Latent Heat

States of matter

Conversion of states

Latent heat

The heat energy that has to be supplied to a matter to change is state is called latent heat.

Latent does not change the temperature of substance instead this temperature is used up to change the state of matter. Normally, when we supply heat to a substance its temperature increases but when the substance undergoes a change in state this supplied heat is utilized in changing its state.  Literally the word “latent” means hidden or concealed. Latent heat means the hidden heat because it is not visible in form of temperature change by rising the temperature, but this heat is utilized to change the state.

As discussed earlier, every substance solid or liquid has some force of attraction between its particles which hold them together. When the substance changes its state ( from solid to liquid, from liquid to gas) it has to break these attractive forces and so that the particles can move.

Why latent heat only change the state but not the temperature?

Basically, when heat is provided some heat break the attractive force and some heat is utilized in increasing the kinetic energy of particles. Latent heat is used to break the attractive force between particles and not to increase the kinetic energy so the state change but not the temperature.

There are two types of latent heat:

1.      Latent heat of fusion

2.      Latent heat of vaporisation

Latent heat of fusion: It is the heat energy used in converting a substance from solid state to liquid state.

Latent heat of vaporisation: It is the heat energy used in converting a substance from liquid state to gaseous state.