Question

Classify the following processes into physical or chemical changes:

(i) Beating of aluminium metal to make aluminium foil.
(ii) Digestion of food.
(iii) Cutting of a log of wood into pieces.
(iv) Rusting of iron.

Answer 1

In a physical change, there is no change in the chemical composition of a substance, only a change in physical appearance and properties occurs.
Whereas, in a chemical change, the chemical composition of the substance changes because of the formation of a new substance.

$\bullet$ In the given examples, beating of aluminium metal to make aluminium foil and cutting of a log of wood into pieces are physical changes as there is no change in their composition.
$\bullet$ Digestion of food is a chemical change as the food breaks down and forms new substance inside the stomach.
$\bullet$ Rusting of iron is a chemical change as a reddish-brown flaky layer (rust) is formed on its surface when it is left in air.