Question

why evaporation is called a surface phenomenon ?

Answer 1

Evaporation takes place at surface and below  the boiling point. The surface atoms or molecules gains energy from surroundings and overcome the attractions of other molecules & get to vapourise

EX: If you keep water under sunlight as the temperature increases the water molecules gets energy to breakdown the attractive forces and gets converted into vapour. 

Answer 2

Heya,

Evaporation:-
The process by which a liquid changes into vapour even below it's boiling point.

Evaporation is a surface phenomenon. Because when the surface area increases the rate of evaporation also increase to the equal level of area.

Example:-
During drying of the wet clothes, it is spread them out. It means that when spreading the wet clothes the surface area is increased thus it makes the clothes to dry faster.

Hope my answer helps you :)

Regards,
Shobana