How does water evaporate?
At the interface between water and air, there are a few molecules of liquid that move into the gas phase, and vice versa. At a given temperature, in a closed vessel, these two movements (evaporation and condensation) are at an equilibrium: the amount of water evaporating is equal to the amount of water condensing. The rate of evaporation is determined by temperature: the higher the temperature, the fatser molecules will enter into the gas phase. the rate of condensation is determined by pressure; the higher the pressure, the higher the rate of condensation. When the system is open (no pressure but atmospheric), the evaporation will not have a corresponding pressure increase as effect: therefore the rate of evaporation is larger than the rate of condensation, and eventually all the water will enter the gas phase. Answer originally posted in response to How does water evaporate?
