The standard enthalpy change of sublimation, ΔHsub o, is the change in enthalpy when one mole of a substance in the gaseous state is formed from the same substance in its solid state, without going through the liquid state, under standard conditions.
The process of sublimation is always endothermic, e.g.
The standard enthalpy change of sublimation is greater than that of vaporisation and hence greater than that of fusion. The standard enthalpy change of deposition of a substance, ΔHdep o, is the negative value of the standard enthalpy change of sublimation of that substance.
