1.take two dishes of different surface area's
2.pour equal amount of water in them 
3.keep them aside for two hours
4.observe it 
      we observe that water kept in larger surface evaporates faster
 1.take two dishes of equal surface.
2. put equal  amount of water in them lid for one dish in sunlight and other in a cupboard.
4.observe it
      we observe that one kept in sunlight evaporates faster.
hence it is proved that rate of evaporation of liquid depend on its surface and vapours already present.