Heat of sublimation

Definition

Heat of sublimation is the amount of energy required to change a substance from a solid phase directly to a gas phase without passing through the liquid phase. It is usually measured in joules per gram (J/g) or kilojoules per mole (kJ/mol).

5 Must Know Facts For Your Next Test

1. Heat of sublimation combines both the heat of fusion and the heat of vaporization.
2. It is an endothermic process, meaning it requires energy input from the surroundings.
3. Sublimation occurs under specific temperature and pressure conditions, typically low pressure and high temperature.
4. The heat of sublimation can be calculated using Hess's Law by summing the enthalpies of fusion and vaporization.
5. Typical substances that undergo sublimation include dry ice (solid CO2) and iodine.

Review Questions

• What is meant by 'heat of sublimation'?
• How does the heat of sublimation compare with heat of fusion and vaporization?
• Name two substances that commonly undergo sublimation.

Related terms

Heat of Fusion: The amount of energy required to change a substance from solid to liquid at its melting point.

Heat of Vaporization: The amount of energy required to change a substance from liquid to gas at its boiling point.

Phase Change: A transition between different states of matter, such as solid, liquid, and gas.