Latent Heat

Latent Heat

The heat energy which has to be supplied to change the state of a substance is called its latent heat. Latent heat does not raise (or increase) the temperature.

Latent Heat is of Two Types

• Fusion
• Vaporization

Latent Heat of fusion (Solid to Liquid Change)

The latent heat of fusion (or melting) of a solid is the quantity of heat in joules required to convent 1 kilogram of the solid (at its melting point) to liquid, without any change in temperature.

Latent Heat of Vaporization

It is defined as heat required converting 1 mole of liquid into vapors completely at its boiling point.

Sublimation

The changing of a solid directly in to vapors on heating. And vapors’ into solid on cooling is known as sublimation. Sublimation can be represented as:

Ex:- Solids carbon dioxide

is a white solid called dry ice.

Gases Can be Liquefied by Applying Pressure and Lowering Temperature

Gases can be liquefied by applying pressure and lowering temperature.

Evaporation

The process of a liquid changing into vapour (or gas) even below its boiling point is called evaporation.

Factors Affecting Evaporation   

The evaporation of a liquid depends mainly on the following factors:

• Temperature
• Surface area
• Humidity
• Wind speed

Cooling Caused by Evaporation

The cooling caused by evaporation is based on the fact that when a liquid evaporates, it draws the latent heat of vaporization from ‘anything’ which it touches and makes it cool.