plant tt. All F1 offspring receive T from one parent and t from the other, so their genotype is Tt and phenotype is tall. When F1 plants are crossed, Tt × Tt produces TT, Tt, Tt and tt. Thus, the genotypic ratio is 1:2:1, while the phenotypic ratio is 3 tall : 1 dwarf. The result demonstrates segregation of alleles and the dominance of one allele over another.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2544 Marks 8. Heredity Differentiate genotype and phenotype and explain how genes influence characteristics. Click to View Answer ▼
Answer:
Genotype refers to the genetic constitution of an organism for a particular trait, whereas phenotype refers to the observable expression of that trait. For example, in pea plants, TT and Tt may both produce a tall phenotype if T is dominant, while tt produces a dwarf phenotype. Genes influence characteristics by carrying information that controls the production of proteins or functional molecules. These products influence biological processes and visible traits. However, phenotype can also be influenced by environmental conditions. Therefore, genotype provides the genetic potential, while phenotype represents the resulting observable characteristic.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2554 Marks 8. Heredity Explain sex determination in humans using the role of X and Y chromosomes. Click to View Answer ▼
Answer:
In humans, females generally have XX sex chromosomes and males have XY. The egg produced by a female carries only an X chromosome. A male produces two types of sperm: some carry X and others carry Y. If an X-carrying sperm fertilises the egg, the zygote becomes XX and typically develops as female. If a Y-carrying sperm fertilises the egg, the zygote becomes XY and typically develops as male. Therefore, the type of sperm involved in fertilisation determines the chromosomal sex of the child. This also explains why the father contributes either an X or a Y chromosome.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2564 Marks 8. Heredity Explain acquired and inherited traits and discuss their significance in heredity. Click to View Answer ▼
Answer:
Inherited traits are characteristics transmitted genetically from parents to offspring through genes. Examples include blood group and certain genetic features. Acquired traits develop during an individual's lifetime due to environmental influences, learning or changes in body tissues and are generally not transmitted genetically to offspring. For example, increased muscle strength from training is an acquired characteristic. Heredity mainly concerns transmission of genetic information from one generation to the next. Variations in inherited traits provide the raw material for natural selection, while acquired changes generally do not contribute directly to genetic evolution unless they involve heritable genetic changes.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2574 Marks 8. Heredity Explain how variations and natural selection can contribute to evolution. Click to View Answer ▼
Answer:
Variation means differences among individuals of a population. Some variations are inherited and may arise from genetic recombination or changes in DNA. When environmental conditions change, individuals possessing certain advantageous inherited variations may have better chances of survival and reproduction. Their favourable traits can therefore become more common in later generations. This process is called natural selection. Over very long periods, accumulation of inherited differences can produce major changes in populations and may contribute to formation of new species. Thus, evolution is closely connected with heritable variation and differential survival and reproduction.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2584 Marks 8. Heredity Explain Mendel's monohybrid cross and derive the phenotypic ratio obtained Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Mendel studied inheritance using pea plants and considered contrasting traits. Suppose tallness is dominant over dwarfness. A pure tall plant with genotype TT is crossed with a pure dwarf plant tt. All F1 offspring receive T from one parent and t from the other, so their genotype is Tt and phenotype is tall. When F1 plants are crossed, Tt × Tt produces TT, Tt, Tt and tt. Thus, the genotypic ratio is 1:2:1, while the phenotypic ratio is 3 tall : 1 dwarf. The result demonstrates segregation of alleles and the dominance of one allele over another This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2594 Marks 8. Heredity Differentiate genotype and phenotype and explain how genes influence characteristics Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Genotype refers to the genetic constitution of an organism for a particular trait, whereas phenotype refers to the observable expression of that trait. For example, in pea plants, TT and Tt may both produce a tall phenotype if T is dominant, while tt produces a dwarf phenotype. Genes influence characteristics by carrying information that controls the production of proteins or functional molecules. These products influence biological processes and visible traits. However, phenotype can also be influenced by environmental conditions. Therefore, genotype provides the genetic potential, while phenotype represents the resulting observable characteristic A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2604 Marks 8. Heredity Explain sex determination in humans using the role of X and Y chromosomes Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
In humans, females generally have XX sex chromosomes and males have XY. The egg produced by a female carries only an X chromosome. A male produces two types of sperm: some carry X and others carry Y. If an X-carrying sperm fertilises the egg, the zygote becomes XX and typically develops as female. If a Y-carrying sperm fertilises the egg, the zygote becomes XY and typically develops as male. Therefore, the type of sperm involved in fertilisation determines the chromosomal sex of the child. This also explains why the father contributes either an X or a Y chromosome Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2614 Marks 8. Heredity Explain acquired and inherited traits and discuss their significance in heredity Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Inherited traits are characteristics transmitted genetically from parents to offspring through genes. Examples include blood group and certain genetic features. Acquired traits develop during an individual's lifetime due to environmental influences, learning or changes in body tissues and are generally not transmitted genetically to offspring. For example, increased muscle strength from training is an acquired characteristic. Heredity mainly concerns transmission of genetic information from one generation to the next. Variations in inherited traits provide the raw material for natural selection, while acquired changes generally do not contribute directly to genetic evolution unless they involve heritable genetic changes A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2624 Marks 8. Heredity Explain how variations and natural selection can contribute to evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variation means differences among individuals of a population. Some variations are inherited and may arise from genetic recombination or changes in DNA. When environmental conditions change, individuals possessing certain advantageous inherited variations may have better chances of survival and reproduction. Their favourable traits can therefore become more common in later generations. This process is called natural selection. Over very long periods, accumulation of inherited differences can produce major changes in populations and may contribute to formation of new species. Thus, evolution is closely connected with heritable variation and differential survival and reproduction For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2634 Marks 8. Heredity Explain Mendel's monohybrid cross and derive the phenotypic ratio obtained Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Mendel studied inheritance using pea plants and considered contrasting traits. Suppose tallness is dominant over dwarfness. A pure tall plant with genotype TT is crossed with a pure dwarf plant tt. All F1 offspring receive T from one parent and t from the other, so their genotype is Tt and phenotype is tall. When F1 plants are crossed, Tt × Tt produces TT, Tt, Tt and tt. Thus, the genotypic ratio is 1:2:1, while the phenotypic ratio is 3 tall : 1 dwarf. The result demonstrates segregation of alleles and the dominance of one allele over another This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2644 Marks 8. Heredity Differentiate genotype and phenotype and explain how genes influence characteristics Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Genotype refers to the genetic constitution of an organism for a particular trait, whereas phenotype refers to the observable expression of that trait. For example, in pea plants, TT and Tt may both produce a tall phenotype if T is dominant, while tt produces a dwarf phenotype. Genes influence characteristics by carrying information that controls the production of proteins or functional molecules. These products influence biological processes and visible traits. However, phenotype can also be influenced by environmental conditions. Therefore, genotype provides the genetic potential, while phenotype represents the resulting observable characteristic A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2654 Marks 8. Heredity Explain sex determination in humans using the role of X and Y chromosomes Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
In humans, females generally have XX sex chromosomes and males have XY. The egg produced by a female carries only an X chromosome. A male produces two types of sperm: some carry X and others carry Y. If an X-carrying sperm fertilises the egg, the zygote becomes XX and typically develops as female. If a Y-carrying sperm fertilises the egg, the zygote becomes XY and typically develops as male. Therefore, the type of sperm involved in fertilisation determines the chromosomal sex of the child. This also explains why the father contributes either an X or a Y chromosome Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2664 Marks 8. Heredity Explain acquired and inherited traits and discuss their significance in heredity Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Inherited traits are characteristics transmitted genetically from parents to offspring through genes. Examples include blood group and certain genetic features. Acquired traits develop during an individual's lifetime due to environmental influences, learning or changes in body tissues and are generally not transmitted genetically to offspring. For example, increased muscle strength from training is an acquired characteristic. Heredity mainly concerns transmission of genetic information from one generation to the next. Variations in inherited traits provide the raw material for natural selection, while acquired changes generally do not contribute directly to genetic evolution unless they involve heritable genetic changes A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2674 Marks 8. Heredity Explain how variations and natural selection can contribute to evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variation means differences among individuals of a population. Some variations are inherited and may arise from genetic recombination or changes in DNA. When environmental conditions change, individuals possessing certain advantageous inherited variations may have better chances of survival and reproduction. Their favourable traits can therefore become more common in later generations. This process is called natural selection. Over very long periods, accumulation of inherited differences can produce major changes in populations and may contribute to formation of new species. Thus, evolution is closely connected with heritable variation and differential survival and reproduction For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2684 Marks 8. Heredity Explain Mendel's monohybrid cross and derive the phenotypic ratio obtained Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Mendel studied inheritance using pea plants and considered contrasting traits. Suppose tallness is dominant over dwarfness. A pure tall plant with genotype TT is crossed with a pure dwarf plant tt. All F1 offspring receive T from one parent and t from the other, so their genotype is Tt and phenotype is tall. When F1 plants are crossed, Tt × Tt produces TT, Tt, Tt and tt. Thus, the genotypic ratio is 1:2:1, while the phenotypic ratio is 3 tall : 1 dwarf. The result demonstrates segregation of alleles and the dominance of one allele over another This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2694 Marks 8. Heredity Differentiate genotype and phenotype and explain how genes influence characteristics Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Genotype refers to the genetic constitution of an organism for a particular trait, whereas phenotype refers to the observable expression of that trait. For example, in pea plants, TT and Tt may both produce a tall phenotype if T is dominant, while tt produces a dwarf phenotype. Genes influence characteristics by carrying information that controls the production of proteins or functional molecules. These products influence biological processes and visible traits. However, phenotype can also be influenced by environmental conditions. Therefore, genotype provides the genetic potential, while phenotype represents the resulting observable characteristic A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2704 Marks 8. Heredity Explain sex determination in humans using the role of X and Y chromosomes Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
In humans, females generally have XX sex chromosomes and males have XY. The egg produced by a female carries only an X chromosome. A male produces two types of sperm: some carry X and others carry Y. If an X-carrying sperm fertilises the egg, the zygote becomes XX and typically develops as female. If a Y-carrying sperm fertilises the egg, the zygote becomes XY and typically develops as male. Therefore, the type of sperm involved in fertilisation determines the chromosomal sex of the child. This also explains why the father contributes either an X or a Y chromosome Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2714 Marks 8. Heredity Explain acquired and inherited traits and discuss their significance in heredity Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Inherited traits are characteristics transmitted genetically from parents to offspring through genes. Examples include blood group and certain genetic features. Acquired traits develop during an individual's lifetime due to environmental influences, learning or changes in body tissues and are generally not transmitted genetically to offspring. For example, increased muscle strength from training is an acquired characteristic. Heredity mainly concerns transmission of genetic information from one generation to the next. Variations in inherited traits provide the raw material for natural selection, while acquired changes generally do not contribute directly to genetic evolution unless they involve heritable genetic changes A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2724 Marks 8. Heredity Explain how variations and natural selection can contribute to evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variation means differences among individuals of a population. Some variations are inherited and may arise from genetic recombination or changes in DNA. When environmental conditions change, individuals possessing certain advantageous inherited variations may have better chances of survival and reproduction. Their favourable traits can therefore become more common in later generations. This process is called natural selection. Over very long periods, accumulation of inherited differences can produce major changes in populations and may contribute to formation of new species. Thus, evolution is closely connected with heritable variation and differential survival and reproduction For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2734 Marks 8. Heredity Explain Mendel's monohybrid cross and derive the phenotypic ratio obtained Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Mendel studied inheritance using pea plants and considered contrasting traits. Suppose tallness is dominant over dwarfness. A pure tall plant with genotype TT is crossed with a pure dwarf plant tt. All F1 offspring receive T from one parent and t from the other, so their genotype is Tt and phenotype is tall. When F1 plants are crossed, Tt × Tt produces TT, Tt, Tt and tt. Thus, the genotypic ratio is 1:2:1, while the phenotypic ratio is 3 tall : 1 dwarf. The result demonstrates segregation of alleles and the dominance of one allele over another This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2744 Marks 8. Heredity Differentiate genotype and phenotype and explain how genes influence characteristics Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Genotype refers to the genetic constitution of an organism for a particular trait, whereas phenotype refers to the observable expression of that trait. For example, in pea plants, TT and Tt may both produce a tall phenotype if T is dominant, while tt produces a dwarf phenotype. Genes influence characteristics by carrying information that controls the production of proteins or functional molecules. These products influence biological processes and visible traits. However, phenotype can also be influenced by environmental conditions. Therefore, genotype provides the genetic potential, while phenotype represents the resulting observable characteristic A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2754 Marks 8. Heredity Explain sex determination in humans using the role of X and Y chromosomes Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
In humans, females generally have XX sex chromosomes and males have XY. The egg produced by a female carries only an X chromosome. A male produces two types of sperm: some carry X and others carry Y. If an X-carrying sperm fertilises the egg, the zygote becomes XX and typically develops as female. If a Y-carrying sperm fertilises the egg, the zygote becomes XY and typically develops as male. Therefore, the type of sperm involved in fertilisation determines the chromosomal sex of the child. This also explains why the father contributes either an X or a Y chromosome Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2764 Marks 8. Heredity Explain acquired and inherited traits and discuss their significance in heredity Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Inherited traits are characteristics transmitted genetically from parents to offspring through genes. Examples include blood group and certain genetic features. Acquired traits develop during an individual's lifetime due to environmental influences, learning or changes in body tissues and are generally not transmitted genetically to offspring. For example, increased muscle strength from training is an acquired characteristic. Heredity mainly concerns transmission of genetic information from one generation to the next. Variations in inherited traits provide the raw material for natural selection, while acquired changes generally do not contribute directly to genetic evolution unless they involve heritable genetic changes A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2774 Marks 8. Heredity Explain how variations and natural selection can contribute to evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variation means differences among individuals of a population. Some variations are inherited and may arise from genetic recombination or changes in DNA. When environmental conditions change, individuals possessing certain advantageous inherited variations may have better chances of survival and reproduction. Their favourable traits can therefore become more common in later generations. This process is called natural selection. Over very long periods, accumulation of inherited differences can produce major changes in populations and may contribute to formation of new species. Thus, evolution is closely connected with heritable variation and differential survival and reproduction For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2784 Marks 8. Heredity Explain Mendel's monohybrid cross and derive the phenotypic ratio obtained Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Mendel studied inheritance using pea plants and considered contrasting traits. Suppose tallness is dominant over dwarfness. A pure tall plant with genotype TT is crossed with a pure dwarf plant tt. All F1 offspring receive T from one parent and t from the other, so their genotype is Tt and phenotype is tall. When F1 plants are crossed, Tt × Tt produces TT, Tt, Tt and tt. Thus, the genotypic ratio is 1:2:1, while the phenotypic ratio is 3 tall : 1 dwarf. The result demonstrates segregation of alleles and the dominance of one allele over another This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2794 Marks 8. Heredity Differentiate genotype and phenotype and explain how genes influence characteristics Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Genotype refers to the genetic constitution of an organism for a particular trait, whereas phenotype refers to the observable expression of that trait. For example, in pea plants, TT and Tt may both produce a tall phenotype if T is dominant, while tt produces a dwarf phenotype. Genes influence characteristics by carrying information that controls the production of proteins or functional molecules. These products influence biological processes and visible traits. However, phenotype can also be influenced by environmental conditions. Therefore, genotype provides the genetic potential, while phenotype represents the resulting observable characteristic A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2804 Marks 8. Heredity Explain sex determination in humans using the role of X and Y chromosomes Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
In humans, females generally have XX sex chromosomes and males have XY. The egg produced by a female carries only an X chromosome. A male produces two types of sperm: some carry X and others carry Y. If an X-carrying sperm fertilises the egg, the zygote becomes XX and typically develops as female. If a Y-carrying sperm fertilises the egg, the zygote becomes XY and typically develops as male. Therefore, the type of sperm involved in fertilisation determines the chromosomal sex of the child. This also explains why the father contributes either an X or a Y chromosome Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2814 Marks 8. Heredity Explain acquired and inherited traits and discuss their significance in heredity Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Inherited traits are characteristics transmitted genetically from parents to offspring through genes. Examples include blood group and certain genetic features. Acquired traits develop during an individual's lifetime due to environmental influences, learning or changes in body tissues and are generally not transmitted genetically to offspring. For example, increased muscle strength from training is an acquired characteristic. Heredity mainly concerns transmission of genetic information from one generation to the next. Variations in inherited traits provide the raw material for natural selection, while acquired changes generally do not contribute directly to genetic evolution unless they involve heritable genetic changes A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2824 Marks 8. Heredity Explain how variations and natural selection can contribute to evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variation means differences among individuals of a population. Some variations are inherited and may arise from genetic recombination or changes in DNA. When environmental conditions change, individuals possessing certain advantageous inherited variations may have better chances of survival and reproduction. Their favourable traits can therefore become more common in later generations. This process is called natural selection. Over very long periods, accumulation of inherited differences can produce major changes in populations and may contribute to formation of new species. Thus, evolution is closely connected with heritable variation and differential survival and reproduction For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2834 Marks 8. Heredity Explain Mendel's monohybrid cross and derive the phenotypic ratio obtained Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Mendel studied inheritance using pea plants and considered contrasting traits. Suppose tallness is dominant over dwarfness. A pure tall plant with genotype TT is crossed with a pure dwarf plant tt. All F1 offspring receive T from one parent and t from the other, so their genotype is Tt and phenotype is tall. When F1 plants are crossed, Tt × Tt produces TT, Tt, Tt and tt. Thus, the genotypic ratio is 1:2:1, while the phenotypic ratio is 3 tall : 1 dwarf. The result demonstrates segregation of alleles and the dominance of one allele over another This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2844 Marks 8. Heredity Differentiate genotype and phenotype and explain how genes influence characteristics Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Genotype refers to the genetic constitution of an organism for a particular trait, whereas phenotype refers to the observable expression of that trait. For example, in pea plants, TT and Tt may both produce a tall phenotype if T is dominant, while tt produces a dwarf phenotype. Genes influence characteristics by carrying information that controls the production of proteins or functional molecules. These products influence biological processes and visible traits. However, phenotype can also be influenced by environmental conditions. Therefore, genotype provides the genetic potential, while phenotype represents the resulting observable characteristic A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2854 Marks 8. Heredity Explain sex determination in humans using the role of X and Y chromosomes Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
