Question

explain how evaporation causes a cooling effect

Answer 1

a molecule that's part of a liquid will evaporate if it has enough energy (from its speed) to break through the intermolecular forces holding the liquid molecules together. Assume the total energy of the liquid remains constant, for now. If one molecule, which has significantly more energy than the average, it will take that large quantity of energy with it when it escapes the liquid phase. As a result, the molecules left behind have LESS TOTAL ENERGY than before. The AVERAGE energy per molecule has also decreased, leading to a lowering of the temperature, and a cooling effect.