Which energy change occurs during melting?

Which energy change occurs during melting?

• A. Melting releases energy
• B. Freezing requires energy
• C. Melting requires energy
• D. Condensation releases energy

Answer: (C)

During melting, energy must be added to a solid to overcome the forces that hold its particles in a fixed arrangement. This input of energy allows the particles to move past one another and form a liquid. Because energy is absorbed in this phase change, melting is endothermic, and the amount of energy required per amount of substance is the latent heat of fusion. At the melting point, heat goes into changing the state rather than raising temperature, so the temperature stays constant until all the solid has melted, after which heating can raise the temperature again. The other ideas don’t fit this specific process: freezing releases energy as the solid forms bonds, and condensation also releases energy when a gas becomes a liquid.

During melting, energy must be added to a solid to overcome the forces that hold its particles in a fixed arrangement. This input of energy allows the particles to move past one another and form a liquid. Because energy is absorbed in this phase change, melting is endothermic, and the amount of energy required per amount of substance is the latent heat of fusion. At the melting point, heat goes into changing the state rather than raising temperature, so the temperature stays constant until all the solid has melted, after which heating can raise the temperature again.

The other ideas don’t fit this specific process: freezing releases energy as the solid forms bonds, and condensation also releases energy when a gas becomes a liquid.