How Does Evaporation Cause Cooling?
Liquid and Vapor Liquid evaporating from a surface has a cooling effect. And different liquids have this effect to different degrees. For example, rubbing alcohol has more of an evaporative cooling effect than does water. Alcohol is what is called a volatile liquid, meaning simply that it evaporates comparatively more quickly than water. But regardless of the liquid, the principle of evaporative cooling is the same. The idea is that in its liquid state, the substance—whether water or alcohol—has a certain heat content. Critical to this are two of the three basic phases of matter: liquid and vapor. (The solid phase is, of course, the third.) Heat When a liquid evaporates, its molecules convert from the liquid phase to the vapor phase and escape from the surface. What drives this process is heat. In order for the molecule to leave the liquid surface and escape as a vapor, it must take heat energy with it. The heat that it takes with it comes from the surface from which it evaporated.
