The heat of sublimation is a physical property of substances at temperatures above their critical point, i.e., where the gas and liquid phases are not distinguishable. It is defined as the heat required to sublimate one mole of a substance at some combination of temperature and pressure, usually standard temperature and pressure (STP). The heat of sublimation is expressed in kJ/mol. The use of kJ/kg is also possible, but less customary.
