Which statement correctly identifies the phase change involved in latent heat of fusion?

• A. Between liquid and gas.
• B. Between solid and liquid.
• C. Between gas and liquid.
• D. Between solid and gas.

Answer: (B)

The phase change involved is between a solid and a liquid. Latent heat of fusion is the energy needed to melt a solid at its melting point, with no change in temperature during the change. For example, ice at 0°C absorbs heat to become liquid water still at 0°C; the energy goes into breaking the solid’s structure so it can flow as a liquid. Once all the solid has melted, further heat then raises the temperature of the liquid. Other phase changes involve solid–gas (sublimation) or gas–liquid (condensation/vaporization), not fusion.