The heat of sublimation is the heat that is absorbed to transform a substance from its solid state to its vapor. In common usage, the heat of sublimation is used in place of the more precise term the enthalpy of sublimation, which has the symbol ()H_sub. The enthalpy of sublimation is the heat of sublimation for vaporizing one mole of the solid substance under three specific conditions: (1) the pressure remains constant, (2) the only possible work that occurs is expansion against the atmosphere (so-called P()V work) and (3) the temperature remains constant during the process. A heat of sublimation for a substance is only valid for conversion of the pure solid to the pure gaseous state of the substance.

Relatively few substances sublime at or near atmospheric pressure. Some examples of those that do sublime readily are carbon dioxide and iodine. Most substances are...