In humans, females generally have XX sex chromosomes and males have XY. The egg produced by a female carries only an X chromosome. A male produces two types of sperm: some carry X and others carry Y. If an X-carrying sperm fertilises the egg, the zygote becomes XX and typically develops as female. If a Y-carrying sperm fertilises the egg, the zygote becomes XY and typically develops as male. Therefore, the type of sperm involved in fertilisation determines the chromosomal sex of the child. This also explains why the father contributes either an X or a Y chromosome Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2864 Marks 8. Heredity Explain acquired and inherited traits and discuss their significance in heredity Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Inherited traits are characteristics transmitted genetically from parents to offspring through genes. Examples include blood group and certain genetic features. Acquired traits develop during an individual's lifetime due to environmental influences, learning or changes in body tissues and are generally not transmitted genetically to offspring. For example, increased muscle strength from training is an acquired characteristic. Heredity mainly concerns transmission of genetic information from one generation to the next. Variations in inherited traits provide the raw material for natural selection, while acquired changes generally do not contribute directly to genetic evolution unless they involve heritable genetic changes A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2874 Marks 8. Heredity Explain how variations and natural selection can contribute to evolution Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Variation means differences among individuals of a population. Some variations are inherited and may arise from genetic recombination or changes in DNA. When environmental conditions change, individuals possessing certain advantageous inherited variations may have better chances of survival and reproduction. Their favourable traits can therefore become more common in later generations. This process is called natural selection. Over very long periods, accumulation of inherited differences can produce major changes in populations and may contribute to formation of new species. Thus, evolution is closely connected with heritable variation and differential survival and reproduction For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2884 Marks 8. Heredity Explain Mendel's monohybrid cross and derive the phenotypic ratio obtained Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Mendel studied inheritance using pea plants and considered contrasting traits. Suppose tallness is dominant over dwarfness. A pure tall plant with genotype TT is crossed with a pure dwarf plant tt. All F1 offspring receive T from one parent and t from the other, so their genotype is Tt and phenotype is tall. When F1 plants are crossed, Tt × Tt produces TT, Tt, Tt and tt. Thus, the genotypic ratio is 1:2:1, while the phenotypic ratio is 3 tall : 1 dwarf. The result demonstrates segregation of alleles and the dominance of one allele over another This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2894 Marks 9. Light – Reflection and Refraction Explain image formation by a concave mirror for different object positions using ray principles. Click to View Answer ▼
Answer:
A concave mirror can form different types of images depending on the position of the object. When the object is beyond the centre of curvature, the image forms between the focus and centre, and is real, inverted and diminished. When the object is at the centre, the image is formed at the centre and is real, inverted and of equal size. When the object lies between the centre and focus, the image forms beyond the centre and is enlarged. If the object is between focus and pole, the image is virtual, erect and magnified. These results are obtained by tracing standard rays parallel to the principal axis and through the focus or centre of curvature.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2904 Marks 9. Light – Reflection and Refraction Explain refraction of light and the factors that determine the amount of bending. Click to View Answer ▼
Answer:
Refraction is the change in direction of light when it passes obliquely from one transparent medium to another because its speed changes. Light bends toward the normal when it enters an optically denser medium and away from the normal when it enters a rarer medium. The amount of bending depends on the optical properties of the two media and the angle of incidence. Snell's law relates the angles of incidence and refraction through the refractive index. Refraction explains phenomena such as apparent depth, bending of a pencil in water and image formation by lenses. It is therefore fundamental to many optical instruments.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2914 Marks 9. Light – Reflection and Refraction Derive the lens formula conceptually and explain the meaning of magnification for a convex lens. Click to View Answer ▼
Answer:
For a thin spherical lens, the relationship among object distance, image distance and focal length is expressed by the lens formula, 1/f = 1/v − 1/u, using the standard Cartesian sign convention. Magnification is the ratio of image height to object height and can also be written as m = v/u for a thin lens with the appropriate sign convention. A positive magnification indicates an erect image, while a negative value indicates an inverted image. For a convex lens, an object beyond 2F forms a real, inverted and diminished image between F and 2F. These relationships help predict image position and size.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2924 Marks 9. Light – Reflection and Refraction Explain total internal reflection and discuss two important applications. Click to View Answer ▼
Answer:
Total internal reflection occurs when light travels from an optically denser medium to a rarer medium and the angle of incidence exceeds the critical angle. Under these conditions, the light is completely reflected back into the denser medium rather than refracting out. This principle is used in optical fibres, where light can travel long distances through repeated internal reflection with relatively low loss. It is also responsible for the brilliance of properly cut diamonds because light can undergo repeated internal reflection inside the stone. Total internal reflection demonstrates how the direction and path of light depend strongly on the optical properties of materials.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2934 Marks 9. Light – Reflection and Refraction Explain the working principle of a convex lens and discuss image formation at important object positions. Click to View Answer ▼
Answer:
A convex lens converges parallel rays toward its principal focus. When an object is beyond 2F, the image is formed between F and 2F and is real, inverted and smaller. At 2F, the image forms at 2F and is of equal size. Between F and 2F, the image forms beyond 2F and is enlarged. At F, refracted rays emerge parallel and the image is effectively formed at infinity. When the object lies between F and the optical centre, the lens forms a virtual, erect and magnified image. These principles are used in cameras, magnifying glasses and projectors.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2944 Marks 9. Light – Reflection and Refraction Explain image formation by a concave mirror for different object positions using ray principles Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A concave mirror can form different types of images depending on the position of the object. When the object is beyond the centre of curvature, the image forms between the focus and centre, and is real, inverted and diminished. When the object is at the centre, the image is formed at the centre and is real, inverted and of equal size. When the object lies between the centre and focus, the image forms beyond the centre and is enlarged. If the object is between focus and pole, the image is virtual, erect and magnified. These results are obtained by tracing standard rays parallel to the principal axis and through the focus or centre of curvature This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2954 Marks 9. Light – Reflection and Refraction Explain refraction of light and the factors that determine the amount of bending Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Refraction is the change in direction of light when it passes obliquely from one transparent medium to another because its speed changes. Light bends toward the normal when it enters an optically denser medium and away from the normal when it enters a rarer medium. The amount of bending depends on the optical properties of the two media and the angle of incidence. Snell's law relates the angles of incidence and refraction through the refractive index. Refraction explains phenomena such as apparent depth, bending of a pencil in water and image formation by lenses. It is therefore fundamental to many optical instruments A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2964 Marks 9. Light – Reflection and Refraction Derive the lens formula conceptually and explain the meaning of magnification for a convex lens Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
For a thin spherical lens, the relationship among object distance, image distance and focal length is expressed by the lens formula, 1/f = 1/v − 1/u, using the standard Cartesian sign convention. Magnification is the ratio of image height to object height and can also be written as m = v/u for a thin lens with the appropriate sign convention. A positive magnification indicates an erect image, while a negative value indicates an inverted image. For a convex lens, an object beyond 2F forms a real, inverted and diminished image between F and 2F. These relationships help predict image position and size Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2974 Marks 9. Light – Reflection and Refraction Explain total internal reflection and discuss two important applications Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Total internal reflection occurs when light travels from an optically denser medium to a rarer medium and the angle of incidence exceeds the critical angle. Under these conditions, the light is completely reflected back into the denser medium rather than refracting out. This principle is used in optical fibres, where light can travel long distances through repeated internal reflection with relatively low loss. It is also responsible for the brilliance of properly cut diamonds because light can undergo repeated internal reflection inside the stone. Total internal reflection demonstrates how the direction and path of light depend strongly on the optical properties of materials A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2984 Marks 9. Light – Reflection and Refraction Explain the working principle of a convex lens and discuss image formation at important object positions Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A convex lens converges parallel rays toward its principal focus. When an object is beyond 2F, the image is formed between F and 2F and is real, inverted and smaller. At 2F, the image forms at 2F and is of equal size. Between F and 2F, the image forms beyond 2F and is enlarged. At F, refracted rays emerge parallel and the image is effectively formed at infinity. When the object lies between F and the optical centre, the lens forms a virtual, erect and magnified image. These principles are used in cameras, magnifying glasses and projectors For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 2994 Marks 9. Light – Reflection and Refraction Explain image formation by a concave mirror for different object positions using ray principles Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A concave mirror can form different types of images depending on the position of the object. When the object is beyond the centre of curvature, the image forms between the focus and centre, and is real, inverted and diminished. When the object is at the centre, the image is formed at the centre and is real, inverted and of equal size. When the object lies between the centre and focus, the image forms beyond the centre and is enlarged. If the object is between focus and pole, the image is virtual, erect and magnified. These results are obtained by tracing standard rays parallel to the principal axis and through the focus or centre of curvature This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3004 Marks 9. Light – Reflection and Refraction Explain refraction of light and the factors that determine the amount of bending Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Refraction is the change in direction of light when it passes obliquely from one transparent medium to another because its speed changes. Light bends toward the normal when it enters an optically denser medium and away from the normal when it enters a rarer medium. The amount of bending depends on the optical properties of the two media and the angle of incidence. Snell's law relates the angles of incidence and refraction through the refractive index. Refraction explains phenomena such as apparent depth, bending of a pencil in water and image formation by lenses. It is therefore fundamental to many optical instruments A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3014 Marks 9. Light – Reflection and Refraction Derive the lens formula conceptually and explain the meaning of magnification for a convex lens Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
For a thin spherical lens, the relationship among object distance, image distance and focal length is expressed by the lens formula, 1/f = 1/v − 1/u, using the standard Cartesian sign convention. Magnification is the ratio of image height to object height and can also be written as m = v/u for a thin lens with the appropriate sign convention. A positive magnification indicates an erect image, while a negative value indicates an inverted image. For a convex lens, an object beyond 2F forms a real, inverted and diminished image between F and 2F. These relationships help predict image position and size Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3024 Marks 9. Light – Reflection and Refraction Explain total internal reflection and discuss two important applications Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Total internal reflection occurs when light travels from an optically denser medium to a rarer medium and the angle of incidence exceeds the critical angle. Under these conditions, the light is completely reflected back into the denser medium rather than refracting out. This principle is used in optical fibres, where light can travel long distances through repeated internal reflection with relatively low loss. It is also responsible for the brilliance of properly cut diamonds because light can undergo repeated internal reflection inside the stone. Total internal reflection demonstrates how the direction and path of light depend strongly on the optical properties of materials A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3034 Marks 9. Light – Reflection and Refraction Explain the working principle of a convex lens and discuss image formation at important object positions Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A convex lens converges parallel rays toward its principal focus. When an object is beyond 2F, the image is formed between F and 2F and is real, inverted and smaller. At 2F, the image forms at 2F and is of equal size. Between F and 2F, the image forms beyond 2F and is enlarged. At F, refracted rays emerge parallel and the image is effectively formed at infinity. When the object lies between F and the optical centre, the lens forms a virtual, erect and magnified image. These principles are used in cameras, magnifying glasses and projectors For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3044 Marks 9. Light – Reflection and Refraction Explain image formation by a concave mirror for different object positions using ray principles Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A concave mirror can form different types of images depending on the position of the object. When the object is beyond the centre of curvature, the image forms between the focus and centre, and is real, inverted and diminished. When the object is at the centre, the image is formed at the centre and is real, inverted and of equal size. When the object lies between the centre and focus, the image forms beyond the centre and is enlarged. If the object is between focus and pole, the image is virtual, erect and magnified. These results are obtained by tracing standard rays parallel to the principal axis and through the focus or centre of curvature This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3054 Marks 9. Light – Reflection and Refraction Explain refraction of light and the factors that determine the amount of bending Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Refraction is the change in direction of light when it passes obliquely from one transparent medium to another because its speed changes. Light bends toward the normal when it enters an optically denser medium and away from the normal when it enters a rarer medium. The amount of bending depends on the optical properties of the two media and the angle of incidence. Snell's law relates the angles of incidence and refraction through the refractive index. Refraction explains phenomena such as apparent depth, bending of a pencil in water and image formation by lenses. It is therefore fundamental to many optical instruments A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3064 Marks 9. Light – Reflection and Refraction Derive the lens formula conceptually and explain the meaning of magnification for a convex lens Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
For a thin spherical lens, the relationship among object distance, image distance and focal length is expressed by the lens formula, 1/f = 1/v − 1/u, using the standard Cartesian sign convention. Magnification is the ratio of image height to object height and can also be written as m = v/u for a thin lens with the appropriate sign convention. A positive magnification indicates an erect image, while a negative value indicates an inverted image. For a convex lens, an object beyond 2F forms a real, inverted and diminished image between F and 2F. These relationships help predict image position and size Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3074 Marks 9. Light – Reflection and Refraction Explain total internal reflection and discuss two important applications Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Total internal reflection occurs when light travels from an optically denser medium to a rarer medium and the angle of incidence exceeds the critical angle. Under these conditions, the light is completely reflected back into the denser medium rather than refracting out. This principle is used in optical fibres, where light can travel long distances through repeated internal reflection with relatively low loss. It is also responsible for the brilliance of properly cut diamonds because light can undergo repeated internal reflection inside the stone. Total internal reflection demonstrates how the direction and path of light depend strongly on the optical properties of materials A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3084 Marks 9. Light – Reflection and Refraction Explain the working principle of a convex lens and discuss image formation at important object positions Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A convex lens converges parallel rays toward its principal focus. When an object is beyond 2F, the image is formed between F and 2F and is real, inverted and smaller. At 2F, the image forms at 2F and is of equal size. Between F and 2F, the image forms beyond 2F and is enlarged. At F, refracted rays emerge parallel and the image is effectively formed at infinity. When the object lies between F and the optical centre, the lens forms a virtual, erect and magnified image. These principles are used in cameras, magnifying glasses and projectors For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3094 Marks 9. Light – Reflection and Refraction Explain image formation by a concave mirror for different object positions using ray principles Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A concave mirror can form different types of images depending on the position of the object. When the object is beyond the centre of curvature, the image forms between the focus and centre, and is real, inverted and diminished. When the object is at the centre, the image is formed at the centre and is real, inverted and of equal size. When the object lies between the centre and focus, the image forms beyond the centre and is enlarged. If the object is between focus and pole, the image is virtual, erect and magnified. These results are obtained by tracing standard rays parallel to the principal axis and through the focus or centre of curvature This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3104 Marks 9. Light – Reflection and Refraction Explain refraction of light and the factors that determine the amount of bending Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Refraction is the change in direction of light when it passes obliquely from one transparent medium to another because its speed changes. Light bends toward the normal when it enters an optically denser medium and away from the normal when it enters a rarer medium. The amount of bending depends on the optical properties of the two media and the angle of incidence. Snell's law relates the angles of incidence and refraction through the refractive index. Refraction explains phenomena such as apparent depth, bending of a pencil in water and image formation by lenses. It is therefore fundamental to many optical instruments A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3114 Marks 9. Light – Reflection and Refraction Derive the lens formula conceptually and explain the meaning of magnification for a convex lens Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
For a thin spherical lens, the relationship among object distance, image distance and focal length is expressed by the lens formula, 1/f = 1/v − 1/u, using the standard Cartesian sign convention. Magnification is the ratio of image height to object height and can also be written as m = v/u for a thin lens with the appropriate sign convention. A positive magnification indicates an erect image, while a negative value indicates an inverted image. For a convex lens, an object beyond 2F forms a real, inverted and diminished image between F and 2F. These relationships help predict image position and size Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3124 Marks 9. Light – Reflection and Refraction Explain total internal reflection and discuss two important applications Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Total internal reflection occurs when light travels from an optically denser medium to a rarer medium and the angle of incidence exceeds the critical angle. Under these conditions, the light is completely reflected back into the denser medium rather than refracting out. This principle is used in optical fibres, where light can travel long distances through repeated internal reflection with relatively low loss. It is also responsible for the brilliance of properly cut diamonds because light can undergo repeated internal reflection inside the stone. Total internal reflection demonstrates how the direction and path of light depend strongly on the optical properties of materials A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3134 Marks 9. Light – Reflection and Refraction Explain the working principle of a convex lens and discuss image formation at important object positions Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A convex lens converges parallel rays toward its principal focus. When an object is beyond 2F, the image is formed between F and 2F and is real, inverted and smaller. At 2F, the image forms at 2F and is of equal size. Between F and 2F, the image forms beyond 2F and is enlarged. At F, refracted rays emerge parallel and the image is effectively formed at infinity. When the object lies between F and the optical centre, the lens forms a virtual, erect and magnified image. These principles are used in cameras, magnifying glasses and projectors For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3144 Marks 9. Light – Reflection and Refraction Explain image formation by a concave mirror for different object positions using ray principles Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A concave mirror can form different types of images depending on the position of the object. When the object is beyond the centre of curvature, the image forms between the focus and centre, and is real, inverted and diminished. When the object is at the centre, the image is formed at the centre and is real, inverted and of equal size. When the object lies between the centre and focus, the image forms beyond the centre and is enlarged. If the object is between focus and pole, the image is virtual, erect and magnified. These results are obtained by tracing standard rays parallel to the principal axis and through the focus or centre of curvature This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3154 Marks 9. Light – Reflection and Refraction Explain refraction of light and the factors that determine the amount of bending Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Refraction is the change in direction of light when it passes obliquely from one transparent medium to another because its speed changes. Light bends toward the normal when it enters an optically denser medium and away from the normal when it enters a rarer medium. The amount of bending depends on the optical properties of the two media and the angle of incidence. Snell's law relates the angles of incidence and refraction through the refractive index. Refraction explains phenomena such as apparent depth, bending of a pencil in water and image formation by lenses. It is therefore fundamental to many optical instruments A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3164 Marks 9. Light – Reflection and Refraction Derive the lens formula conceptually and explain the meaning of magnification for a convex lens Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
