Describe the cooling curve of a pure metal.

The cooling curve of a pure metal is characterized by showing constant temperature during phase changes, specifically during the transitions from liquid to solid and from solid to liquid. When a pure metal is cooled from its molten state, it reaches its melting point where it begins to solidify. During this phase change, the temperature remains constant as the thermal energy is released and the metal transitions from a liquid to a solid state. This plateau on the cooling curve signifies that heat is being removed but no temperature change occurs until the entire mass has transformed into the solid phase.

This behavior is attributed to the latent heat of fusion, which is the energy required for the phase change to take place, highlighting the unique properties of pure substances. In contrast, other options address different aspects that do not accurately describe the cooling curve of a pure metal. For example, decreasing steadily without plateaus would not account for the phase change phenomena, while suggesting that the curve is unique for each alloy overlooks that the behavior described primarily applies to pure metals. Increasing temperature during solidification misrepresents the cooling process, as the temperature cannot rise during this phase transition.