Phase transition

In physics, a phase transition is the transformation of a thermodynamic system from one phase to another. The distinguishing characteristic of a phase transition is an abrupt sudden change in one or more physical properties, in particular the heat capacity, with a small change in a thermodynamic variable such as the temperature. Examples of phase transitions are:

Related Topics:
Physics - Thermodynamic - Phase - Heat capacity - Temperature

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• The transitions between the solid, liquid, and gaseous phases (evaporation, boiling, melting, freezing, sublimation, etc.; see also vapor pressure)
• The transition between the ferromagnetic and paramagnetic phases of magnetic materials at the Curie point.
• The emergence of superconductivity in certain metals when cooled below a critical temperature.
• Quantum condensation of bosonic fluids, such as Bose-Einstein condensation and the superfluid transition in liquid helium.
• The breaking of symmetries in the laws of physics during the early history of the universe as its temperature cooled.

Phase transitions happen when the free energy of a system is non-analytic for some choice of thermodynamic variables - see phases. This non-analyticity generally stems from the interactions of an extremely large number of particles in a system, and does not appear in systems that are too small.

Related Topics:
Free energy - Non-analytic - Phases

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It's sometimes possible to change the state of a system non-adiabatically in such a way that it can be brought past a phase transition without undergoing a phase transition. The resulting state is metastable i.e. not theoretically stable, but quasistable. See superheating and supercooling and supersaturation.

Related Topics:
Adiabatic - Metastable - Superheating - Supercooling - Supersaturation

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Phase transition: Classification of phase transitions ►