For a thin spherical lens, the relationship among object distance, image distance and focal length is expressed by the lens formula, 1/f = 1/v − 1/u, using the standard Cartesian sign convention. Magnification is the ratio of image height to object height and can also be written as m = v/u for a thin lens with the appropriate sign convention. A positive magnification indicates an erect image, while a negative value indicates an inverted image. For a convex lens, an object beyond 2F forms a real, inverted and diminished image between F and 2F. These relationships help predict image position and size Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3174 Marks 9. Light – Reflection and Refraction Explain total internal reflection and discuss two important applications Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Total internal reflection occurs when light travels from an optically denser medium to a rarer medium and the angle of incidence exceeds the critical angle. Under these conditions, the light is completely reflected back into the denser medium rather than refracting out. This principle is used in optical fibres, where light can travel long distances through repeated internal reflection with relatively low loss. It is also responsible for the brilliance of properly cut diamonds because light can undergo repeated internal reflection inside the stone. Total internal reflection demonstrates how the direction and path of light depend strongly on the optical properties of materials A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3184 Marks 9. Light – Reflection and Refraction Explain the working principle of a convex lens and discuss image formation at important object positions Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A convex lens converges parallel rays toward its principal focus. When an object is beyond 2F, the image is formed between F and 2F and is real, inverted and smaller. At 2F, the image forms at 2F and is of equal size. Between F and 2F, the image forms beyond 2F and is enlarged. At F, refracted rays emerge parallel and the image is effectively formed at infinity. When the object lies between F and the optical centre, the lens forms a virtual, erect and magnified image. These principles are used in cameras, magnifying glasses and projectors For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3194 Marks 9. Light – Reflection and Refraction Explain image formation by a concave mirror for different object positions using ray principles Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A concave mirror can form different types of images depending on the position of the object. When the object is beyond the centre of curvature, the image forms between the focus and centre, and is real, inverted and diminished. When the object is at the centre, the image is formed at the centre and is real, inverted and of equal size. When the object lies between the centre and focus, the image forms beyond the centre and is enlarged. If the object is between focus and pole, the image is virtual, erect and magnified. These results are obtained by tracing standard rays parallel to the principal axis and through the focus or centre of curvature This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3204 Marks 9. Light – Reflection and Refraction Explain refraction of light and the factors that determine the amount of bending Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Refraction is the change in direction of light when it passes obliquely from one transparent medium to another because its speed changes. Light bends toward the normal when it enters an optically denser medium and away from the normal when it enters a rarer medium. The amount of bending depends on the optical properties of the two media and the angle of incidence. Snell's law relates the angles of incidence and refraction through the refractive index. Refraction explains phenomena such as apparent depth, bending of a pencil in water and image formation by lenses. It is therefore fundamental to many optical instruments A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3214 Marks 9. Light – Reflection and Refraction Derive the lens formula conceptually and explain the meaning of magnification for a convex lens Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
For a thin spherical lens, the relationship among object distance, image distance and focal length is expressed by the lens formula, 1/f = 1/v − 1/u, using the standard Cartesian sign convention. Magnification is the ratio of image height to object height and can also be written as m = v/u for a thin lens with the appropriate sign convention. A positive magnification indicates an erect image, while a negative value indicates an inverted image. For a convex lens, an object beyond 2F forms a real, inverted and diminished image between F and 2F. These relationships help predict image position and size Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3224 Marks 9. Light – Reflection and Refraction Explain total internal reflection and discuss two important applications Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Total internal reflection occurs when light travels from an optically denser medium to a rarer medium and the angle of incidence exceeds the critical angle. Under these conditions, the light is completely reflected back into the denser medium rather than refracting out. This principle is used in optical fibres, where light can travel long distances through repeated internal reflection with relatively low loss. It is also responsible for the brilliance of properly cut diamonds because light can undergo repeated internal reflection inside the stone. Total internal reflection demonstrates how the direction and path of light depend strongly on the optical properties of materials A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3234 Marks 9. Light – Reflection and Refraction Explain the working principle of a convex lens and discuss image formation at important object positions Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A convex lens converges parallel rays toward its principal focus. When an object is beyond 2F, the image is formed between F and 2F and is real, inverted and smaller. At 2F, the image forms at 2F and is of equal size. Between F and 2F, the image forms beyond 2F and is enlarged. At F, refracted rays emerge parallel and the image is effectively formed at infinity. When the object lies between F and the optical centre, the lens forms a virtual, erect and magnified image. These principles are used in cameras, magnifying glasses and projectors For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3244 Marks 9. Light – Reflection and Refraction Explain image formation by a concave mirror for different object positions using ray principles Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A concave mirror can form different types of images depending on the position of the object. When the object is beyond the centre of curvature, the image forms between the focus and centre, and is real, inverted and diminished. When the object is at the centre, the image is formed at the centre and is real, inverted and of equal size. When the object lies between the centre and focus, the image forms beyond the centre and is enlarged. If the object is between focus and pole, the image is virtual, erect and magnified. These results are obtained by tracing standard rays parallel to the principal axis and through the focus or centre of curvature This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3254 Marks 10. The Human Eye and the Colourful World Explain the structure of the human eye and the process of image formation on the retina. Click to View Answer ▼
Answer:
The human eye is a complex optical organ. The cornea provides most of the initial refraction of light, while the iris controls the amount of light entering through the pupil. The eye lens is a transparent, flexible structure that changes curvature to focus light. The ciliary muscles help adjust the focal length of the lens. Light is focused on the retina, which contains light-sensitive cells. These cells convert light information into electrical signals that travel through the optic nerve to the brain. The brain interprets these signals as vision. Thus, the eye combines optical focusing, light detection and neural processing.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3264 Marks 10. The Human Eye and the Colourful World Explain myopia and hypermetropia, their causes and correction. Click to View Answer ▼
Answer:
Myopia is a vision defect in which a person can see nearby objects clearly but distant objects appear blurred. It occurs when the eye forms the image of a distant object in front of the retina, often because the eyeball is elongated or the converging power is too high. It is corrected using a concave lens, which diverges incoming rays before they enter the eye. Hypermetropia is the opposite type of focusing defect: nearby objects appear blurred because the image tends to form behind the retina. It can be corrected using a convex lens. Suitable lenses restore proper focusing on the retina.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3274 Marks 10. The Human Eye and the Colourful World Explain accommodation of the eye and why its ability changes with age. Click to View Answer ▼
Answer:
Accommodation is the ability of the eye lens to change its focal length so that objects at different distances can be focused clearly on the retina. For distant objects, the ciliary muscles relax and the lens becomes relatively thin, reducing its converging power. For nearby objects, the ciliary muscles contract and the lens becomes more curved, increasing its power. With age, the lens may become less flexible and the ciliary muscles may become less effective. This reduces accommodation and can cause presbyopia. Corrective lenses, often designed according to individual requirements, can help provide clear vision.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3284 Marks 10. The Human Eye and the Colourful World Explain dispersion of white light and relate it to formation of a spectrum. Click to View Answer ▼
Answer:
Dispersion is the splitting of white light into its component colours when it passes through a transparent medium such as a prism. Different colours travel at different speeds in the medium and therefore undergo different amounts of refraction. Violet deviates more and red deviates less in a typical glass prism. The resulting band of colours is called a spectrum. The colours are commonly represented as violet, indigo, blue, green, yellow, orange and red. A rainbow is a natural example involving refraction, dispersion and internal reflection of sunlight by water droplets. Dispersion demonstrates that white light is a mixture of different wavelengths.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3294 Marks 10. The Human Eye and the Colourful World Explain atmospheric refraction and use it to explain twinkling of stars and advanced sunrise. Click to View Answer ▼
Answer:
Atmospheric refraction occurs because the atmosphere consists of layers of air with different temperatures and densities, and therefore different refractive indices. Light passing through these layers bends continuously. Stars are very distant point sources, and their apparent position and brightness can fluctuate as their light passes through changing atmospheric layers. This produces the twinkling effect. Atmospheric refraction also causes the Sun to be visible slightly before actual sunrise and for a short time after actual sunset. These effects show that the atmosphere can alter the apparent position and brightness of celestial objects.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3304 Marks 10. The Human Eye and the Colourful World Explain the structure of the human eye and the process of image formation on the retina Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The human eye is a complex optical organ. The cornea provides most of the initial refraction of light, while the iris controls the amount of light entering through the pupil. The eye lens is a transparent, flexible structure that changes curvature to focus light. The ciliary muscles help adjust the focal length of the lens. Light is focused on the retina, which contains light-sensitive cells. These cells convert light information into electrical signals that travel through the optic nerve to the brain. The brain interprets these signals as vision. Thus, the eye combines optical focusing, light detection and neural processing This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3314 Marks 10. The Human Eye and the Colourful World Explain myopia and hypermetropia, their causes and correction Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Myopia is a vision defect in which a person can see nearby objects clearly but distant objects appear blurred. It occurs when the eye forms the image of a distant object in front of the retina, often because the eyeball is elongated or the converging power is too high. It is corrected using a concave lens, which diverges incoming rays before they enter the eye. Hypermetropia is the opposite type of focusing defect: nearby objects appear blurred because the image tends to form behind the retina. It can be corrected using a convex lens. Suitable lenses restore proper focusing on the retina A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3324 Marks 10. The Human Eye and the Colourful World Explain accommodation of the eye and why its ability changes with age Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Accommodation is the ability of the eye lens to change its focal length so that objects at different distances can be focused clearly on the retina. For distant objects, the ciliary muscles relax and the lens becomes relatively thin, reducing its converging power. For nearby objects, the ciliary muscles contract and the lens becomes more curved, increasing its power. With age, the lens may become less flexible and the ciliary muscles may become less effective. This reduces accommodation and can cause presbyopia. Corrective lenses, often designed according to individual requirements, can help provide clear vision Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3334 Marks 10. The Human Eye and the Colourful World Explain dispersion of white light and relate it to formation of a spectrum Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Dispersion is the splitting of white light into its component colours when it passes through a transparent medium such as a prism. Different colours travel at different speeds in the medium and therefore undergo different amounts of refraction. Violet deviates more and red deviates less in a typical glass prism. The resulting band of colours is called a spectrum. The colours are commonly represented as violet, indigo, blue, green, yellow, orange and red. A rainbow is a natural example involving refraction, dispersion and internal reflection of sunlight by water droplets. Dispersion demonstrates that white light is a mixture of different wavelengths A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3344 Marks 10. The Human Eye and the Colourful World Explain atmospheric refraction and use it to explain twinkling of stars and advanced sunrise Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Atmospheric refraction occurs because the atmosphere consists of layers of air with different temperatures and densities, and therefore different refractive indices. Light passing through these layers bends continuously. Stars are very distant point sources, and their apparent position and brightness can fluctuate as their light passes through changing atmospheric layers. This produces the twinkling effect. Atmospheric refraction also causes the Sun to be visible slightly before actual sunrise and for a short time after actual sunset. These effects show that the atmosphere can alter the apparent position and brightness of celestial objects For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3354 Marks 10. The Human Eye and the Colourful World Explain the structure of the human eye and the process of image formation on the retina Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The human eye is a complex optical organ. The cornea provides most of the initial refraction of light, while the iris controls the amount of light entering through the pupil. The eye lens is a transparent, flexible structure that changes curvature to focus light. The ciliary muscles help adjust the focal length of the lens. Light is focused on the retina, which contains light-sensitive cells. These cells convert light information into electrical signals that travel through the optic nerve to the brain. The brain interprets these signals as vision. Thus, the eye combines optical focusing, light detection and neural processing This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3364 Marks 10. The Human Eye and the Colourful World Explain myopia and hypermetropia, their causes and correction Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Myopia is a vision defect in which a person can see nearby objects clearly but distant objects appear blurred. It occurs when the eye forms the image of a distant object in front of the retina, often because the eyeball is elongated or the converging power is too high. It is corrected using a concave lens, which diverges incoming rays before they enter the eye. Hypermetropia is the opposite type of focusing defect: nearby objects appear blurred because the image tends to form behind the retina. It can be corrected using a convex lens. Suitable lenses restore proper focusing on the retina A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3374 Marks 10. The Human Eye and the Colourful World Explain accommodation of the eye and why its ability changes with age Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Accommodation is the ability of the eye lens to change its focal length so that objects at different distances can be focused clearly on the retina. For distant objects, the ciliary muscles relax and the lens becomes relatively thin, reducing its converging power. For nearby objects, the ciliary muscles contract and the lens becomes more curved, increasing its power. With age, the lens may become less flexible and the ciliary muscles may become less effective. This reduces accommodation and can cause presbyopia. Corrective lenses, often designed according to individual requirements, can help provide clear vision Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3384 Marks 10. The Human Eye and the Colourful World Explain dispersion of white light and relate it to formation of a spectrum Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Dispersion is the splitting of white light into its component colours when it passes through a transparent medium such as a prism. Different colours travel at different speeds in the medium and therefore undergo different amounts of refraction. Violet deviates more and red deviates less in a typical glass prism. The resulting band of colours is called a spectrum. The colours are commonly represented as violet, indigo, blue, green, yellow, orange and red. A rainbow is a natural example involving refraction, dispersion and internal reflection of sunlight by water droplets. Dispersion demonstrates that white light is a mixture of different wavelengths A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3394 Marks 10. The Human Eye and the Colourful World Explain atmospheric refraction and use it to explain twinkling of stars and advanced sunrise Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Atmospheric refraction occurs because the atmosphere consists of layers of air with different temperatures and densities, and therefore different refractive indices. Light passing through these layers bends continuously. Stars are very distant point sources, and their apparent position and brightness can fluctuate as their light passes through changing atmospheric layers. This produces the twinkling effect. Atmospheric refraction also causes the Sun to be visible slightly before actual sunrise and for a short time after actual sunset. These effects show that the atmosphere can alter the apparent position and brightness of celestial objects For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3404 Marks 10. The Human Eye and the Colourful World Explain the structure of the human eye and the process of image formation on the retina Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The human eye is a complex optical organ. The cornea provides most of the initial refraction of light, while the iris controls the amount of light entering through the pupil. The eye lens is a transparent, flexible structure that changes curvature to focus light. The ciliary muscles help adjust the focal length of the lens. Light is focused on the retina, which contains light-sensitive cells. These cells convert light information into electrical signals that travel through the optic nerve to the brain. The brain interprets these signals as vision. Thus, the eye combines optical focusing, light detection and neural processing This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3414 Marks 10. The Human Eye and the Colourful World Explain myopia and hypermetropia, their causes and correction Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Myopia is a vision defect in which a person can see nearby objects clearly but distant objects appear blurred. It occurs when the eye forms the image of a distant object in front of the retina, often because the eyeball is elongated or the converging power is too high. It is corrected using a concave lens, which diverges incoming rays before they enter the eye. Hypermetropia is the opposite type of focusing defect: nearby objects appear blurred because the image tends to form behind the retina. It can be corrected using a convex lens. Suitable lenses restore proper focusing on the retina A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3424 Marks 10. The Human Eye and the Colourful World Explain accommodation of the eye and why its ability changes with age Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Accommodation is the ability of the eye lens to change its focal length so that objects at different distances can be focused clearly on the retina. For distant objects, the ciliary muscles relax and the lens becomes relatively thin, reducing its converging power. For nearby objects, the ciliary muscles contract and the lens becomes more curved, increasing its power. With age, the lens may become less flexible and the ciliary muscles may become less effective. This reduces accommodation and can cause presbyopia. Corrective lenses, often designed according to individual requirements, can help provide clear vision Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3434 Marks 10. The Human Eye and the Colourful World Explain dispersion of white light and relate it to formation of a spectrum Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Dispersion is the splitting of white light into its component colours when it passes through a transparent medium such as a prism. Different colours travel at different speeds in the medium and therefore undergo different amounts of refraction. Violet deviates more and red deviates less in a typical glass prism. The resulting band of colours is called a spectrum. The colours are commonly represented as violet, indigo, blue, green, yellow, orange and red. A rainbow is a natural example involving refraction, dispersion and internal reflection of sunlight by water droplets. Dispersion demonstrates that white light is a mixture of different wavelengths A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3444 Marks 10. The Human Eye and the Colourful World Explain atmospheric refraction and use it to explain twinkling of stars and advanced sunrise Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Atmospheric refraction occurs because the atmosphere consists of layers of air with different temperatures and densities, and therefore different refractive indices. Light passing through these layers bends continuously. Stars are very distant point sources, and their apparent position and brightness can fluctuate as their light passes through changing atmospheric layers. This produces the twinkling effect. Atmospheric refraction also causes the Sun to be visible slightly before actual sunrise and for a short time after actual sunset. These effects show that the atmosphere can alter the apparent position and brightness of celestial objects For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3454 Marks 10. The Human Eye and the Colourful World Explain the structure of the human eye and the process of image formation on the retina Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The human eye is a complex optical organ. The cornea provides most of the initial refraction of light, while the iris controls the amount of light entering through the pupil. The eye lens is a transparent, flexible structure that changes curvature to focus light. The ciliary muscles help adjust the focal length of the lens. Light is focused on the retina, which contains light-sensitive cells. These cells convert light information into electrical signals that travel through the optic nerve to the brain. The brain interprets these signals as vision. Thus, the eye combines optical focusing, light detection and neural processing This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3464 Marks 10. The Human Eye and the Colourful World Explain myopia and hypermetropia, their causes and correction Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Myopia is a vision defect in which a person can see nearby objects clearly but distant objects appear blurred. It occurs when the eye forms the image of a distant object in front of the retina, often because the eyeball is elongated or the converging power is too high. It is corrected using a concave lens, which diverges incoming rays before they enter the eye. Hypermetropia is the opposite type of focusing defect: nearby objects appear blurred because the image tends to form behind the retina. It can be corrected using a convex lens. Suitable lenses restore proper focusing on the retina A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3474 Marks 10. The Human Eye and the Colourful World Explain accommodation of the eye and why its ability changes with age Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Accommodation is the ability of the eye lens to change its focal length so that objects at different distances can be focused clearly on the retina. For distant objects, the ciliary muscles relax and the lens becomes relatively thin, reducing its converging power. For nearby objects, the ciliary muscles contract and the lens becomes more curved, increasing its power. With age, the lens may become less flexible and the ciliary muscles may become less effective. This reduces accommodation and can cause presbyopia. Corrective lenses, often designed according to individual requirements, can help provide clear vision Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3484 Marks 10. The Human Eye and the Colourful World Explain dispersion of white light and relate it to formation of a spectrum Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Dispersion is the splitting of white light into its component colours when it passes through a transparent medium such as a prism. Different colours travel at different speeds in the medium and therefore undergo different amounts of refraction. Violet deviates more and red deviates less in a typical glass prism. The resulting band of colours is called a spectrum. The colours are commonly represented as violet, indigo, blue, green, yellow, orange and red. A rainbow is a natural example involving refraction, dispersion and internal reflection of sunlight by water droplets. Dispersion demonstrates that white light is a mixture of different wavelengths A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3494 Marks 10. The Human Eye and the Colourful World Explain atmospheric refraction and use it to explain twinkling of stars and advanced sunrise Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Atmospheric refraction occurs because the atmosphere consists of