What process typically occurs at a defined melting point in crystalline solids?

In crystalline solids, a defined melting point corresponds to the specific temperature at which the ordered structure of the solid breaks down into a more disordered liquid state. This process is known as melting. At the melting point, the thermal energy supplied to the solid is sufficient to overcome the forces holding the molecules in place within the crystal lattice, allowing them to move freely as a liquid.

Melting is a physical change that is characteristic of crystalline materials, where they transition from solid to liquid at a specific temperature. This is different from processes like evaporation, which involves a phase change from liquid to gas, and occurs below the boiling point; condensation, which is a phase transition from gas to liquid; and sublimation, which is the transition from solid directly to gas without passing through the liquid phase. Each of these processes occurs under different conditions and is not directly related to the melting point of crystalline solids.

Thus, melting is the correct process associated with the defined melting point in crystalline solids.