What does evaporation refer to in the context of heat exchange?

In the context of heat exchange, evaporation refers specifically to the transformation of a liquid into a gas. This process occurs when molecules in the liquid gain enough energy, typically from heat, to overcome the forces that hold them together as a liquid and transition into the vapor state.

During evaporation, heat is absorbed from the surroundings, which is why this process typically has a cooling effect. This transformation does not involve direct contact, absorption of heat only, or the release of heat. Instead, the key aspect of evaporation is that it directly describes the phase change from liquid to gas. In practical terms, when water evaporates from a surface (like your skin on a hot day), it takes away heat energy, thus providing a natural cooling mechanism that is important in both biological and environmental contexts.