layers of air with different temperatures and densities, and therefore different refractive indices. Light passing through these layers bends continuously. Stars are very distant point sources, and their apparent position and brightness can fluctuate as their light passes through changing atmospheric layers. This produces the twinkling effect. Atmospheric refraction also causes the Sun to be visible slightly before actual sunrise and for a short time after actual sunset. These effects show that the atmosphere can alter the apparent position and brightness of celestial objects For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3504 Marks 10. The Human Eye and the Colourful World Explain the structure of the human eye and the process of image formation on the retina Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The human eye is a complex optical organ. The cornea provides most of the initial refraction of light, while the iris controls the amount of light entering through the pupil. The eye lens is a transparent, flexible structure that changes curvature to focus light. The ciliary muscles help adjust the focal length of the lens. Light is focused on the retina, which contains light-sensitive cells. These cells convert light information into electrical signals that travel through the optic nerve to the brain. The brain interprets these signals as vision. Thus, the eye combines optical focusing, light detection and neural processing This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3514 Marks 10. The Human Eye and the Colourful World Explain myopia and hypermetropia, their causes and correction Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Myopia is a vision defect in which a person can see nearby objects clearly but distant objects appear blurred. It occurs when the eye forms the image of a distant object in front of the retina, often because the eyeball is elongated or the converging power is too high. It is corrected using a concave lens, which diverges incoming rays before they enter the eye. Hypermetropia is the opposite type of focusing defect: nearby objects appear blurred because the image tends to form behind the retina. It can be corrected using a convex lens. Suitable lenses restore proper focusing on the retina A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3524 Marks 10. The Human Eye and the Colourful World Explain accommodation of the eye and why its ability changes with age Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Accommodation is the ability of the eye lens to change its focal length so that objects at different distances can be focused clearly on the retina. For distant objects, the ciliary muscles relax and the lens becomes relatively thin, reducing its converging power. For nearby objects, the ciliary muscles contract and the lens becomes more curved, increasing its power. With age, the lens may become less flexible and the ciliary muscles may become less effective. This reduces accommodation and can cause presbyopia. Corrective lenses, often designed according to individual requirements, can help provide clear vision Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3534 Marks 10. The Human Eye and the Colourful World Explain dispersion of white light and relate it to formation of a spectrum Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Dispersion is the splitting of white light into its component colours when it passes through a transparent medium such as a prism. Different colours travel at different speeds in the medium and therefore undergo different amounts of refraction. Violet deviates more and red deviates less in a typical glass prism. The resulting band of colours is called a spectrum. The colours are commonly represented as violet, indigo, blue, green, yellow, orange and red. A rainbow is a natural example involving refraction, dispersion and internal reflection of sunlight by water droplets. Dispersion demonstrates that white light is a mixture of different wavelengths A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3544 Marks 10. The Human Eye and the Colourful World Explain atmospheric refraction and use it to explain twinkling of stars and advanced sunrise Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Atmospheric refraction occurs because the atmosphere consists of layers of air with different temperatures and densities, and therefore different refractive indices. Light passing through these layers bends continuously. Stars are very distant point sources, and their apparent position and brightness can fluctuate as their light passes through changing atmospheric layers. This produces the twinkling effect. Atmospheric refraction also causes the Sun to be visible slightly before actual sunrise and for a short time after actual sunset. These effects show that the atmosphere can alter the apparent position and brightness of celestial objects For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3554 Marks 10. The Human Eye and the Colourful World Explain the structure of the human eye and the process of image formation on the retina Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The human eye is a complex optical organ. The cornea provides most of the initial refraction of light, while the iris controls the amount of light entering through the pupil. The eye lens is a transparent, flexible structure that changes curvature to focus light. The ciliary muscles help adjust the focal length of the lens. Light is focused on the retina, which contains light-sensitive cells. These cells convert light information into electrical signals that travel through the optic nerve to the brain. The brain interprets these signals as vision. Thus, the eye combines optical focusing, light detection and neural processing This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3564 Marks 10. The Human Eye and the Colourful World Explain myopia and hypermetropia, their causes and correction Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Myopia is a vision defect in which a person can see nearby objects clearly but distant objects appear blurred. It occurs when the eye forms the image of a distant object in front of the retina, often because the eyeball is elongated or the converging power is too high. It is corrected using a concave lens, which diverges incoming rays before they enter the eye. Hypermetropia is the opposite type of focusing defect: nearby objects appear blurred because the image tends to form behind the retina. It can be corrected using a convex lens. Suitable lenses restore proper focusing on the retina A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3574 Marks 10. The Human Eye and the Colourful World Explain accommodation of the eye and why its ability changes with age Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Accommodation is the ability of the eye lens to change its focal length so that objects at different distances can be focused clearly on the retina. For distant objects, the ciliary muscles relax and the lens becomes relatively thin, reducing its converging power. For nearby objects, the ciliary muscles contract and the lens becomes more curved, increasing its power. With age, the lens may become less flexible and the ciliary muscles may become less effective. This reduces accommodation and can cause presbyopia. Corrective lenses, often designed according to individual requirements, can help provide clear vision Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3584 Marks 10. The Human Eye and the Colourful World Explain dispersion of white light and relate it to formation of a spectrum Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Dispersion is the splitting of white light into its component colours when it passes through a transparent medium such as a prism. Different colours travel at different speeds in the medium and therefore undergo different amounts of refraction. Violet deviates more and red deviates less in a typical glass prism. The resulting band of colours is called a spectrum. The colours are commonly represented as violet, indigo, blue, green, yellow, orange and red. A rainbow is a natural example involving refraction, dispersion and internal reflection of sunlight by water droplets. Dispersion demonstrates that white light is a mixture of different wavelengths A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3594 Marks 10. The Human Eye and the Colourful World Explain atmospheric refraction and use it to explain twinkling of stars and advanced sunrise Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Atmospheric refraction occurs because the atmosphere consists of layers of air with different temperatures and densities, and therefore different refractive indices. Light passing through these layers bends continuously. Stars are very distant point sources, and their apparent position and brightness can fluctuate as their light passes through changing atmospheric layers. This produces the twinkling effect. Atmospheric refraction also causes the Sun to be visible slightly before actual sunrise and for a short time after actual sunset. These effects show that the atmosphere can alter the apparent position and brightness of celestial objects For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3604 Marks 10. The Human Eye and the Colourful World Explain the structure of the human eye and the process of image formation on the retina Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
The human eye is a complex optical organ. The cornea provides most of the initial refraction of light, while the iris controls the amount of light entering through the pupil. The eye lens is a transparent, flexible structure that changes curvature to focus light. The ciliary muscles help adjust the focal length of the lens. Light is focused on the retina, which contains light-sensitive cells. These cells convert light information into electrical signals that travel through the optic nerve to the brain. The brain interprets these signals as vision. Thus, the eye combines optical focusing, light detection and neural processing This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3614 Marks 11. Electricity Derive the equivalent resistance for resistors connected in series and explain the practical significance. Click to View Answer ▼
Answer:
In a series circuit, resistors are connected one after another so the same current flows through each resistor. If resistances are R₁, R₂ and R₃, the potential differences across them are V₁ = IR₁, V₂ = IR₂ and V₃ = IR₃. The total potential difference is V = V₁ + V₂ + V₃ = I(R₁ + R₂ + R₃). Therefore, the equivalent resistance is R = R₁ + R₂ + R₃. The total resistance is greater than any individual resistance. Series connection is useful when the same current must pass through components, but it is generally unsuitable for independent domestic appliances because failure of one component can interrupt the whole circuit.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3624 Marks 11. Electricity Derive the equivalent resistance of two or more resistors connected in parallel. Click to View Answer ▼
Answer:
In a parallel circuit, each resistor is connected across the same two points, so the potential difference across each is the same. For resistors R₁ and R₂, the currents are I₁ = V/R₁ and I₂ = V/R₂. The total current is I = I₁ + I₂. Therefore, I = V(1/R₁ + 1/R₂), giving 1/R = 1/R₁ + 1/R₂. For several resistors, the reciprocal of equivalent resistance equals the sum of reciprocals of individual resistances. The equivalent resistance is lower than the smallest individual resistance. This arrangement is widely used in domestic circuits because appliances can operate independently.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3634 Marks 11. Electricity Explain electric power, electrical energy and the commercial unit of electrical energy. Click to View Answer ▼
Answer:
Electric power is the rate at which electrical energy is consumed or converted. It is given by P = VI. Using Ohm's law, it can also be written as P = I²R or P = V²/R. The SI unit is watt. Electrical energy consumed over time is E = Pt. In practical billing, electrical energy is measured in kilowatt-hours (kWh). One kilowatt-hour is the energy consumed by a device of power 1 kW operating for 1 hour. Thus, a 1000 W appliance operating continuously for one hour consumes 1 kWh. Electricity bills are generally based on this commercial unit.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3644 Marks 11. Electricity Explain the heating effect of electric current and derive the relation for heat produced. Click to View Answer ▼
Answer:
When electric current flows through a resistance, electrical energy is converted into heat. This is called the heating effect of electric current. If a potential difference V drives current I through resistance R for time t, the electrical work done is W = VIt. Using Ohm's law V = IR, the heat produced becomes H = I²Rt. This relation is Joule's law of heating. The effect is useful in electric heaters, irons, toasters and fuses. The amount of heat depends on current, resistance and time. A fuse uses controlled heating to melt when excessive current flows, protecting the circuit.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3654 Marks 11. Electricity Explain domestic electric circuits, including live, neutral and earth wires and the role of a fuse. Click to View Answer ▼
Answer:
A domestic circuit normally uses live, neutral and earth wires. The live wire supplies electrical potential, while the neutral wire provides the return path. The earth wire is a safety connection that provides a low-resistance path for leakage current, reducing the risk of electric shock. Appliances are connected in parallel so each receives the required potential difference and can operate independently. A fuse is connected in series with the live wire and contains a thin wire designed to melt when excessive current flows. This breaks the circuit and protects appliances and wiring from damage caused by overload or short circuit.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3664 Marks 11. Electricity Derive the equivalent resistance for resistors connected in series and explain the practical significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
In a series circuit, resistors are connected one after another so the same current flows through each resistor. If resistances are R₁, R₂ and R₃, the potential differences across them are V₁ = IR₁, V₂ = IR₂ and V₃ = IR₃. The total potential difference is V = V₁ + V₂ + V₃ = I(R₁ + R₂ + R₃). Therefore, the equivalent resistance is R = R₁ + R₂ + R₃. The total resistance is greater than any individual resistance. Series connection is useful when the same current must pass through components, but it is generally unsuitable for independent domestic appliances because failure of one component can interrupt the whole circuit This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3674 Marks 11. Electricity Derive the equivalent resistance of two or more resistors connected in parallel Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In a parallel circuit, each resistor is connected across the same two points, so the potential difference across each is the same. For resistors R₁ and R₂, the currents are I₁ = V/R₁ and I₂ = V/R₂. The total current is I = I₁ + I₂. Therefore, I = V(1/R₁ + 1/R₂), giving 1/R = 1/R₁ + 1/R₂. For several resistors, the reciprocal of equivalent resistance equals the sum of reciprocals of individual resistances. The equivalent resistance is lower than the smallest individual resistance. This arrangement is widely used in domestic circuits because appliances can operate independently A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3684 Marks 11. Electricity Explain electric power, electrical energy and the commercial unit of electrical energy Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electric power is the rate at which electrical energy is consumed or converted. It is given by P = VI. Using Ohm's law, it can also be written as P = I²R or P = V²/R. The SI unit is watt. Electrical energy consumed over time is E = Pt. In practical billing, electrical energy is measured in kilowatt-hours (kWh). One kilowatt-hour is the energy consumed by a device of power 1 kW operating for 1 hour. Thus, a 1000 W appliance operating continuously for one hour consumes 1 kWh. Electricity bills are generally based on this commercial unit Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3694 Marks 11. Electricity Explain the heating effect of electric current and derive the relation for heat produced Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
When electric current flows through a resistance, electrical energy is converted into heat. This is called the heating effect of electric current. If a potential difference V drives current I through resistance R for time t, the electrical work done is W = VIt. Using Ohm's law V = IR, the heat produced becomes H = I²Rt. This relation is Joule's law of heating. The effect is useful in electric heaters, irons, toasters and fuses. The amount of heat depends on current, resistance and time. A fuse uses controlled heating to melt when excessive current flows, protecting the circuit A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3704 Marks 11. Electricity Explain domestic electric circuits, including live, neutral and earth wires and the role of a fuse Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A domestic circuit normally uses live, neutral and earth wires. The live wire supplies electrical potential, while the neutral wire provides the return path. The earth wire is a safety connection that provides a low-resistance path for leakage current, reducing the risk of electric shock. Appliances are connected in parallel so each receives the required potential difference and can operate independently. A fuse is connected in series with the live wire and contains a thin wire designed to melt when excessive current flows. This breaks the circuit and protects appliances and wiring from damage caused by overload or short circuit For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3714 Marks 11. Electricity Derive the equivalent resistance for resistors connected in series and explain the practical significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
In a series circuit, resistors are connected one after another so the same current flows through each resistor. If resistances are R₁, R₂ and R₃, the potential differences across them are V₁ = IR₁, V₂ = IR₂ and V₃ = IR₃. The total potential difference is V = V₁ + V₂ + V₃ = I(R₁ + R₂ + R₃). Therefore, the equivalent resistance is R = R₁ + R₂ + R₃. The total resistance is greater than any individual resistance. Series connection is useful when the same current must pass through components, but it is generally unsuitable for independent domestic appliances because failure of one component can interrupt the whole circuit This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3724 Marks 11. Electricity Derive the equivalent resistance of two or more resistors connected in parallel Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In a parallel circuit, each resistor is connected across the same two points, so the potential difference across each is the same. For resistors R₁ and R₂, the currents are I₁ = V/R₁ and I₂ = V/R₂. The total current is I = I₁ + I₂. Therefore, I = V(1/R₁ + 1/R₂), giving 1/R = 1/R₁ + 1/R₂. For several resistors, the reciprocal of equivalent resistance equals the sum of reciprocals of individual resistances. The equivalent resistance is lower than the smallest individual resistance. This arrangement is widely used in domestic circuits because appliances can operate independently A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3734 Marks 11. Electricity Explain electric power, electrical energy and the commercial unit of electrical energy Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electric power is the rate at which electrical energy is consumed or converted. It is given by P = VI. Using Ohm's law, it can also be written as P = I²R or P = V²/R. The SI unit is watt. Electrical energy consumed over time is E = Pt. In practical billing, electrical energy is measured in kilowatt-hours (kWh). One kilowatt-hour is the energy consumed by a device of power 1 kW operating for 1 hour. Thus, a 1000 W appliance operating continuously for one hour consumes 1 kWh. Electricity bills are generally based on this commercial unit Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3744 Marks 11. Electricity Explain the heating effect of electric current and derive the relation for heat produced Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
When electric current flows through a resistance, electrical energy is converted into heat. This is called the heating effect of electric current. If a potential difference V drives current I through resistance R for time t, the electrical work done is W = VIt. Using Ohm's law V = IR, the heat produced becomes H = I²Rt. This relation is Joule's law of heating. The effect is useful in electric heaters, irons, toasters and fuses. The amount of heat depends on current, resistance and time. A fuse uses controlled heating to melt when excessive current flows, protecting the circuit A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3754 Marks 11. Electricity Explain domestic electric circuits, including live, neutral and earth wires and the role of a fuse Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A domestic circuit normally uses live, neutral and earth wires. The live wire supplies electrical potential, while the neutral wire provides the return path. The earth wire is a safety connection that provides a low-resistance path for leakage current, reducing the risk of electric shock. Appliances are connected in parallel so each receives the required potential difference and can operate independently. A fuse is connected in series with the live wire and contains a thin wire designed to melt when excessive current flows. This breaks the circuit and protects appliances and wiring from damage caused by overload or short circuit For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3764 Marks 11. Electricity Derive the equivalent resistance for resistors connected in series and explain the practical significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
In a series circuit, resistors are connected one after another so the same current flows through each resistor. If resistances are R₁, R₂ and R₃, the potential differences across them are V₁ = IR₁, V₂ = IR₂ and V₃ = IR₃. The total potential difference is V = V₁ + V₂ + V₃ = I(R₁ + R₂ + R₃). Therefore, the equivalent resistance is R = R₁ + R₂ + R₃. The total resistance is greater than any individual resistance. Series connection is useful when the same current must pass through components, but it is generally unsuitable for independent domestic appliances because failure of one component can interrupt the whole circuit This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3774 Marks 11. Electricity Derive the equivalent resistance of two or more resistors connected in parallel Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In a parallel circuit, each resistor is connected across the same two points, so the potential difference across each is the same. For resistors R₁ and R₂, the currents are I₁ = V/R₁ and I₂ = V/R₂. The total current is I = I₁ + I₂. Therefore, I = V(1/R₁ + 1/R₂), giving 1/R = 1/R₁ + 1/R₂. For several resistors, the reciprocal of equivalent resistance equals the sum of reciprocals of individual resistances. The equivalent resistance is lower than the smallest individual resistance. This arrangement is widely used in domestic circuits because appliances can operate independently A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3784 Marks 11. Electricity Explain electric power, electrical energy and the commercial unit of electrical energy Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electric power is the rate at which electrical energy is consumed or converted. It is given by P = VI. Using Ohm's law, it can also be written as P = I²R or P = V²/R. The SI unit is watt. Electrical energy consumed over time is E = Pt. In practical billing, electrical energy is measured in kilowatt-hours (kWh). One kilowatt-hour is the energy consumed by a device of power 1 kW operating for 1 hour. Thus, a 1000 W appliance operating continuously for one hour consumes 1 kWh. Electricity bills are generally based on this commercial unit Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3794 Marks 11. Electricity Explain the heating effect of electric current and derive the relation for heat produced Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
When electric current flows through a resistance, electrical energy is converted into heat. This is called the heating effect of electric current. If a potential difference V drives current I through resistance R for time t, the electrical work done is W = VIt. Using Ohm's law V = IR, the heat produced becomes H = I²Rt. This relation is Joule's law of heating. The effect is useful in electric heaters, irons, toasters and fuses. The amount of heat depends on current, resistance and time. A fuse uses controlled heating to melt when excessive current flows, protecting the circuit A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3804 Marks 11. Electricity Explain domestic electric circuits, including live, neutral and earth wires and the role of a fuse Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A domestic circuit normally uses live, neutral and earth wires. The live wire supplies electrical potential, while the neutral wire provides the return path. The earth wire is a safety connection that provides a low-resistance path for leakage current, reducing the risk of electric shock. Appliances are connected in parallel so each receives the required potential difference and can operate independently. A fuse is connected in series with the live wire and contains a thin wire designed to melt when excessive current flows. This breaks the circuit and protects appliances and wiring from damage caused by overload or short circuit For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3814 Marks 11. Electricity Derive the equivalent resistance for resistors connected in series and explain the practical significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
