Other than heat and vibration, one factor or property that causes evaporation is what is generally known as Brownian motion. The scientist Robert Brown discovered that the molecules in water (all liquids to some extent) are always in motion. In this process they collide. The collision changes the direction of motion. So there is random motion among molecules. The molecules at the surface when kicked in the right direction escapes into air. This is evaporation. As the temperature of the liquid increases the speed and thus the energy of collision increases and thus the number of molecules escaping into air increases.
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