Check sibling questions

Classify the changes involved in the following processes as physical or chemical changes:

  1. Photosynthesis
  2. Dissolving sugar in water
  3. Burning of coal
  4. Melting of wax
  5. Beating aluminium to make aluminium foil
  6. Digestion of food

Answer:

(a) It results in the production of new substances (such as food for plants and CO2 ).

  • Hence, Photosynthesis is a chemical change.

(b) It is a temporary change, and sugar crystals can be obtained back from water through heating.

  • Hence, dissolving sugar in water is a physical change

(c) Burning is always accompanied by the evolution of heat and ligh t and is irreversible .

  • Hence, burning of coal is a chemical change

(d) Melting of wax leads to a change in the state of wax and is reversible .

  • Hence, melting of wax is a physical change.

(e) Beating aluminium leads to a change in shape but leads to no changes in the properties of aluminium.

Therefore, beating aluminium to make aluminium foil is a physical change.

(f) Digestion of food involves chemical reactions , absorption and formation of new products in the digestive system. 

Therefore, digestion of food is a chemical change.

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Economics, Accounting and English at Teachoo