Latent heat is the energy absorbed or released during a state change without a temperature change. Which two processes are associated with latent heat?

• A. Fusion and Vaporization
• B. Freezing and Condensation
• C. Sublimation and Deposition
• D. Melting and Freezing

Answer: (A)

Latent heat is the energy that must be added or removed to change a substance from one phase to another without changing its temperature. When a solid melts into a liquid, heat is absorbed to break the rigid structure—this is the latent heat of fusion. When a liquid boils into a gas, more heat is absorbed to overcome intermolecular forces and fully separate the molecules—this is the latent heat of vaporization. These two processes are the classic examples because they show energy input driving phase changes at a constant temperature.

Freezing and condensation also involve latent heat, but they are the reverse processes where energy is released as a substance changes from liquid to solid or from gas to liquid. Sublimation and deposition involve latent heat as well (solid to gas and gas to solid), but the standard teaching highlights fusion and vaporization as the primary pair associated with latent heat.