What happens during incongruent melting?

Incongruent melting refers to a specific process where a solid compound does not melt into a single liquid phase that retains the original composition of the solid. Instead, during incongruent melting, the compound decomposes into different solid and liquid phases, with the liquid phase being different in composition from the original solid. This means that rather than forming just one homogeneous liquid, the solid breaks down into its components, leading to the formation of one or more distinct solid phases alongside a liquid phase.

This phenomenon often occurs in certain types of materials, such as certain salts and intermetallic compounds, where the melting behavior is linked to the stability of different phases and a phase diagram indicative of their interactions. In contrast, terms such as melting into a single liquid phase or solidifying without a change in composition describe other melting processes that do not involve the complexity of incongruent melting.