Question

explain why there is no rise in temperature of a substance when it undergoes a change of state though it is being continuously heated

Answer 1

There is no change or rise in temperature when a substance is heated for change in state because that energy is consumed in change of state.
Namely it's called latent heat of vaporization or latent heat of liquifiation.

Answer 2

Answer:

There is no rise in the temperature of a substance when it undergoes a change of state though heat is being supplied because heat is used to overcome inter-molecular force of attraction between the particles of the substance during a change in physical state.