In a series circuit, resistors are connected one after another so the same current flows through each resistor. If resistances are R₁, R₂ and R₃, the potential differences across them are V₁ = IR₁, V₂ = IR₂ and V₃ = IR₃. The total potential difference is V = V₁ + V₂ + V₃ = I(R₁ + R₂ + R₃). Therefore, the equivalent resistance is R = R₁ + R₂ + R₃. The total resistance is greater than any individual resistance. Series connection is useful when the same current must pass through components, but it is generally unsuitable for independent domestic appliances because failure of one component can interrupt the whole circuit This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3824 Marks 11. Electricity Derive the equivalent resistance of two or more resistors connected in parallel Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In a parallel circuit, each resistor is connected across the same two points, so the potential difference across each is the same. For resistors R₁ and R₂, the currents are I₁ = V/R₁ and I₂ = V/R₂. The total current is I = I₁ + I₂. Therefore, I = V(1/R₁ + 1/R₂), giving 1/R = 1/R₁ + 1/R₂. For several resistors, the reciprocal of equivalent resistance equals the sum of reciprocals of individual resistances. The equivalent resistance is lower than the smallest individual resistance. This arrangement is widely used in domestic circuits because appliances can operate independently A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3834 Marks 11. Electricity Explain electric power, electrical energy and the commercial unit of electrical energy Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electric power is the rate at which electrical energy is consumed or converted. It is given by P = VI. Using Ohm's law, it can also be written as P = I²R or P = V²/R. The SI unit is watt. Electrical energy consumed over time is E = Pt. In practical billing, electrical energy is measured in kilowatt-hours (kWh). One kilowatt-hour is the energy consumed by a device of power 1 kW operating for 1 hour. Thus, a 1000 W appliance operating continuously for one hour consumes 1 kWh. Electricity bills are generally based on this commercial unit Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3844 Marks 11. Electricity Explain the heating effect of electric current and derive the relation for heat produced Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
When electric current flows through a resistance, electrical energy is converted into heat. This is called the heating effect of electric current. If a potential difference V drives current I through resistance R for time t, the electrical work done is W = VIt. Using Ohm's law V = IR, the heat produced becomes H = I²Rt. This relation is Joule's law of heating. The effect is useful in electric heaters, irons, toasters and fuses. The amount of heat depends on current, resistance and time. A fuse uses controlled heating to melt when excessive current flows, protecting the circuit A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3854 Marks 11. Electricity Explain domestic electric circuits, including live, neutral and earth wires and the role of a fuse Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A domestic circuit normally uses live, neutral and earth wires. The live wire supplies electrical potential, while the neutral wire provides the return path. The earth wire is a safety connection that provides a low-resistance path for leakage current, reducing the risk of electric shock. Appliances are connected in parallel so each receives the required potential difference and can operate independently. A fuse is connected in series with the live wire and contains a thin wire designed to melt when excessive current flows. This breaks the circuit and protects appliances and wiring from damage caused by overload or short circuit For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3864 Marks 11. Electricity Derive the equivalent resistance for resistors connected in series and explain the practical significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
In a series circuit, resistors are connected one after another so the same current flows through each resistor. If resistances are R₁, R₂ and R₃, the potential differences across them are V₁ = IR₁, V₂ = IR₂ and V₃ = IR₃. The total potential difference is V = V₁ + V₂ + V₃ = I(R₁ + R₂ + R₃). Therefore, the equivalent resistance is R = R₁ + R₂ + R₃. The total resistance is greater than any individual resistance. Series connection is useful when the same current must pass through components, but it is generally unsuitable for independent domestic appliances because failure of one component can interrupt the whole circuit This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3874 Marks 11. Electricity Derive the equivalent resistance of two or more resistors connected in parallel Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In a parallel circuit, each resistor is connected across the same two points, so the potential difference across each is the same. For resistors R₁ and R₂, the currents are I₁ = V/R₁ and I₂ = V/R₂. The total current is I = I₁ + I₂. Therefore, I = V(1/R₁ + 1/R₂), giving 1/R = 1/R₁ + 1/R₂. For several resistors, the reciprocal of equivalent resistance equals the sum of reciprocals of individual resistances. The equivalent resistance is lower than the smallest individual resistance. This arrangement is widely used in domestic circuits because appliances can operate independently A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3884 Marks 11. Electricity Explain electric power, electrical energy and the commercial unit of electrical energy Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electric power is the rate at which electrical energy is consumed or converted. It is given by P = VI. Using Ohm's law, it can also be written as P = I²R or P = V²/R. The SI unit is watt. Electrical energy consumed over time is E = Pt. In practical billing, electrical energy is measured in kilowatt-hours (kWh). One kilowatt-hour is the energy consumed by a device of power 1 kW operating for 1 hour. Thus, a 1000 W appliance operating continuously for one hour consumes 1 kWh. Electricity bills are generally based on this commercial unit Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3894 Marks 11. Electricity Explain the heating effect of electric current and derive the relation for heat produced Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
When electric current flows through a resistance, electrical energy is converted into heat. This is called the heating effect of electric current. If a potential difference V drives current I through resistance R for time t, the electrical work done is W = VIt. Using Ohm's law V = IR, the heat produced becomes H = I²Rt. This relation is Joule's law of heating. The effect is useful in electric heaters, irons, toasters and fuses. The amount of heat depends on current, resistance and time. A fuse uses controlled heating to melt when excessive current flows, protecting the circuit A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3904 Marks 11. Electricity Explain domestic electric circuits, including live, neutral and earth wires and the role of a fuse Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A domestic circuit normally uses live, neutral and earth wires. The live wire supplies electrical potential, while the neutral wire provides the return path. The earth wire is a safety connection that provides a low-resistance path for leakage current, reducing the risk of electric shock. Appliances are connected in parallel so each receives the required potential difference and can operate independently. A fuse is connected in series with the live wire and contains a thin wire designed to melt when excessive current flows. This breaks the circuit and protects appliances and wiring from damage caused by overload or short circuit For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3914 Marks 11. Electricity Derive the equivalent resistance for resistors connected in series and explain the practical significance Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
In a series circuit, resistors are connected one after another so the same current flows through each resistor. If resistances are R₁, R₂ and R₃, the potential differences across them are V₁ = IR₁, V₂ = IR₂ and V₃ = IR₃. The total potential difference is V = V₁ + V₂ + V₃ = I(R₁ + R₂ + R₃). Therefore, the equivalent resistance is R = R₁ + R₂ + R₃. The total resistance is greater than any individual resistance. Series connection is useful when the same current must pass through components, but it is generally unsuitable for independent domestic appliances because failure of one component can interrupt the whole circuit This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3924 Marks 11. Electricity Derive the equivalent resistance of two or more resistors connected in parallel Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
In a parallel circuit, each resistor is connected across the same two points, so the potential difference across each is the same. For resistors R₁ and R₂, the currents are I₁ = V/R₁ and I₂ = V/R₂. The total current is I = I₁ + I₂. Therefore, I = V(1/R₁ + 1/R₂), giving 1/R = 1/R₁ + 1/R₂. For several resistors, the reciprocal of equivalent resistance equals the sum of reciprocals of individual resistances. The equivalent resistance is lower than the smallest individual resistance. This arrangement is widely used in domestic circuits because appliances can operate independently A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3934 Marks 11. Electricity Explain electric power, electrical energy and the commercial unit of electrical energy Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electric power is the rate at which electrical energy is consumed or converted. It is given by P = VI. Using Ohm's law, it can also be written as P = I²R or P = V²/R. The SI unit is watt. Electrical energy consumed over time is E = Pt. In practical billing, electrical energy is measured in kilowatt-hours (kWh). One kilowatt-hour is the energy consumed by a device of power 1 kW operating for 1 hour. Thus, a 1000 W appliance operating continuously for one hour consumes 1 kWh. Electricity bills are generally based on this commercial unit Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3944 Marks 11. Electricity Explain the heating effect of electric current and derive the relation for heat produced Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
When electric current flows through a resistance, electrical energy is converted into heat. This is called the heating effect of electric current. If a potential difference V drives current I through resistance R for time t, the electrical work done is W = VIt. Using Ohm's law V = IR, the heat produced becomes H = I²Rt. This relation is Joule's law of heating. The effect is useful in electric heaters, irons, toasters and fuses. The amount of heat depends on current, resistance and time. A fuse uses controlled heating to melt when excessive current flows, protecting the circuit A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3954 Marks 11. Electricity Explain domestic electric circuits, including live, neutral and earth wires and the role of a fuse Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A domestic circuit normally uses live, neutral and earth wires. The live wire supplies electrical potential, while the neutral wire provides the return path. The earth wire is a safety connection that provides a low-resistance path for leakage current, reducing the risk of electric shock. Appliances are connected in parallel so each receives the required potential difference and can operate independently. A fuse is connected in series with the live wire and contains a thin wire designed to melt when excessive current flows. This breaks the circuit and protects appliances and wiring from damage caused by overload or short circuit For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3964 Marks 12. Magnetic Effects of Electric Current Explain the magnetic field produced by a current-carrying straight conductor and the right-hand thumb rule. Click to View Answer ▼
Answer:
A current-carrying conductor produces a magnetic field around itself. For a straight conductor, the field lines form concentric circles in planes perpendicular to the conductor. The strength of the field increases when current increases and decreases as the distance from the conductor increases. The direction can be determined using the right-hand thumb rule: if the thumb of the right hand points in the direction of conventional current, the curled fingers indicate the direction of magnetic field lines. This principle demonstrates the connection between electric current and magnetism and forms the basis of many electromagnetic devices.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3974 Marks 12. Magnetic Effects of Electric Current Explain the construction and working principle of an electric motor. Click to View Answer ▼
Answer:
An electric motor converts electrical energy into mechanical energy. Its main components include a rectangular coil placed in a magnetic field, a split-ring commutator, brushes and a battery. When current passes through the coil, the two sides experience magnetic forces in opposite directions. These forces produce a turning effect that rotates the coil. After every half rotation, the split-ring commutator reverses the current direction in the coil, keeping the torque in the same rotational direction. The motor principle is therefore based on the force experienced by a current-carrying conductor placed in a magnetic field. Motors are widely used in fans, pumps and machines.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3984 Marks 12. Magnetic Effects of Electric Current Explain electromagnetic induction and the working principle of an electric generator. Click to View Answer ▼
Answer:
Electromagnetic induction is the phenomenon of producing an electric current in a conductor when the magnetic field linked with it changes. In a generator, a coil is rotated mechanically in a magnetic field. As the coil rotates, the magnetic flux through it changes, inducing an electric current. The direction of induced current can be determined using Fleming's right-hand rule. A generator therefore converts mechanical energy into electrical energy. In an alternating-current generator, the direction of current changes periodically, while suitable arrangements can produce direct current. Electromagnetic induction is the basic principle behind large-scale electrical power generation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 3994 Marks 12. Magnetic Effects of Electric Current Compare an electric motor and an electric generator on the basis of energy conversion and principle. Click to View Answer ▼
Answer:
An electric motor and an electric generator are closely related electromagnetic devices but perform opposite energy conversions. A motor converts electrical energy into mechanical energy. It works on the principle that a current-carrying conductor placed in a magnetic field experiences a force. A generator converts mechanical energy into electrical energy and works on electromagnetic induction, in which a changing magnetic flux induces current. Motors are used in fans, pumps, mixers and electric vehicles. Generators are used in power stations and backup systems. Thus, although both involve coils, magnets and electromagnetic effects, their input and output energy forms are reversed.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4004 Marks 12. Magnetic Effects of Electric Current Explain how the strength of the magnetic field of a solenoid can be controlled and discuss its uses. Click to View Answer ▼
Answer:
A solenoid is a long coil containing many closely spaced turns of insulated wire. When current passes through it, it produces a magnetic field similar to that of a bar magnet, with a north and south pole. The strength of the field depends on factors such as current and the number of turns per unit length. Inserting a suitable soft iron core can greatly strengthen the field because the core becomes magnetised. The strength can therefore be controlled by changing current, turns or core material. Solenoids are used to make electromagnets and in devices such as relays, electric bells and electromagnetic switches.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4014 Marks 12. Magnetic Effects of Electric Current Explain the magnetic field produced by a current-carrying straight conductor and the right-hand thumb rule Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A current-carrying conductor produces a magnetic field around itself. For a straight conductor, the field lines form concentric circles in planes perpendicular to the conductor. The strength of the field increases when current increases and decreases as the distance from the conductor increases. The direction can be determined using the right-hand thumb rule: if the thumb of the right hand points in the direction of conventional current, the curled fingers indicate the direction of magnetic field lines. This principle demonstrates the connection between electric current and magnetism and forms the basis of many electromagnetic devices This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4024 Marks 12. Magnetic Effects of Electric Current Explain the construction and working principle of an electric motor Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
An electric motor converts electrical energy into mechanical energy. Its main components include a rectangular coil placed in a magnetic field, a split-ring commutator, brushes and a battery. When current passes through the coil, the two sides experience magnetic forces in opposite directions. These forces produce a turning effect that rotates the coil. After every half rotation, the split-ring commutator reverses the current direction in the coil, keeping the torque in the same rotational direction. The motor principle is therefore based on the force experienced by a current-carrying conductor placed in a magnetic field. Motors are widely used in fans, pumps and machines A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4034 Marks 12. Magnetic Effects of Electric Current Explain electromagnetic induction and the working principle of an electric generator Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electromagnetic induction is the phenomenon of producing an electric current in a conductor when the magnetic field linked with it changes. In a generator, a coil is rotated mechanically in a magnetic field. As the coil rotates, the magnetic flux through it changes, inducing an electric current. The direction of induced current can be determined using Fleming's right-hand rule. A generator therefore converts mechanical energy into electrical energy. In an alternating-current generator, the direction of current changes periodically, while suitable arrangements can produce direct current. Electromagnetic induction is the basic principle behind large-scale electrical power generation Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4044 Marks 12. Magnetic Effects of Electric Current Compare an electric motor and an electric generator on the basis of energy conversion and principle Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An electric motor and an electric generator are closely related electromagnetic devices but perform opposite energy conversions. A motor converts electrical energy into mechanical energy. It works on the principle that a current-carrying conductor placed in a magnetic field experiences a force. A generator converts mechanical energy into electrical energy and works on electromagnetic induction, in which a changing magnetic flux induces current. Motors are used in fans, pumps, mixers and electric vehicles. Generators are used in power stations and backup systems. Thus, although both involve coils, magnets and electromagnetic effects, their input and output energy forms are reversed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4054 Marks 12. Magnetic Effects of Electric Current Explain how the strength of the magnetic field of a solenoid can be controlled and discuss its uses Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A solenoid is a long coil containing many closely spaced turns of insulated wire. When current passes through it, it produces a magnetic field similar to that of a bar magnet, with a north and south pole. The strength of the field depends on factors such as current and the number of turns per unit length. Inserting a suitable soft iron core can greatly strengthen the field because the core becomes magnetised. The strength can therefore be controlled by changing current, turns or core material. Solenoids are used to make electromagnets and in devices such as relays, electric bells and electromagnetic switches For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4064 Marks 12. Magnetic Effects of Electric Current Explain the magnetic field produced by a current-carrying straight conductor and the right-hand thumb rule Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A current-carrying conductor produces a magnetic field around itself. For a straight conductor, the field lines form concentric circles in planes perpendicular to the conductor. The strength of the field increases when current increases and decreases as the distance from the conductor increases. The direction can be determined using the right-hand thumb rule: if the thumb of the right hand points in the direction of conventional current, the curled fingers indicate the direction of magnetic field lines. This principle demonstrates the connection between electric current and magnetism and forms the basis of many electromagnetic devices This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4074 Marks 12. Magnetic Effects of Electric Current Explain the construction and working principle of an electric motor Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
An electric motor converts electrical energy into mechanical energy. Its main components include a rectangular coil placed in a magnetic field, a split-ring commutator, brushes and a battery. When current passes through the coil, the two sides experience magnetic forces in opposite directions. These forces produce a turning effect that rotates the coil. After every half rotation, the split-ring commutator reverses the current direction in the coil, keeping the torque in the same rotational direction. The motor principle is therefore based on the force experienced by a current-carrying conductor placed in a magnetic field. Motors are widely used in fans, pumps and machines A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4084 Marks 12. Magnetic Effects of Electric Current Explain electromagnetic induction and the working principle of an electric generator Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electromagnetic induction is the phenomenon of producing an electric current in a conductor when the magnetic field linked with it changes. In a generator, a coil is rotated mechanically in a magnetic field. As the coil rotates, the magnetic flux through it changes, inducing an electric current. The direction of induced current can be determined using Fleming's right-hand rule. A generator therefore converts mechanical energy into electrical energy. In an alternating-current generator, the direction of current changes periodically, while suitable arrangements can produce direct current. Electromagnetic induction is the basic principle behind large-scale electrical power generation Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4094 Marks 12. Magnetic Effects of Electric Current Compare an electric motor and an electric generator on the basis of energy conversion and principle Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An electric motor and an electric generator are closely related electromagnetic devices but perform opposite energy conversions. A motor converts electrical energy into mechanical energy. It works on the principle that a current-carrying conductor placed in a magnetic field experiences a force. A generator converts mechanical energy into electrical energy and works on electromagnetic induction, in which a changing magnetic flux induces current. Motors are used in fans, pumps, mixers and electric vehicles. Generators are used in power stations and backup systems. Thus, although both involve coils, magnets and electromagnetic effects, their input and output energy forms are reversed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4104 Marks 12. Magnetic Effects of Electric Current Explain how the strength of the magnetic field of a solenoid can be controlled and discuss its uses Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A solenoid is a long coil containing many closely spaced turns of insulated wire. When current passes through it, it produces a magnetic field similar to that of a bar magnet, with a north and south pole. The strength of the field depends on factors such as current and the number of turns per unit length. Inserting a suitable soft iron core can greatly strengthen the field because the core becomes magnetised. The strength can therefore be controlled by changing current, turns or core material. Solenoids are used to make electromagnets and in devices such as relays, electric bells and electromagnetic switches For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4114 Marks 12. Magnetic Effects of Electric Current Explain the magnetic field produced by a current-carrying straight conductor and the right-hand thumb rule Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A current-carrying conductor produces a magnetic field around itself. For a straight conductor, the field lines form concentric circles in planes perpendicular to the conductor. The strength of the field increases when current increases and decreases as the distance from the conductor increases. The direction can be determined using the right-hand thumb rule: if the thumb of the right hand points in the direction of conventional current, the curled fingers indicate the direction of magnetic field lines. This principle demonstrates the connection between electric current and magnetism and forms the basis of many electromagnetic devices This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4124 Marks 12. Magnetic Effects of Electric Current Explain the construction and working principle of an electric motor Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
