(a) During photosynthesis, green plants prepare glucose with the help of carbon dioxide from the air and water from the soil. Is photosynthesis a physical change or a chemical change? Justify your answer.
(b) Copper sulphate is a blue coloured chemical. When it is heated, the blue colour disappears and it turns white. After is cools, if a few drops of water are put into the test tube, the copper sulphate turns blue again. Is this a physical or a chemical change?

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Solution

(a) Photosynthesis is a chemical change. During photosynthesis, a new substance glucose is formed from raw materials like carbon dioxide and water. This process is irreversible.
(b) Heating of copper sulphate is a physical change. It does not change the properties of copper sulphate and only evaporates water present in it. It is a reversible change.

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