When water is heated up-to 100°C it starts boiling and changes into vapor. But we see that even after continuous supply of heat temperature does not rise above the 10°C while boiling of water.

Temperature supplied after 10°C to boiling water is used to change the water into vapor and temperature of water does not rise.

On the other hand we see that when heat is supplied to ice, temperature does not rise above the 0°C, until all ice melts. In this process also the heat supplied to ice after 0°C is used to change of ice into water and temperature of ice does not rise.

• Heat is used in these processes without rise in temperature is known as Latent Heat. The latent heat is used in change of states of matter, such as from solid to liquid or from liquid to gas without rising in temperature.
• Hence, Latent heat is the heat released or absorbed by a body during the process without change in temperature of the system. This happens while change of state of matter meaning a phase transition. Example - Melting of ice, boiling of water.

The particles of solid and liquid are bonded together with great force of attraction, because of which a matter exists in a particular state. When we supply heat to a solid or liquid, the heat is supplied without come in notice is used to break the force of attraction between particles and this heat is not used to increase the kinetic energy of particles. Since, kinetic energy of particles do not increase we do not see any rise in temperature of the system.

The word ‘latent’ is derived from the Latin word ‘Latere” which means “to lie hidden”. Joseph Black introduced the term Latent heat around 1762.