Faasinvaihtoa

Faasinvaihtoa, derived from the Finnish term for phase change, refers to the transformation of matter from one state of aggregation to another, such as solid to liquid, liquid to gas, or between solid forms (allotropic transformations). These transitions are governed by thermodynamic principles, particularly free energy minimization, and occur when external conditions like temperature or pressure cross a threshold known as a phase boundary. The most familiar faasinvaihtoa include melting, boiling, sublimation, melting of ice to water, vaporization of water to steam, and the solid‐solid bainitic transformation in steel. Each transition is characterized by the absorption or release of latent heat, which can be endothermic or exothermic. First‑order phase changes involve discontinuities in entropy and volume, whereas second‑order or continuous transitions, such as the superconducting transition, show continuous changes in state variables but singularities in higher derivatives. Phase diagrams map faasinvaihtoa by illustrating the stability regions of phases in temperature–pressure space, and are essential tools in materials science, chemical engineering, and meteorology. Understanding faasinvaihtoa enables control of material properties, optimization of industrial processes, and prediction of natural phenomena such as the formation of snow crystals or the behavior of planetary cores.