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Question
Some changes are classified as given below:
Which of the above changes are incorrectly matched?
Some changes are classified as given below:
Which of the above changes are incorrectly matched?
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Solution
The correct option is B All are correct
∙ A physical change is generally reversible. But not all physical changes are reversible.
∙ Sliced apple turning brown: Sliced apple turn brown due to its oxidation ( reaction with oxygen) resulting in the formation of new substances. A new substance is formed during this process, hence it is a chemical change. Slicing an apple involves a change in its shape and size and that can not be reversed. Hence slicing an apple is an irreversible change.
∙ Cystallisation of sugar: Crystallisation is a process by which a pure soluble substance separates out in the form of crystals from its hot solution on cooling. The process of crystallisation involves only a change in the state, i.e., from dissolved substance in the solution to its solid crystals, but the composition of the original substance remains the same. Hence crystallisation of sugar is an reversible physical change.
∙ Cooking of vegetables: The chemical composition of vegetables changes after cooking Raw vegetables cannot be obtained once cooked. Cooking of food is an examples of irreversible chemical change as this change is permanent and can’t be undone.
∙ Photosynthesis: During photosynthesis, carbon dioxide reacts with water in the presence of sunlight and chlorophyll to form oxygen and glucose. The reactants for photosynthesis are water and carbon dioxide while the products are glucose and oxygen. A new substance is formed during this process, hence it is a chemical change.
∙ Developing photographic films: The process involves the treatment of photographic films with various chemicals. The process cannot be reversed.
∙ Crumpling of paper: Crumpling of paper is physical change as only the size and shape of the paper is altered while no new substance is formed. Crumpling of paper is an reversible change.
∙ Thus, option B is the right answer.
∙ A physical change is generally reversible. But not all physical changes are reversible.
∙ Sliced apple turning brown: Sliced apple turn brown due to its oxidation ( reaction with oxygen) resulting in the formation of new substances. A new substance is formed during this process, hence it is a chemical change. Slicing an apple involves a change in its shape and size and that can not be reversed. Hence slicing an apple is an irreversible change.
∙ Cystallisation of sugar: Crystallisation is a process by which a pure soluble substance separates out in the form of crystals from its hot solution on cooling. The process of crystallisation involves only a change in the state, i.e., from dissolved substance in the solution to its solid crystals, but the composition of the original substance remains the same. Hence crystallisation of sugar is an reversible physical change.
∙ Cooking of vegetables: The chemical composition of vegetables changes after cooking Raw vegetables cannot be obtained once cooked. Cooking of food is an examples of irreversible chemical change as this change is permanent and can’t be undone.
∙ Photosynthesis: During photosynthesis, carbon dioxide reacts with water in the presence of sunlight and chlorophyll to form oxygen and glucose. The reactants for photosynthesis are water and carbon dioxide while the products are glucose and oxygen. A new substance is formed during this process, hence it is a chemical change.
∙ Developing photographic films: The process involves the treatment of photographic films with various chemicals. The process cannot be reversed.
∙ Crumpling of paper: Crumpling of paper is physical change as only the size and shape of the paper is altered while no new substance is formed. Crumpling of paper is an reversible change.
∙ Thus, option B is the right answer.
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