What is evaporation? Explain it on the basis of molecular motion.

The change of liquid into its vapour at all temperatures from its surface is called evaporation.

The inter-molecular force of attraction is lesser in liquids as compared to solids. Hence, liquid molecules can move throughout the liquid and in the process they collide with each other transferring energy between them. Molecules with higher kinetic energy reach the surface of the liquid while those with lesser kinetic energy remain inside the liquid. The higher energy molecules on the surface absorb some more heat from the surroundings to gain sufficient kinetic energy to do work against the force of attraction on them due to other molecules inside the liquid and escape out from the surface into space. These escaping molecules form the vapour of the liquid. The process continues till all the liquid evaporates.