Question

Define a periodic change. Is rusting a periodic change?

Answer 1

Changes that are repeated at regular intervals of time are called periodic changes. Examples of periodic changes are:

(i) Change of day and night.

(ii) Change of seasons - spring, summer, autumn, and winter.

Rusting is defined as the brown flaky substance developed on the surface of iron when iron comes in contact with atmospheric oxygen and water vapor.

Rusting is not a periodic change because we cannot bring back the original iron by reversing the conditions. That's why rusting is not a periodic change. It is a chemical change.