What is evaporation Related: NCERT Solutions - Is Matter Around Us Pu...
Evaporation
The process of liquid changing into vapours even below its boiling point is called as evaporation.
Some particles in a liquid always have more kinetic energy than the others.So,even when a liquid is well below its boiling point ,some of its particles have enough energy to break the forces of attraction between the particles and escape from the surface of the liquid in the form of vapours.Thus,the fast moving particles of a liquid are constantly escaping from the liquid to form vapour.
Factors affecting evaporation
1)Temperature
The rate of evaporation increases on increasing temperature of the liquid.When the temperature of a liquid is increased by heating it,more particles of the liquid get enough kinetic energy to go into vapour state.This increases the rate of evaporation.
2)Surface Area
The rate of evaporation increases on increasing the surface area of the liquid.
For Ex:IF the same liquid is kept in a test tube and in a china dish,then the liquid kept in the china dish evaporates more rapidly.
We spread out the washed clothes while drying to increase their surface area for rapid evaporation of water present in them.
3)Humidity of air
The amount of water vapours present in air is called humidity.
When the amount of water vapours present in the air is small it is called dry air.
When the amount of water vapours present in air is large it appears to be damp.
When the humidity of air is low,then the rate of evaporation is high,and water evaporates more readily.
When the humidity of air is high,then the rate of evaporation is low.and water evaporates very slowly.
4)Wind Speed
The rate of evaporation of a liquid increases with the increasing wind speed.
When the speed of wind increases,the particles of water vapours move away with the wind,decreasing the amount of water vapours in the surrounding.This increases the rate of evaporation of water.The washed wet clothes dry more quickly on a windy day because evaporation is faster due to the high speed of the wind.