Stopienie

Stopienie (Polish for "melting" or "fusion") denotes the phase transition in which a solid becomes a liquid when thermal energy overcomes the forces holding its structure. At the microscopic level, increasing temperature raises atomic or molecular vibrations until the ordered lattice breaks down and long-range positional order is lost while short-range interactions remain.

The temperature at which this transition occurs for a pure substance is the melting point, a characteristic property influenced by pressure and chemical composition. Melting requires latent heat — energy absorbed without a change in temperature — which varies between materials. Non-ideal systems such as alloys, mixtures, and amorphous solids can exhibit melting over a range of temperatures, eutectic behavior, or glass transition instead of a sharp point.

Pressure effects on melting are described by thermodynamic relations (e.g., the Clapeyron equation); for most substances increasing pressure raises the melting point, though anomalous cases like ice show the opposite. Kinetic phenomena such as supercooling and superheating occur when a material remains in a metastable solid or liquid state beyond its equilibrium melting point.

Practical contexts include metallurgy and casting, welding, material synthesis, cryogenics, and geology, where partial melting drives magmatic processes. Laboratory techniques for studying melting include differential scanning calorimetry, melting point apparatuses, and microscopy to observe structural changes. Understanding melting is fundamental to materials science, physical chemistry, and engineering applications.