Question

Assertion (A): A substance on heating undergoes (i) a rise in its temperature (ii) a change in its phase without change in its temperature.

Reason (R): In first case, average kinetic energy of molecules increases while in the second case, average potential energy of molecules increases.

Options

• Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

• Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).

• Assertion (A) is false, but Reason (R) is true.

• Assertion (A) is true, but Reason (R) is false.

Answer 1

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Explanation:

When heat is supplied to a substance, first its temperature rises; this increases the average kinetic energy of the molecules. At the melting point, further heat changes the phase without changing the temperature; this energy increases the average potential energy of the molecules. Thus, R correctly explains A.