Which term describes the energy involved in changing a substance from liquid to vapor without a temperature change?

• A. Evaporation energy
• B. Latent heat
• C. Sensible heat
• D. Kinetic energy

Answer: (B)

Latent heat is the energy absorbed or released during a phase change at a constant temperature. For liquid to vapor, this is the latent heat of vaporization. As the liquid takes in this energy, its temperature stays the same because the energy goes into breaking intermolecular forces and allowing molecules to escape into the gas phase. This is different from sensible heat, which changes temperature, and from kinetic energy, which is just the energy of motion. The term you want is latent heat (of vaporization); “evaporation energy” isn’t a standard technical term.