College Physics III – Thermodynamics, Electricity, and Magnetism
Definition
Heat of sublimation is the energy required to change a substance from a solid to a gas without passing through the liquid phase. It is a specific type of latent heat associated with phase changes.
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Heat of sublimation combines the heat of fusion and the heat of vaporization for a substance.
It is usually measured in joules per gram (J/g) or kilojoules per mole (kJ/mol).
Sublimation occurs when molecules at the surface gain enough energy to overcome intermolecular forces and transition directly into the gas phase.
The heat of sublimation can be calculated using Hess's Law, which states that the total enthalpy change during a process is the same regardless of how many steps it takes.
Common examples of sublimation include dry ice (solid CO2) turning into carbon dioxide gas and iodine crystals turning into iodine vapor.
Review Questions
What is heat of sublimation and how is it different from heat of fusion?
How can you calculate the heat of sublimation if you know the heats of fusion and vaporization?
Provide an example where sublimation occurs naturally or in everyday life.
Related terms
Latent Heat: The amount of heat required to cause a phase change in a substance without changing its temperature.
Heat of Fusion: The energy required to change a substance from solid to liquid at its melting point.
Heat of Vaporization: The energy required to change a substance from liquid to gas at its boiling point.