Question

(a) What is a physical change ? Give two examples of physical changes.
(b) What is a chemical change ? Give two examples of chemical changes.

Answer 1

(a) Physical change: These are changes in which no new substances are formed. These are temporary changes, which are easily reversible. The substance, which is involved in a physical change, does not lose its identity.
Examples:
(i) Water, if boiled, can be cooled and condensed.
(ii) Mixing of iron fillings with sand is a physical change because they can be separated by a magnet.

(b) Chemical change: These changes occur when a substance combines with another to form a new substance. These processes are called chemical reactions and, in general, are not reversible except by further chemical reactions.
Examples:
(i) Rusting of iron
(ii) Burning of paper