Question

Define the following
(A) Specific latent heat of fusion
(B) Specific latent heat of vaporization

Answer 1

Hint: The heat energy required to change one kilo of ice from solid to liquid state is known as the specific latent heat of fusion. The heat required to change one kilo of water in the liquid state to a vapor state without a change in temperature is known as specific latent heat of vaporization.

Complete solution:
When solid changes to liquid at atmospheric pressure at its melting point, the amount of heat energy released is known as the latent heat of fusion. The specific latent heat of a substance is the amount of energy required to change the state of one kilo of the substance without change in its temperature.

The latent heat of vaporization or evaporation is the heat given to some mass to convert it from the liquid to the vapor phase. Similarly, latent heat of vaporization or evaporation is the heat that has to be given to one kilo mass of material to convert it from the liquid to the vapor phase without changing its temperature.

Additional information: Consider the example, a pot of water is boiling, the temperature remains at ${100^0}C\,(212{\,^0}F)$ until the last drop evaporates, because all the heat being added to the liquid is absorbed as the latent heat of vaporization and then carried away by the escaping vapour molecules.

Note: There are three phases of substances: Solid, liquid and gaseous. Similarly, there are three types of latent heat; latent heat of fusion, latent heat of vaporization and latent heat of sublimation. Latent heat of sublimation is the heat given when a substance gets directly converted from solid to gaseous.