Physics
Answer
Due to weak inter-molecular force of attraction the molecules of a liquid move freely inside it. 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. Thus, evaporation of the liquid happens only from the surface of the liquid. Hence, Evaporation is a surface phenomenon.
Related Questions
Do all the molecules of a liquid take part in evaporation? If not, explain your answer.
No heat is supplied to a liquid during evaporation. How does then the liquid change into its vapour?
Why is cooling produced when a liquid evaporates.
Give reason for the increase in rate of evaporation of a liquid when:
(a) air is blown above the liquid.
(b) surface area of liquid is increased.
(c) temperature of liquid is increased.