An electric motor converts electrical energy into mechanical energy. Its main components include a rectangular coil placed in a magnetic field, a split-ring commutator, brushes and a battery. When current passes through the coil, the two sides experience magnetic forces in opposite directions. These forces produce a turning effect that rotates the coil. After every half rotation, the split-ring commutator reverses the current direction in the coil, keeping the torque in the same rotational direction. The motor principle is therefore based on the force experienced by a current-carrying conductor placed in a magnetic field. Motors are widely used in fans, pumps and machines A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4134 Marks 12. Magnetic Effects of Electric Current Explain electromagnetic induction and the working principle of an electric generator Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electromagnetic induction is the phenomenon of producing an electric current in a conductor when the magnetic field linked with it changes. In a generator, a coil is rotated mechanically in a magnetic field. As the coil rotates, the magnetic flux through it changes, inducing an electric current. The direction of induced current can be determined using Fleming's right-hand rule. A generator therefore converts mechanical energy into electrical energy. In an alternating-current generator, the direction of current changes periodically, while suitable arrangements can produce direct current. Electromagnetic induction is the basic principle behind large-scale electrical power generation Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4144 Marks 12. Magnetic Effects of Electric Current Compare an electric motor and an electric generator on the basis of energy conversion and principle Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An electric motor and an electric generator are closely related electromagnetic devices but perform opposite energy conversions. A motor converts electrical energy into mechanical energy. It works on the principle that a current-carrying conductor placed in a magnetic field experiences a force. A generator converts mechanical energy into electrical energy and works on electromagnetic induction, in which a changing magnetic flux induces current. Motors are used in fans, pumps, mixers and electric vehicles. Generators are used in power stations and backup systems. Thus, although both involve coils, magnets and electromagnetic effects, their input and output energy forms are reversed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4154 Marks 12. Magnetic Effects of Electric Current Explain how the strength of the magnetic field of a solenoid can be controlled and discuss its uses Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A solenoid is a long coil containing many closely spaced turns of insulated wire. When current passes through it, it produces a magnetic field similar to that of a bar magnet, with a north and south pole. The strength of the field depends on factors such as current and the number of turns per unit length. Inserting a suitable soft iron core can greatly strengthen the field because the core becomes magnetised. The strength can therefore be controlled by changing current, turns or core material. Solenoids are used to make electromagnets and in devices such as relays, electric bells and electromagnetic switches For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4164 Marks 12. Magnetic Effects of Electric Current Explain the magnetic field produced by a current-carrying straight conductor and the right-hand thumb rule Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A current-carrying conductor produces a magnetic field around itself. For a straight conductor, the field lines form concentric circles in planes perpendicular to the conductor. The strength of the field increases when current increases and decreases as the distance from the conductor increases. The direction can be determined using the right-hand thumb rule: if the thumb of the right hand points in the direction of conventional current, the curled fingers indicate the direction of magnetic field lines. This principle demonstrates the connection between electric current and magnetism and forms the basis of many electromagnetic devices This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4174 Marks 12. Magnetic Effects of Electric Current Explain the construction and working principle of an electric motor Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
An electric motor converts electrical energy into mechanical energy. Its main components include a rectangular coil placed in a magnetic field, a split-ring commutator, brushes and a battery. When current passes through the coil, the two sides experience magnetic forces in opposite directions. These forces produce a turning effect that rotates the coil. After every half rotation, the split-ring commutator reverses the current direction in the coil, keeping the torque in the same rotational direction. The motor principle is therefore based on the force experienced by a current-carrying conductor placed in a magnetic field. Motors are widely used in fans, pumps and machines A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4184 Marks 12. Magnetic Effects of Electric Current Explain electromagnetic induction and the working principle of an electric generator Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electromagnetic induction is the phenomenon of producing an electric current in a conductor when the magnetic field linked with it changes. In a generator, a coil is rotated mechanically in a magnetic field. As the coil rotates, the magnetic flux through it changes, inducing an electric current. The direction of induced current can be determined using Fleming's right-hand rule. A generator therefore converts mechanical energy into electrical energy. In an alternating-current generator, the direction of current changes periodically, while suitable arrangements can produce direct current. Electromagnetic induction is the basic principle behind large-scale electrical power generation Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4194 Marks 12. Magnetic Effects of Electric Current Compare an electric motor and an electric generator on the basis of energy conversion and principle Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An electric motor and an electric generator are closely related electromagnetic devices but perform opposite energy conversions. A motor converts electrical energy into mechanical energy. It works on the principle that a current-carrying conductor placed in a magnetic field experiences a force. A generator converts mechanical energy into electrical energy and works on electromagnetic induction, in which a changing magnetic flux induces current. Motors are used in fans, pumps, mixers and electric vehicles. Generators are used in power stations and backup systems. Thus, although both involve coils, magnets and electromagnetic effects, their input and output energy forms are reversed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4204 Marks 12. Magnetic Effects of Electric Current Explain how the strength of the magnetic field of a solenoid can be controlled and discuss its uses Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A solenoid is a long coil containing many closely spaced turns of insulated wire. When current passes through it, it produces a magnetic field similar to that of a bar magnet, with a north and south pole. The strength of the field depends on factors such as current and the number of turns per unit length. Inserting a suitable soft iron core can greatly strengthen the field because the core becomes magnetised. The strength can therefore be controlled by changing current, turns or core material. Solenoids are used to make electromagnets and in devices such as relays, electric bells and electromagnetic switches For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4214 Marks 12. Magnetic Effects of Electric Current Explain the magnetic field produced by a current-carrying straight conductor and the right-hand thumb rule Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A current-carrying conductor produces a magnetic field around itself. For a straight conductor, the field lines form concentric circles in planes perpendicular to the conductor. The strength of the field increases when current increases and decreases as the distance from the conductor increases. The direction can be determined using the right-hand thumb rule: if the thumb of the right hand points in the direction of conventional current, the curled fingers indicate the direction of magnetic field lines. This principle demonstrates the connection between electric current and magnetism and forms the basis of many electromagnetic devices This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4224 Marks 12. Magnetic Effects of Electric Current Explain the construction and working principle of an electric motor Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
An electric motor converts electrical energy into mechanical energy. Its main components include a rectangular coil placed in a magnetic field, a split-ring commutator, brushes and a battery. When current passes through the coil, the two sides experience magnetic forces in opposite directions. These forces produce a turning effect that rotates the coil. After every half rotation, the split-ring commutator reverses the current direction in the coil, keeping the torque in the same rotational direction. The motor principle is therefore based on the force experienced by a current-carrying conductor placed in a magnetic field. Motors are widely used in fans, pumps and machines A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4234 Marks 12. Magnetic Effects of Electric Current Explain electromagnetic induction and the working principle of an electric generator Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electromagnetic induction is the phenomenon of producing an electric current in a conductor when the magnetic field linked with it changes. In a generator, a coil is rotated mechanically in a magnetic field. As the coil rotates, the magnetic flux through it changes, inducing an electric current. The direction of induced current can be determined using Fleming's right-hand rule. A generator therefore converts mechanical energy into electrical energy. In an alternating-current generator, the direction of current changes periodically, while suitable arrangements can produce direct current. Electromagnetic induction is the basic principle behind large-scale electrical power generation Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4244 Marks 12. Magnetic Effects of Electric Current Compare an electric motor and an electric generator on the basis of energy conversion and principle Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An electric motor and an electric generator are closely related electromagnetic devices but perform opposite energy conversions. A motor converts electrical energy into mechanical energy. It works on the principle that a current-carrying conductor placed in a magnetic field experiences a force. A generator converts mechanical energy into electrical energy and works on electromagnetic induction, in which a changing magnetic flux induces current. Motors are used in fans, pumps, mixers and electric vehicles. Generators are used in power stations and backup systems. Thus, although both involve coils, magnets and electromagnetic effects, their input and output energy forms are reversed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4254 Marks 12. Magnetic Effects of Electric Current Explain how the strength of the magnetic field of a solenoid can be controlled and discuss its uses Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A solenoid is a long coil containing many closely spaced turns of insulated wire. When current passes through it, it produces a magnetic field similar to that of a bar magnet, with a north and south pole. The strength of the field depends on factors such as current and the number of turns per unit length. Inserting a suitable soft iron core can greatly strengthen the field because the core becomes magnetised. The strength can therefore be controlled by changing current, turns or core material. Solenoids are used to make electromagnets and in devices such as relays, electric bells and electromagnetic switches For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4264 Marks 12. Magnetic Effects of Electric Current Explain the magnetic field produced by a current-carrying straight conductor and the right-hand thumb rule Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
A current-carrying conductor produces a magnetic field around itself. For a straight conductor, the field lines form concentric circles in planes perpendicular to the conductor. The strength of the field increases when current increases and decreases as the distance from the conductor increases. The direction can be determined using the right-hand thumb rule: if the thumb of the right hand points in the direction of conventional current, the curled fingers indicate the direction of magnetic field lines. This principle demonstrates the connection between electric current and magnetism and forms the basis of many electromagnetic devices This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4274 Marks 12. Magnetic Effects of Electric Current Explain the construction and working principle of an electric motor Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
An electric motor converts electrical energy into mechanical energy. Its main components include a rectangular coil placed in a magnetic field, a split-ring commutator, brushes and a battery. When current passes through the coil, the two sides experience magnetic forces in opposite directions. These forces produce a turning effect that rotates the coil. After every half rotation, the split-ring commutator reverses the current direction in the coil, keeping the torque in the same rotational direction. The motor principle is therefore based on the force experienced by a current-carrying conductor placed in a magnetic field. Motors are widely used in fans, pumps and machines A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4284 Marks 12. Magnetic Effects of Electric Current Explain electromagnetic induction and the working principle of an electric generator Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Electromagnetic induction is the phenomenon of producing an electric current in a conductor when the magnetic field linked with it changes. In a generator, a coil is rotated mechanically in a magnetic field. As the coil rotates, the magnetic flux through it changes, inducing an electric current. The direction of induced current can be determined using Fleming's right-hand rule. A generator therefore converts mechanical energy into electrical energy. In an alternating-current generator, the direction of current changes periodically, while suitable arrangements can produce direct current. Electromagnetic induction is the basic principle behind large-scale electrical power generation Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4294 Marks 12. Magnetic Effects of Electric Current Compare an electric motor and an electric generator on the basis of energy conversion and principle Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
An electric motor and an electric generator are closely related electromagnetic devices but perform opposite energy conversions. A motor converts electrical energy into mechanical energy. It works on the principle that a current-carrying conductor placed in a magnetic field experiences a force. A generator converts mechanical energy into electrical energy and works on electromagnetic induction, in which a changing magnetic flux induces current. Motors are used in fans, pumps, mixers and electric vehicles. Generators are used in power stations and backup systems. Thus, although both involve coils, magnets and electromagnetic effects, their input and output energy forms are reversed A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4304 Marks 12. Magnetic Effects of Electric Current Explain how the strength of the magnetic field of a solenoid can be controlled and discuss its uses Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
A solenoid is a long coil containing many closely spaced turns of insulated wire. When current passes through it, it produces a magnetic field similar to that of a bar magnet, with a north and south pole. The strength of the field depends on factors such as current and the number of turns per unit length. Inserting a suitable soft iron core can greatly strengthen the field because the core becomes magnetised. The strength can therefore be controlled by changing current, turns or core material. Solenoids are used to make electromagnets and in devices such as relays, electric bells and electromagnetic switches For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4314 Marks 13. Our Environment Explain the structure of an ecosystem and the interactions among its major components. Click to View Answer ▼
Answer:
An ecosystem consists of living organisms and the non-living environment interacting with one another. Biotic components include producers, consumers and decomposers. Green plants act as producers by converting solar energy into chemical energy through photosynthesis. Consumers obtain energy by feeding on plants or other organisms. Decomposers break down dead organic matter and return nutrients to the environment. Abiotic components include air, water, soil, temperature, light and minerals. Energy flows through food chains, while matter is continuously recycled. The balance among these components is essential for ecosystem stability and sustainable functioning.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4324 Marks 13. Our Environment Explain food chains, food webs and energy transfer in an ecosystem. Click to View Answer ▼
Answer:
A food chain shows a sequence of organisms through which food and energy pass. For example, grass → grasshopper → frog → snake represents a simple food chain. A food web consists of interconnected food chains because most organisms have more than one food source or predator. At each trophic level, only a small fraction of available energy is transferred to the next level; the commonly used ecological approximation is the 10 percent law. Most energy is lost through metabolic activities and heat. Consequently, food chains are generally short. Food webs provide greater stability because they contain multiple feeding relationships.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4334 Marks 13. Our Environment Explain biological magnification and discuss why top consumers are at greater risk. Click to View Answer ▼
Answer:
Biological magnification is the increase in concentration of certain non-biodegradable toxic substances at successive trophic levels of a food chain. Such substances are not easily broken down or excreted, so they accumulate in organisms. For example, if a persistent pesticide enters water, small organisms may absorb it, fish may consume many such organisms, and birds or humans may consume the fish. The concentration can therefore become highest in top consumers. This process demonstrates why persistent pollutants can have serious ecological effects even when their initial concentration in the environment is low.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4344 Marks 13. Our Environment Explain the importance of the ozone layer and the causes and consequences of ozone depletion. Click to View Answer ▼
Answer:
The ozone layer in the upper atmosphere absorbs a significant portion of harmful ultraviolet radiation from the Sun. Excessive exposure to ultraviolet radiation can damage living organisms and increase risks to human health and ecosystems. Certain chemicals released from human activities can participate in reactions that destroy ozone molecules. Historically, chlorofluorocarbons were an important concern. Ozone depletion can increase the amount of ultraviolet radiation reaching Earth's surface. International environmental measures have reduced the use of many ozone-depleting substances. Protecting the ozone layer is therefore important for maintaining a safer environment for humans, plants and animals.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4354 Marks 13. Our Environment Differentiate biodegradable and non-biodegradable substances and explain their environmental impact. Click to View Answer ▼
Answer:
Biodegradable substances can be broken down by microorganisms into simpler substances under suitable environmental conditions. Food waste, paper and many natural materials are examples. Non-biodegradable substances resist biological decomposition and may remain in the environment for long periods. Many plastics are examples. Excessive accumulation of non-biodegradable waste can pollute soil and water, harm organisms and enter food chains. Proper waste management includes reducing unnecessary consumption, reusing materials, recycling suitable products and safely disposing of residual waste. Understanding biodegradability helps us choose environmentally responsible practices and reduce long-term pollution.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4364 Marks 13. Our Environment Explain the structure of an ecosystem and the interactions among its major components Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
An ecosystem consists of living organisms and the non-living environment interacting with one another. Biotic components include producers, consumers and decomposers. Green plants act as producers by converting solar energy into chemical energy through photosynthesis. Consumers obtain energy by feeding on plants or other organisms. Decomposers break down dead organic matter and return nutrients to the environment. Abiotic components include air, water, soil, temperature, light and minerals. Energy flows through food chains, while matter is continuously recycled. The balance among these components is essential for ecosystem stability and sustainable functioning This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4374 Marks 13. Our Environment Explain food chains, food webs and energy transfer in an ecosystem Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A food chain shows a sequence of organisms through which food and energy pass. For example, grass → grasshopper → frog → snake represents a simple food chain. A food web consists of interconnected food chains because most organisms have more than one food source or predator. At each trophic level, only a small fraction of available energy is transferred to the next level; the commonly used ecological approximation is the 10 percent law. Most energy is lost through metabolic activities and heat. Consequently, food chains are generally short. Food webs provide greater stability because they contain multiple feeding relationships A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4384 Marks 13. Our Environment Explain biological magnification and discuss why top consumers are at greater risk Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Biological magnification is the increase in concentration of certain non-biodegradable toxic substances at successive trophic levels of a food chain. Such substances are not easily broken down or excreted, so they accumulate in organisms. For example, if a persistent pesticide enters water, small organisms may absorb it, fish may consume many such organisms, and birds or humans may consume the fish. The concentration can therefore become highest in top consumers. This process demonstrates why persistent pollutants can have serious ecological effects even when their initial concentration in the environment is low Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4394 Marks 13. Our Environment Explain the importance of the ozone layer and the causes and consequences of ozone depletion Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The ozone layer in the upper atmosphere absorbs a significant portion of harmful ultraviolet radiation from the Sun. Excessive exposure to ultraviolet radiation can damage living organisms and increase risks to human health and ecosystems. Certain chemicals released from human activities can participate in reactions that destroy ozone molecules. Historically, chlorofluorocarbons were an important concern. Ozone depletion can increase the amount of ultraviolet radiation reaching Earth's surface. International environmental measures have reduced the use of many ozone-depleting substances. Protecting the ozone layer is therefore important for maintaining a safer environment for humans, plants and animals A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4404 Marks 13. Our Environment Differentiate biodegradable and non-biodegradable substances and explain their environmental impact Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Biodegradable substances can be broken down by microorganisms into simpler substances under suitable environmental conditions. Food waste, paper and many natural materials are examples. Non-biodegradable substances resist biological decomposition and may remain in the environment for long periods. Many plastics are examples. Excessive accumulation of non-biodegradable waste can pollute soil and water, harm organisms and enter food chains. Proper waste management includes reducing unnecessary consumption, reusing materials, recycling suitable products and safely disposing of residual waste. Understanding biodegradability helps us choose environmentally responsible practices and reduce long-term pollution For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4414 Marks 13. Our Environment Explain the structure of an ecosystem and the interactions among its major components Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
An ecosystem consists of living organisms and the non-living environment interacting with one another. Biotic components include producers, consumers and decomposers. Green plants act as producers by converting solar energy into chemical energy through photosynthesis. Consumers obtain energy by feeding on plants or other organisms. Decomposers break down dead organic matter and return nutrients to the environment. Abiotic components include air, water, soil, temperature, light and minerals. Energy flows through food chains, while matter is continuously recycled. The balance among these components is essential for ecosystem stability and sustainable functioning This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4424 Marks 13. Our Environment Explain food chains, food webs and energy transfer in an ecosystem Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A food chain shows a sequence of organisms through which food and energy pass. For example, grass → grasshopper → frog → snake represents a simple food chain. A food web consists of interconnected food chains because most organisms have more than one food source or predator. At each trophic level, only a small fraction of available energy is transferred to the next level; the commonly used ecological approximation is the 10 percent law. Most energy is lost through metabolic activities and heat. Consequently, food chains are generally short. Food webs provide greater stability because they contain multiple feeding relationships A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4434 Marks 13. Our Environment Explain biological magnification and discuss why top consumers are at greater risk Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Biological magnification is the increase in concentration of certain non-biodegradable toxic substances at successive trophic levels of a food chain. Such substances are not easily broken down or excreted, so they accumulate in organisms. For example, if a persistent pesticide enters water, small organisms may absorb it, fish may consume many such organisms, and birds or humans may consume the fish. The concentration can therefore become highest in top consumers. This process demonstrates why persistent pollutants can have serious ecological effects even when their initial concentration in the environment is low Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4444 Marks 13. Our Environment Explain the importance of the ozone layer and the causes and consequences of ozone depletion Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The ozone layer in the upper atmosphere absorbs a significant portion of harmful ultraviolet radiation from the Sun. Excessive exposure to ultraviolet radiation can damage living organisms and increase risks to human health and ecosystems. Certain chemicals released from human activities can participate in reactions that destroy ozone molecules. Historically, chlorofluorocarbons were an important concern. Ozone depletion can increase the amount of ultraviolet radiation reaching Earth's surface. International environmental measures have reduced the use of many ozone-depleting substances. Protecting the ozone layer is therefore important for maintaining a safer environment for humans, plants and animals A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4454 Marks 13. Our Environment Differentiate biodegradable and non-biodegradable substances and explain their environmental impact Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Biodegradable substances can be broken down by microorganisms into simpler substances under suitable environmental conditions. Food waste, paper and many natural materials are examples. Non-biodegradable substances resist biological decomposition and may remain in the environment for long periods. Many plastics are examples. Excessive accumulation of non-biodegradable waste can pollute soil and water, harm organisms and enter food chains. Proper waste management includes reducing unnecessary consumption, reusing materials, recycling suitable products and safely disposing of residual waste. Understanding biodegradability helps us choose environmentally responsible practices and reduce long-term pollution For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4464 Marks 13. Our Environment Explain the structure of an ecosystem and the interactions among its major components Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
