Question

Why does the temperature of a substance remain constant during its melting or boiling point?

Answer 1

when any substance is at its melting point or boiling point all the energy is utilised by it to change the phase by undergoing rapid collisions between the molecules present inside the substance.and hence the temperature remains constant.

Answer 2

This is because the heat supplied is continuously used up in changing the state of the substance by overcoming the forces of attraction between the particles. This heat energy absorbed without showing any rise in temperature is called latent heat.