First-order phase transition

A first-order phase transition is a change in a material's state that occurs suddenly, rather than gradually. Examples include melting ice into water or boiling water into steam. During this transition, certain physical properties, like density or enthalpy, change sharply. There is usually a specific temperature or pressure at which the transition occurs, and both phases can coexist at this point. It involves the breaking or forming of bonds, leading to a distinct change in the material's structure and behavior.