Question

what is the rolr of latent heat in change of state of a substance

Answer 1

Latent heat does not raise the temperature.But the latent heat has always to be supplied to change thestate of a substance.It is called latent heat because it becomes hidden in thesubstance undergoing the change of state,and does not show its presence by raising the temperature.The latent heatwhich we supply is used 

Answer 2

Latent heat is the amount of thermal energy, per mole, that must be added to a substance to change its state from solid to liquid or liquid to gas, or the energy given off in going the other direction, in every case at constant temperature. It’s called “latent” because it’s a latent property of the substance which originates from the collective structure of the atoms or molecules, for example, ice going to water requires energy to break the intermolecular bonds keeping H2O in a solid state, and water going to steam requires still more energy to break the (weaker) liquid-state intermolecular bond