Question

Give two examples for each of the following cases:
(a) Physical changes that are reversible
(b) Physical changes that are not reversible
(c) Chemical changes

Answer 1

$\bullet$ A change in which only physical properties (shape, size or state) get altered is called a physical change. In a physical change, there is no change in the chemical composition of a substance as no new substance is formed.
$\bullet$ Some physical changes can be reversed.
For example, folding of paper and melting of ice
$\bullet$ Some physical changes can not be reversed.
For example, tearing of paper and breaking of glass
$\bullet$ In a chemical change, the chemical composition of the substance changes because of the formation of a new substance.
For example, burning of wood and rusting of iron