An ecosystem consists of living organisms and the non-living environment interacting with one another. Biotic components include producers, consumers and decomposers. Green plants act as producers by converting solar energy into chemical energy through photosynthesis. Consumers obtain energy by feeding on plants or other organisms. Decomposers break down dead organic matter and return nutrients to the environment. Abiotic components include air, water, soil, temperature, light and minerals. Energy flows through food chains, while matter is continuously recycled. The balance among these components is essential for ecosystem stability and sustainable functioning This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4474 Marks 13. Our Environment Explain food chains, food webs and energy transfer in an ecosystem Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A food chain shows a sequence of organisms through which food and energy pass. For example, grass → grasshopper → frog → snake represents a simple food chain. A food web consists of interconnected food chains because most organisms have more than one food source or predator. At each trophic level, only a small fraction of available energy is transferred to the next level; the commonly used ecological approximation is the 10 percent law. Most energy is lost through metabolic activities and heat. Consequently, food chains are generally short. Food webs provide greater stability because they contain multiple feeding relationships A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4484 Marks 13. Our Environment Explain biological magnification and discuss why top consumers are at greater risk Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Biological magnification is the increase in concentration of certain non-biodegradable toxic substances at successive trophic levels of a food chain. Such substances are not easily broken down or excreted, so they accumulate in organisms. For example, if a persistent pesticide enters water, small organisms may absorb it, fish may consume many such organisms, and birds or humans may consume the fish. The concentration can therefore become highest in top consumers. This process demonstrates why persistent pollutants can have serious ecological effects even when their initial concentration in the environment is low Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4494 Marks 13. Our Environment Explain the importance of the ozone layer and the causes and consequences of ozone depletion Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The ozone layer in the upper atmosphere absorbs a significant portion of harmful ultraviolet radiation from the Sun. Excessive exposure to ultraviolet radiation can damage living organisms and increase risks to human health and ecosystems. Certain chemicals released from human activities can participate in reactions that destroy ozone molecules. Historically, chlorofluorocarbons were an important concern. Ozone depletion can increase the amount of ultraviolet radiation reaching Earth's surface. International environmental measures have reduced the use of many ozone-depleting substances. Protecting the ozone layer is therefore important for maintaining a safer environment for humans, plants and animals A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4504 Marks 13. Our Environment Differentiate biodegradable and non-biodegradable substances and explain their environmental impact Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Biodegradable substances can be broken down by microorganisms into simpler substances under suitable environmental conditions. Food waste, paper and many natural materials are examples. Non-biodegradable substances resist biological decomposition and may remain in the environment for long periods. Many plastics are examples. Excessive accumulation of non-biodegradable waste can pollute soil and water, harm organisms and enter food chains. Proper waste management includes reducing unnecessary consumption, reusing materials, recycling suitable products and safely disposing of residual waste. Understanding biodegradability helps us choose environmentally responsible practices and reduce long-term pollution For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4514 Marks 13. Our Environment Explain the structure of an ecosystem and the interactions among its major components Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
An ecosystem consists of living organisms and the non-living environment interacting with one another. Biotic components include producers, consumers and decomposers. Green plants act as producers by converting solar energy into chemical energy through photosynthesis. Consumers obtain energy by feeding on plants or other organisms. Decomposers break down dead organic matter and return nutrients to the environment. Abiotic components include air, water, soil, temperature, light and minerals. Energy flows through food chains, while matter is continuously recycled. The balance among these components is essential for ecosystem stability and sustainable functioning This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4524 Marks 13. Our Environment Explain food chains, food webs and energy transfer in an ecosystem Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A food chain shows a sequence of organisms through which food and energy pass. For example, grass → grasshopper → frog → snake represents a simple food chain. A food web consists of interconnected food chains because most organisms have more than one food source or predator. At each trophic level, only a small fraction of available energy is transferred to the next level; the commonly used ecological approximation is the 10 percent law. Most energy is lost through metabolic activities and heat. Consequently, food chains are generally short. Food webs provide greater stability because they contain multiple feeding relationships A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4534 Marks 13. Our Environment Explain biological magnification and discuss why top consumers are at greater risk Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Biological magnification is the increase in concentration of certain non-biodegradable toxic substances at successive trophic levels of a food chain. Such substances are not easily broken down or excreted, so they accumulate in organisms. For example, if a persistent pesticide enters water, small organisms may absorb it, fish may consume many such organisms, and birds or humans may consume the fish. The concentration can therefore become highest in top consumers. This process demonstrates why persistent pollutants can have serious ecological effects even when their initial concentration in the environment is low Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4544 Marks 13. Our Environment Explain the importance of the ozone layer and the causes and consequences of ozone depletion Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The ozone layer in the upper atmosphere absorbs a significant portion of harmful ultraviolet radiation from the Sun. Excessive exposure to ultraviolet radiation can damage living organisms and increase risks to human health and ecosystems. Certain chemicals released from human activities can participate in reactions that destroy ozone molecules. Historically, chlorofluorocarbons were an important concern. Ozone depletion can increase the amount of ultraviolet radiation reaching Earth's surface. International environmental measures have reduced the use of many ozone-depleting substances. Protecting the ozone layer is therefore important for maintaining a safer environment for humans, plants and animals A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4554 Marks 13. Our Environment Differentiate biodegradable and non-biodegradable substances and explain their environmental impact Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Biodegradable substances can be broken down by microorganisms into simpler substances under suitable environmental conditions. Food waste, paper and many natural materials are examples. Non-biodegradable substances resist biological decomposition and may remain in the environment for long periods. Many plastics are examples. Excessive accumulation of non-biodegradable waste can pollute soil and water, harm organisms and enter food chains. Proper waste management includes reducing unnecessary consumption, reusing materials, recycling suitable products and safely disposing of residual waste. Understanding biodegradability helps us choose environmentally responsible practices and reduce long-term pollution For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4564 Marks 13. Our Environment Explain the structure of an ecosystem and the interactions among its major components Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
An ecosystem consists of living organisms and the non-living environment interacting with one another. Biotic components include producers, consumers and decomposers. Green plants act as producers by converting solar energy into chemical energy through photosynthesis. Consumers obtain energy by feeding on plants or other organisms. Decomposers break down dead organic matter and return nutrients to the environment. Abiotic components include air, water, soil, temperature, light and minerals. Energy flows through food chains, while matter is continuously recycled. The balance among these components is essential for ecosystem stability and sustainable functioning This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4574 Marks 13. Our Environment Explain food chains, food webs and energy transfer in an ecosystem Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A food chain shows a sequence of organisms through which food and energy pass. For example, grass → grasshopper → frog → snake represents a simple food chain. A food web consists of interconnected food chains because most organisms have more than one food source or predator. At each trophic level, only a small fraction of available energy is transferred to the next level; the commonly used ecological approximation is the 10 percent law. Most energy is lost through metabolic activities and heat. Consequently, food chains are generally short. Food webs provide greater stability because they contain multiple feeding relationships A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4584 Marks 13. Our Environment Explain biological magnification and discuss why top consumers are at greater risk Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Biological magnification is the increase in concentration of certain non-biodegradable toxic substances at successive trophic levels of a food chain. Such substances are not easily broken down or excreted, so they accumulate in organisms. For example, if a persistent pesticide enters water, small organisms may absorb it, fish may consume many such organisms, and birds or humans may consume the fish. The concentration can therefore become highest in top consumers. This process demonstrates why persistent pollutants can have serious ecological effects even when their initial concentration in the environment is low Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4594 Marks 13. Our Environment Explain the importance of the ozone layer and the causes and consequences of ozone depletion Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The ozone layer in the upper atmosphere absorbs a significant portion of harmful ultraviolet radiation from the Sun. Excessive exposure to ultraviolet radiation can damage living organisms and increase risks to human health and ecosystems. Certain chemicals released from human activities can participate in reactions that destroy ozone molecules. Historically, chlorofluorocarbons were an important concern. Ozone depletion can increase the amount of ultraviolet radiation reaching Earth's surface. International environmental measures have reduced the use of many ozone-depleting substances. Protecting the ozone layer is therefore important for maintaining a safer environment for humans, plants and animals A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4604 Marks 13. Our Environment Differentiate biodegradable and non-biodegradable substances and explain their environmental impact Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Biodegradable substances can be broken down by microorganisms into simpler substances under suitable environmental conditions. Food waste, paper and many natural materials are examples. Non-biodegradable substances resist biological decomposition and may remain in the environment for long periods. Many plastics are examples. Excessive accumulation of non-biodegradable waste can pollute soil and water, harm organisms and enter food chains. Proper waste management includes reducing unnecessary consumption, reusing materials, recycling suitable products and safely disposing of residual waste. Understanding biodegradability helps us choose environmentally responsible practices and reduce long-term pollution For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4614 Marks 13. Our Environment Explain the structure of an ecosystem and the interactions among its major components Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
An ecosystem consists of living organisms and the non-living environment interacting with one another. Biotic components include producers, consumers and decomposers. Green plants act as producers by converting solar energy into chemical energy through photosynthesis. Consumers obtain energy by feeding on plants or other organisms. Decomposers break down dead organic matter and return nutrients to the environment. Abiotic components include air, water, soil, temperature, light and minerals. Energy flows through food chains, while matter is continuously recycled. The balance among these components is essential for ecosystem stability and sustainable functioning This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4624 Marks 13. Our Environment Explain food chains, food webs and energy transfer in an ecosystem Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
A food chain shows a sequence of organisms through which food and energy pass. For example, grass → grasshopper → frog → snake represents a simple food chain. A food web consists of interconnected food chains because most organisms have more than one food source or predator. At each trophic level, only a small fraction of available energy is transferred to the next level; the commonly used ecological approximation is the 10 percent law. Most energy is lost through metabolic activities and heat. Consequently, food chains are generally short. Food webs provide greater stability because they contain multiple feeding relationships A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4634 Marks 13. Our Environment Explain biological magnification and discuss why top consumers are at greater risk Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Biological magnification is the increase in concentration of certain non-biodegradable toxic substances at successive trophic levels of a food chain. Such substances are not easily broken down or excreted, so they accumulate in organisms. For example, if a persistent pesticide enters water, small organisms may absorb it, fish may consume many such organisms, and birds or humans may consume the fish. The concentration can therefore become highest in top consumers. This process demonstrates why persistent pollutants can have serious ecological effects even when their initial concentration in the environment is low Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4644 Marks 13. Our Environment Explain the importance of the ozone layer and the causes and consequences of ozone depletion Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
The ozone layer in the upper atmosphere absorbs a significant portion of harmful ultraviolet radiation from the Sun. Excessive exposure to ultraviolet radiation can damage living organisms and increase risks to human health and ecosystems. Certain chemicals released from human activities can participate in reactions that destroy ozone molecules. Historically, chlorofluorocarbons were an important concern. Ozone depletion can increase the amount of ultraviolet radiation reaching Earth's surface. International environmental measures have reduced the use of many ozone-depleting substances. Protecting the ozone layer is therefore important for maintaining a safer environment for humans, plants and animals A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4654 Marks 13. Our Environment Differentiate biodegradable and non-biodegradable substances and explain their environmental impact Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Biodegradable substances can be broken down by microorganisms into simpler substances under suitable environmental conditions. Food waste, paper and many natural materials are examples. Non-biodegradable substances resist biological decomposition and may remain in the environment for long periods. Many plastics are examples. Excessive accumulation of non-biodegradable waste can pollute soil and water, harm organisms and enter food chains. Proper waste management includes reducing unnecessary consumption, reusing materials, recycling suitable products and safely disposing of residual waste. Understanding biodegradability helps us choose environmentally responsible practices and reduce long-term pollution For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4664 Marks 14. Sustainable Management of Natural Resources Explain sustainable management of natural resources and why it is essential for future generations. Click to View Answer ▼
Answer:
Sustainable management means using natural resources carefully so that present needs are met without reducing the ability of future generations to meet their needs. Resources such as forests, water, fossil fuels and minerals are limited or require long periods to regenerate. Unsustainable extraction can cause deforestation, soil degradation, water scarcity and pollution. Sustainable practices include reducing waste, reusing materials, recycling, conserving water, protecting biodiversity and using renewable energy where possible. Local communities should also participate in resource management because they often depend directly on natural resources. Sustainable management therefore balances environmental protection, social needs and responsible economic development.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4674 Marks 14. Sustainable Management of Natural Resources Explain rainwater harvesting and discuss its importance in water conservation. Click to View Answer ▼
Answer:
Rainwater harvesting is the collection and storage of rainwater for later use or for groundwater recharge. In rooftop systems, rainwater is collected through pipes and directed to storage tanks or recharge structures after suitable filtration. It reduces dependence on groundwater and municipal supplies and can help replenish groundwater levels. In areas with seasonal rainfall, harvesting allows water to be stored for periods of scarcity. It also reduces surface runoff and soil erosion. Proper design and maintenance are necessary to prevent contamination. Thus, rainwater harvesting is a practical method of improving local water security and promoting sustainable water management.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4684 Marks 14. Sustainable Management of Natural Resources Explain the role of forests in maintaining ecological balance and supporting human communities. Click to View Answer ▼
Answer:
Forests provide many ecological and social benefits. They absorb carbon dioxide, release oxygen through photosynthesis, influence local climate and help regulate the water cycle. Tree roots hold soil and reduce erosion, while forests provide habitats for numerous plants and animals. Forest products also support the livelihoods of many communities. Excessive deforestation can lead to soil erosion, loss of biodiversity, reduced groundwater recharge and climate-related impacts. Sustainable forest management involves controlled use, regeneration, protection of wildlife and participation of local communities. Therefore, forests should be managed as living ecosystems rather than treated only as sources of timber.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4694 Marks 14. Sustainable Management of Natural Resources Discuss the advantages and environmental concerns associated with large dams. Click to View Answer ▼
Answer:
Large dams provide several benefits, including irrigation, hydroelectric power generation, water storage and flood control. They can support agriculture and supply water to cities and industries. However, large reservoirs may submerge forests and agricultural land, displace communities and disturb natural river ecosystems. They can also affect sediment transport and aquatic biodiversity. Therefore, the decision to construct a dam should consider environmental, social and economic factors. Proper rehabilitation of affected people, ecological assessment and efficient water management are essential. The objective should be to obtain necessary benefits while minimising long-term environmental and social costs.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4704 Marks 14. Sustainable Management of Natural Resources Explain the three R's—reduce, reuse and recycle—and show how they support sustainable resource management. Click to View Answer ▼
Answer:
