The process by which a solid changes into its liquid state at a certain fixed temperature by the absorption of heat is called

• A. Liquefaction
• B. Solidification
• C. Fusion
• D. Vaporization

Answer: (C)

Melting, also called fusion, is the process where a solid absorbs heat and becomes a liquid at a fixed temperature—the melting point. During this change, the temperature stays the same because the added energy goes into breaking the orderly forces holding the particles in the solid, which is the latent heat of fusion. Once the solid has melted, further heat will raise the liquid’s temperature. The other terms refer to different direction changes: solid to liquid is melting/fusion, liquid to solid is solidification, and liquid to gas is vaporization. Liquefaction is not the standard term for the solid–to–liquid transition.