Melting involves which change and energy transfer?

Melting involves which change and energy transfer?

• A. Solid to liquid; energy absorbed.
• B. Solid to gas; energy released.
• C. Liquid to solid; energy absorbed.
• D. Gas to liquid; energy absorbed.

Answer: (A)

When a solid melts, its particles gain enough energy to break some of the strong interactions that hold them in a fixed position, letting them flow as a liquid. This requires energy input, so melting is an endothermic process—the energy absorbed goes into changing the phase, not increasing temperature. At the melting point, the temperature remains the same while solid becomes liquid because the added energy is used for the phase change itself. The term for this energy is latent heat of fusion. So, melting is a change from solid to liquid with energy absorbed. (In contrast, solid to gas would be sublimation and also absorbs energy, while liquid to solid is freezing and releases energy, and gas to liquid is condensation, which also releases energy.)

When a solid melts, its particles gain enough energy to break some of the strong interactions that hold them in a fixed position, letting them flow as a liquid. This requires energy input, so melting is an endothermic process—the energy absorbed goes into changing the phase, not increasing temperature. At the melting point, the temperature remains the same while solid becomes liquid because the added energy is used for the phase change itself. The term for this energy is latent heat of fusion.

So, melting is a change from solid to liquid with energy absorbed. (In contrast, solid to gas would be sublimation and also absorbs energy, while liquid to solid is freezing and releases energy, and gas to liquid is condensation, which also releases energy.)