(thermodynamics) A process in which the temperature of a system is reduced without any heat being exchanged between the system and its surroundings. Source: Answers.com
Quick and dirty answer: Because the liquid that is evaporating must absorb heat in order to do so. It is much like melting ice. The ice melts because is absorbs heat. If there is no heat for it to...
Energy must be put into whatever is being evaporated (to turn int from liquid to gas). An example is when one sweats, the body cools as the sweat evaporates, because the energy for the sweat (water)...