Reduce means using fewer resources and avoiding unnecessary consumption. For example, reducing excessive packaging decreases waste and saves raw materials. Reuse means using an item again instead of discarding it, such as reusing containers or books. Recycle means processing waste materials to produce useful new products, such as recycling paper, glass and certain plastics. The three R's reduce pressure on natural resources, lower energy consumption and decrease the amount of waste sent to landfills. They also encourage responsible consumption. Applying these principles at household, school and community levels is an important step toward sustainable resource management.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4714 Marks 14. Sustainable Management of Natural Resources Explain sustainable management of natural resources and why it is essential for future generations Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Sustainable management means using natural resources carefully so that present needs are met without reducing the ability of future generations to meet their needs. Resources such as forests, water, fossil fuels and minerals are limited or require long periods to regenerate. Unsustainable extraction can cause deforestation, soil degradation, water scarcity and pollution. Sustainable practices include reducing waste, reusing materials, recycling, conserving water, protecting biodiversity and using renewable energy where possible. Local communities should also participate in resource management because they often depend directly on natural resources. Sustainable management therefore balances environmental protection, social needs and responsible economic development This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4724 Marks 14. Sustainable Management of Natural Resources Explain rainwater harvesting and discuss its importance in water conservation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Rainwater harvesting is the collection and storage of rainwater for later use or for groundwater recharge. In rooftop systems, rainwater is collected through pipes and directed to storage tanks or recharge structures after suitable filtration. It reduces dependence on groundwater and municipal supplies and can help replenish groundwater levels. In areas with seasonal rainfall, harvesting allows water to be stored for periods of scarcity. It also reduces surface runoff and soil erosion. Proper design and maintenance are necessary to prevent contamination. Thus, rainwater harvesting is a practical method of improving local water security and promoting sustainable water management A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4734 Marks 14. Sustainable Management of Natural Resources Explain the role of forests in maintaining ecological balance and supporting human communities Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Forests provide many ecological and social benefits. They absorb carbon dioxide, release oxygen through photosynthesis, influence local climate and help regulate the water cycle. Tree roots hold soil and reduce erosion, while forests provide habitats for numerous plants and animals. Forest products also support the livelihoods of many communities. Excessive deforestation can lead to soil erosion, loss of biodiversity, reduced groundwater recharge and climate-related impacts. Sustainable forest management involves controlled use, regeneration, protection of wildlife and participation of local communities. Therefore, forests should be managed as living ecosystems rather than treated only as sources of timber Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4744 Marks 14. Sustainable Management of Natural Resources Discuss the advantages and environmental concerns associated with large dams Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Large dams provide several benefits, including irrigation, hydroelectric power generation, water storage and flood control. They can support agriculture and supply water to cities and industries. However, large reservoirs may submerge forests and agricultural land, displace communities and disturb natural river ecosystems. They can also affect sediment transport and aquatic biodiversity. Therefore, the decision to construct a dam should consider environmental, social and economic factors. Proper rehabilitation of affected people, ecological assessment and efficient water management are essential. The objective should be to obtain necessary benefits while minimising long-term environmental and social costs A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4754 Marks 14. Sustainable Management of Natural Resources Explain the three R's—reduce, reuse and recycle—and show how they support sustainable resource management Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Reduce means using fewer resources and avoiding unnecessary consumption. For example, reducing excessive packaging decreases waste and saves raw materials. Reuse means using an item again instead of discarding it, such as reusing containers or books. Recycle means processing waste materials to produce useful new products, such as recycling paper, glass and certain plastics. The three R's reduce pressure on natural resources, lower energy consumption and decrease the amount of waste sent to landfills. They also encourage responsible consumption. Applying these principles at household, school and community levels is an important step toward sustainable resource management For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4764 Marks 14. Sustainable Management of Natural Resources Explain sustainable management of natural resources and why it is essential for future generations Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Sustainable management means using natural resources carefully so that present needs are met without reducing the ability of future generations to meet their needs. Resources such as forests, water, fossil fuels and minerals are limited or require long periods to regenerate. Unsustainable extraction can cause deforestation, soil degradation, water scarcity and pollution. Sustainable practices include reducing waste, reusing materials, recycling, conserving water, protecting biodiversity and using renewable energy where possible. Local communities should also participate in resource management because they often depend directly on natural resources. Sustainable management therefore balances environmental protection, social needs and responsible economic development This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4774 Marks 14. Sustainable Management of Natural Resources Explain rainwater harvesting and discuss its importance in water conservation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Rainwater harvesting is the collection and storage of rainwater for later use or for groundwater recharge. In rooftop systems, rainwater is collected through pipes and directed to storage tanks or recharge structures after suitable filtration. It reduces dependence on groundwater and municipal supplies and can help replenish groundwater levels. In areas with seasonal rainfall, harvesting allows water to be stored for periods of scarcity. It also reduces surface runoff and soil erosion. Proper design and maintenance are necessary to prevent contamination. Thus, rainwater harvesting is a practical method of improving local water security and promoting sustainable water management A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4784 Marks 14. Sustainable Management of Natural Resources Explain the role of forests in maintaining ecological balance and supporting human communities Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Forests provide many ecological and social benefits. They absorb carbon dioxide, release oxygen through photosynthesis, influence local climate and help regulate the water cycle. Tree roots hold soil and reduce erosion, while forests provide habitats for numerous plants and animals. Forest products also support the livelihoods of many communities. Excessive deforestation can lead to soil erosion, loss of biodiversity, reduced groundwater recharge and climate-related impacts. Sustainable forest management involves controlled use, regeneration, protection of wildlife and participation of local communities. Therefore, forests should be managed as living ecosystems rather than treated only as sources of timber Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4794 Marks 14. Sustainable Management of Natural Resources Discuss the advantages and environmental concerns associated with large dams Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Large dams provide several benefits, including irrigation, hydroelectric power generation, water storage and flood control. They can support agriculture and supply water to cities and industries. However, large reservoirs may submerge forests and agricultural land, displace communities and disturb natural river ecosystems. They can also affect sediment transport and aquatic biodiversity. Therefore, the decision to construct a dam should consider environmental, social and economic factors. Proper rehabilitation of affected people, ecological assessment and efficient water management are essential. The objective should be to obtain necessary benefits while minimising long-term environmental and social costs A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4804 Marks 14. Sustainable Management of Natural Resources Explain the three R's—reduce, reuse and recycle—and show how they support sustainable resource management Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Reduce means using fewer resources and avoiding unnecessary consumption. For example, reducing excessive packaging decreases waste and saves raw materials. Reuse means using an item again instead of discarding it, such as reusing containers or books. Recycle means processing waste materials to produce useful new products, such as recycling paper, glass and certain plastics. The three R's reduce pressure on natural resources, lower energy consumption and decrease the amount of waste sent to landfills. They also encourage responsible consumption. Applying these principles at household, school and community levels is an important step toward sustainable resource management For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4814 Marks 14. Sustainable Management of Natural Resources Explain sustainable management of natural resources and why it is essential for future generations Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Sustainable management means using natural resources carefully so that present needs are met without reducing the ability of future generations to meet their needs. Resources such as forests, water, fossil fuels and minerals are limited or require long periods to regenerate. Unsustainable extraction can cause deforestation, soil degradation, water scarcity and pollution. Sustainable practices include reducing waste, reusing materials, recycling, conserving water, protecting biodiversity and using renewable energy where possible. Local communities should also participate in resource management because they often depend directly on natural resources. Sustainable management therefore balances environmental protection, social needs and responsible economic development This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4824 Marks 14. Sustainable Management of Natural Resources Explain rainwater harvesting and discuss its importance in water conservation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Rainwater harvesting is the collection and storage of rainwater for later use or for groundwater recharge. In rooftop systems, rainwater is collected through pipes and directed to storage tanks or recharge structures after suitable filtration. It reduces dependence on groundwater and municipal supplies and can help replenish groundwater levels. In areas with seasonal rainfall, harvesting allows water to be stored for periods of scarcity. It also reduces surface runoff and soil erosion. Proper design and maintenance are necessary to prevent contamination. Thus, rainwater harvesting is a practical method of improving local water security and promoting sustainable water management A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4834 Marks 14. Sustainable Management of Natural Resources Explain the role of forests in maintaining ecological balance and supporting human communities Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Forests provide many ecological and social benefits. They absorb carbon dioxide, release oxygen through photosynthesis, influence local climate and help regulate the water cycle. Tree roots hold soil and reduce erosion, while forests provide habitats for numerous plants and animals. Forest products also support the livelihoods of many communities. Excessive deforestation can lead to soil erosion, loss of biodiversity, reduced groundwater recharge and climate-related impacts. Sustainable forest management involves controlled use, regeneration, protection of wildlife and participation of local communities. Therefore, forests should be managed as living ecosystems rather than treated only as sources of timber Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4844 Marks 14. Sustainable Management of Natural Resources Discuss the advantages and environmental concerns associated with large dams Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Large dams provide several benefits, including irrigation, hydroelectric power generation, water storage and flood control. They can support agriculture and supply water to cities and industries. However, large reservoirs may submerge forests and agricultural land, displace communities and disturb natural river ecosystems. They can also affect sediment transport and aquatic biodiversity. Therefore, the decision to construct a dam should consider environmental, social and economic factors. Proper rehabilitation of affected people, ecological assessment and efficient water management are essential. The objective should be to obtain necessary benefits while minimising long-term environmental and social costs A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4854 Marks 14. Sustainable Management of Natural Resources Explain the three R's—reduce, reuse and recycle—and show how they support sustainable resource management Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Reduce means using fewer resources and avoiding unnecessary consumption. For example, reducing excessive packaging decreases waste and saves raw materials. Reuse means using an item again instead of discarding it, such as reusing containers or books. Recycle means processing waste materials to produce useful new products, such as recycling paper, glass and certain plastics. The three R's reduce pressure on natural resources, lower energy consumption and decrease the amount of waste sent to landfills. They also encourage responsible consumption. Applying these principles at household, school and community levels is an important step toward sustainable resource management For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4864 Marks 14. Sustainable Management of Natural Resources Explain sustainable management of natural resources and why it is essential for future generations Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Sustainable management means using natural resources carefully so that present needs are met without reducing the ability of future generations to meet their needs. Resources such as forests, water, fossil fuels and minerals are limited or require long periods to regenerate. Unsustainable extraction can cause deforestation, soil degradation, water scarcity and pollution. Sustainable practices include reducing waste, reusing materials, recycling, conserving water, protecting biodiversity and using renewable energy where possible. Local communities should also participate in resource management because they often depend directly on natural resources. Sustainable management therefore balances environmental protection, social needs and responsible economic development This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4874 Marks 14. Sustainable Management of Natural Resources Explain rainwater harvesting and discuss its importance in water conservation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Rainwater harvesting is the collection and storage of rainwater for later use or for groundwater recharge. In rooftop systems, rainwater is collected through pipes and directed to storage tanks or recharge structures after suitable filtration. It reduces dependence on groundwater and municipal supplies and can help replenish groundwater levels. In areas with seasonal rainfall, harvesting allows water to be stored for periods of scarcity. It also reduces surface runoff and soil erosion. Proper design and maintenance are necessary to prevent contamination. Thus, rainwater harvesting is a practical method of improving local water security and promoting sustainable water management A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4884 Marks 14. Sustainable Management of Natural Resources Explain the role of forests in maintaining ecological balance and supporting human communities Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Forests provide many ecological and social benefits. They absorb carbon dioxide, release oxygen through photosynthesis, influence local climate and help regulate the water cycle. Tree roots hold soil and reduce erosion, while forests provide habitats for numerous plants and animals. Forest products also support the livelihoods of many communities. Excessive deforestation can lead to soil erosion, loss of biodiversity, reduced groundwater recharge and climate-related impacts. Sustainable forest management involves controlled use, regeneration, protection of wildlife and participation of local communities. Therefore, forests should be managed as living ecosystems rather than treated only as sources of timber Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4894 Marks 14. Sustainable Management of Natural Resources Discuss the advantages and environmental concerns associated with large dams Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Large dams provide several benefits, including irrigation, hydroelectric power generation, water storage and flood control. They can support agriculture and supply water to cities and industries. However, large reservoirs may submerge forests and agricultural land, displace communities and disturb natural river ecosystems. They can also affect sediment transport and aquatic biodiversity. Therefore, the decision to construct a dam should consider environmental, social and economic factors. Proper rehabilitation of affected people, ecological assessment and efficient water management are essential. The objective should be to obtain necessary benefits while minimising long-term environmental and social costs A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4904 Marks 14. Sustainable Management of Natural Resources Explain the three R's—reduce, reuse and recycle—and show how they support sustainable resource management Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Reduce means using fewer resources and avoiding unnecessary consumption. For example, reducing excessive packaging decreases waste and saves raw materials. Reuse means using an item again instead of discarding it, such as reusing containers or books. Recycle means processing waste materials to produce useful new products, such as recycling paper, glass and certain plastics. The three R's reduce pressure on natural resources, lower energy consumption and decrease the amount of waste sent to landfills. They also encourage responsible consumption. Applying these principles at household, school and community levels is an important step toward sustainable resource management For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4914 Marks 14. Sustainable Management of Natural Resources Explain sustainable management of natural resources and why it is essential for future generations Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Sustainable management means using natural resources carefully so that present needs are met without reducing the ability of future generations to meet their needs. Resources such as forests, water, fossil fuels and minerals are limited or require long periods to regenerate. Unsustainable extraction can cause deforestation, soil degradation, water scarcity and pollution. Sustainable practices include reducing waste, reusing materials, recycling, conserving water, protecting biodiversity and using renewable energy where possible. Local communities should also participate in resource management because they often depend directly on natural resources. Sustainable management therefore balances environmental protection, social needs and responsible economic development This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4924 Marks 14. Sustainable Management of Natural Resources Explain rainwater harvesting and discuss its importance in water conservation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Rainwater harvesting is the collection and storage of rainwater for later use or for groundwater recharge. In rooftop systems, rainwater is collected through pipes and directed to storage tanks or recharge structures after suitable filtration. It reduces dependence on groundwater and municipal supplies and can help replenish groundwater levels. In areas with seasonal rainfall, harvesting allows water to be stored for periods of scarcity. It also reduces surface runoff and soil erosion. Proper design and maintenance are necessary to prevent contamination. Thus, rainwater harvesting is a practical method of improving local water security and promoting sustainable water management A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4934 Marks 14. Sustainable Management of Natural Resources Explain the role of forests in maintaining ecological balance and supporting human communities Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Forests provide many ecological and social benefits. They absorb carbon dioxide, release oxygen through photosynthesis, influence local climate and help regulate the water cycle. Tree roots hold soil and reduce erosion, while forests provide habitats for numerous plants and animals. Forest products also support the livelihoods of many communities. Excessive deforestation can lead to soil erosion, loss of biodiversity, reduced groundwater recharge and climate-related impacts. Sustainable forest management involves controlled use, regeneration, protection of wildlife and participation of local communities. Therefore, forests should be managed as living ecosystems rather than treated only as sources of timber Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4944 Marks 14. Sustainable Management of Natural Resources Discuss the advantages and environmental concerns associated with large dams Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Large dams provide several benefits, including irrigation, hydroelectric power generation, water storage and flood control. They can support agriculture and supply water to cities and industries. However, large reservoirs may submerge forests and agricultural land, displace communities and disturb natural river ecosystems. They can also affect sediment transport and aquatic biodiversity. Therefore, the decision to construct a dam should consider environmental, social and economic factors. Proper rehabilitation of affected people, ecological assessment and efficient water management are essential. The objective should be to obtain necessary benefits while minimising long-term environmental and social costs A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4954 Marks 14. Sustainable Management of Natural Resources Explain the three R's—reduce, reuse and recycle—and show how they support sustainable resource management Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Reduce means using fewer resources and avoiding unnecessary consumption. For example, reducing excessive packaging decreases waste and saves raw materials. Reuse means using an item again instead of discarding it, such as reusing containers or books. Recycle means processing waste materials to produce useful new products, such as recycling paper, glass and certain plastics. The three R's reduce pressure on natural resources, lower energy consumption and decrease the amount of waste sent to landfills. They also encourage responsible consumption. Applying these principles at household, school and community levels is an important step toward sustainable resource management For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4964 Marks 14. Sustainable Management of Natural Resources Explain sustainable management of natural resources and why it is essential for future generations Discuss the concept critically and support your explanation with a relevant example. Click to View Answer ▼
Answer:
Sustainable management means using natural resources carefully so that present needs are met without reducing the ability of future generations to meet their needs. Resources such as forests, water, fossil fuels and minerals are limited or require long periods to regenerate. Unsustainable extraction can cause deforestation, soil degradation, water scarcity and pollution. Sustainable practices include reducing waste, reusing materials, recycling, conserving water, protecting biodiversity and using renewable energy where possible. Local communities should also participate in resource management because they often depend directly on natural resources. Sustainable management therefore balances environmental protection, social needs and responsible economic development This can be further understood by considering the concept critically and support your explanation with a relevant example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4974 Marks 14. Sustainable Management of Natural Resources Explain rainwater harvesting and discuss its importance in water conservation Explain the mechanism step by step and include an appropriate example or equation. Click to View Answer ▼
Answer:
Rainwater harvesting is the collection and storage of rainwater for later use or for groundwater recharge. In rooftop systems, rainwater is collected through pipes and directed to storage tanks or recharge structures after suitable filtration. It reduces dependence on groundwater and municipal supplies and can help replenish groundwater levels. In areas with seasonal rainfall, harvesting allows water to be stored for periods of scarcity. It also reduces surface runoff and soil erosion. Proper design and maintenance are necessary to prevent contamination. Thus, rainwater harvesting is a practical method of improving local water security and promoting sustainable water management A complete answer should explain the mechanism step by step and include an appropriate example or equation.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4984 Marks 14. Sustainable Management of Natural Resources Explain the role of forests in maintaining ecological balance and supporting human communities Analyze its importance and mention two practical applications. Click to View Answer ▼
Answer:
Forests provide many ecological and social benefits. They absorb carbon dioxide, release oxygen through photosynthesis, influence local climate and help regulate the water cycle. Tree roots hold soil and reduce erosion, while forests provide habitats for numerous plants and animals. Forest products also support the livelihoods of many communities. Excessive deforestation can lead to soil erosion, loss of biodiversity, reduced groundwater recharge and climate-related impacts. Sustainable forest management involves controlled use, regeneration, protection of wildlife and participation of local communities. Therefore, forests should be managed as living ecosystems rather than treated only as sources of timber Its importance can be analyzed by considering its importance and mention two practical applications.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 4994 Marks 14. Sustainable Management of Natural Resources Discuss the advantages and environmental concerns associated with large dams Compare the related ideas and justify the conclusion with an example. Click to View Answer ▼
Answer:
Large dams provide several benefits, including irrigation, hydroelectric power generation, water storage and flood control. They can support agriculture and supply water to cities and industries. However, large reservoirs may submerge forests and agricultural land, displace communities and disturb natural river ecosystems. They can also affect sediment transport and aquatic biodiversity. Therefore, the decision to construct a dam should consider environmental, social and economic factors. Proper rehabilitation of affected people, ecological assessment and efficient water management are essential. The objective should be to obtain necessary benefits while minimising long-term environmental and social costs A useful comparison can be made by considering the related ideas and justify the conclusion with an example.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
Question 5004 Marks 14. Sustainable Management of Natural Resources Explain the three R's—reduce, reuse and recycle—and show how they support sustainable resource management Give a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate. Click to View Answer ▼
Answer:
Reduce means using fewer resources and avoiding unnecessary consumption. For example, reducing excessive packaging decreases waste and saves raw materials. Reuse means using an item again instead of discarding it, such as reusing containers or books. Recycle means processing waste materials to produce useful new products, such as recycling paper, glass and certain plastics. The three R's reduce pressure on natural resources, lower energy consumption and decrease the amount of waste sent to landfills. They also encourage responsible consumption. Applying these principles at household, school and community levels is an important step toward sustainable resource management For a four-mark response, a detailed examination suitable for a four-mark CBSE answer, using examples where appropriate.
Exam Focus
Use correct scientific terminology. Wherever applicable, include a balanced chemical equation, labelled relationship, rule, example, comparison or practical application.
Model answer: approximately 150–180 words
