Question

Why does the temperature of a substance remain constant during the change of state ?

Answer 1

All substances change their state by gaining or loosing heat equal to their latent heat. On gaining heat kinetic energy of molecules increases and vice versa. During the change in state of matter, heat being absorbed or released, is utilized for bringing about a change in kinetic energy of molecules and not for rising or loosing the temperature. Therefore, the temperature of a substance remains constant during change in state.