jäätymissulamisvaiheita

jäätymissulamisvaiheita refers to the freezing and melting transitions that occur during the solid–liquid phase change of a pure substance. The process is driven by the balance between thermal energy and the interatomic or intermolecular forces that stabilize the crystal lattice. At the freezing point, a liquid turns into a solid and the temperature remains constant until the entire mass has solidified. Conversely, at the melting point the solid absorbs heat, stays at the same temperature, and then transforms into liquid once the latent heat of fusion is supplied. The latent heat of fusion is the amount of heat per unit mass required to change the phase without changing temperature. For water, this value is 334 kJ kg−1, making ice–water transitions highly energy intensive.

Under equilibrium conditions, the freezing and melting temperatures are the same and the phase transition is reversible. In real systems, kinetic factors can produce hysteresis: supercooling, where a liquid remains below its crystallization point, or superheating, where a solid persists above its melting point. In mixtures or alloys the presence of impurities depresses the freezing point, an effect described by the Gibbs–Thomson relation. These phenomena are fundamental in meteorology, cryogenic engineering, materials science, and the food industry, where precise control of freezing and melting is essential.