Which term describes the energy required for a substance to change from a solid to a liquid at its melting point without a change in temperature?

• A. Heat
• B. Heat Capacity
• C. Latent Heat of Fusion
• D. Latent Heat of Vaporization

Answer: (C)

This question tests understanding of latent heat during a phase change. At the melting point, adding energy doesn't raise the temperature; instead, the energy goes into breaking the forces that hold the solid together so it can become a liquid. This specific energy per unit mass is the latent heat of fusion. It can be expressed as q = mLf, where Lf is the latent heat of fusion.

In contrast, heat is the general energy transferred due to a temperature difference, not specifically tied to a phase change. Heat capacity describes how much energy is needed to raise a substance’s temperature by one degree. Latent heat of vaporization refers to the energy required for a liquid to become a gas at the boiling point, a different phase transition.