In a liquid, molecules are free to move and have a range of energies. Molecules in the liquid surface typically have higher energies than molecules deeper in the liquid. Energetic molecules may escape from the liquid, There is a force attracting molecules back into the liquid, but the most energetic molecules have enough energy to overcome this force and escape the influence of the liquid completely. The molecules that escape the liquid completely have evaporated. As the temperature of the liquid increase, the average energy of the liquid molecules increase and a higher fraction of gas molecules have enough energy to evaporate.
When evaporation takes place, the average energy of the molecules in the liquid falls. Energy and temperature are directly related, so if the average energy of the liquid molecules falls, so does the temperature. When this happens on your skin, you feel a cooling effect. Evaporation can be increased by:
o Increasing temperature so that more particles have enough energy to escape. o Increasing the surface area of the liquid so more molecules are close to the surface.
o Reduce humidity level so that air has more capacity to absorb liquid. o Blow air across the liquid surface so that liquid molecules above the liquid are less likely to reenter the liquid.