Question

why evaporation is directly proportional to surface area

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

Answer 2

Basically Evaporation depends upon many factors like ....
increses in temperature....
wind speed ....
Increase in surface area....
So here one of them is the increase in the surface area....
Basically when we increase the surface area .....the area of liquid expands gradually ....due to which a more and more amount of liquid comes in directly exposure of the environmental conditions .....due to which it increasingly helps in absorption of surrounding heat or latent temp....to vapourise the liquid faster and faster.......

Hope or helps u....