Editing Phase transition (section)

===Mixtures===
[[File:Binary phase diagram of NiTI (phase and temperature).JPG|class=skin-invert-image|thumb|250px|A binary phase diagram showing the most stable chemical compounds of [[titanium]] and [[nickel]] at different [[mixing ratio]]s and [[temperature]]s.]]

Phase transitions involving [[Solution (chemistry)|solution]]s and [[mixture]]s are more complicated than transitions involving a single compound. While chemically pure compounds exhibit a single temperature [[melting point]] between solid and liquid phases, mixtures can either have a single melting point, known as [[congruent melting]], or they have different [[liquidus and solidus|liquidus and solidus temperatures]] resulting in a temperature span where solid and liquid coexist in equilibrium. This is often the case in [[solid solution]]s, where the two components are isostructural.

There are also a number of phase transitions involving three phases: a [[eutectic]] transformation, in which a two-component single-phase liquid is cooled and transforms into two solid phases. The same process, but beginning with a solid instead of a liquid is called a [[eutectoid]] transformation. A [[peritectic]] transformation, in which a two-component single-phase solid is heated and transforms into a solid phase and a liquid phase. A [[peritectoid]] reaction is a peritectoid reaction, except involving only solid phases. A [[monotectic]] reaction consists of change from a liquid and to a combination of a solid and a second liquid, where the two liquids display a [[miscibility gap]].<ref>{{cite book | last1=Askeland | first1=Donald R. | last2=Haddleton | first2=Frank | last3=Green | first3=Phil | last4=Robertson | first4=Howard | title=The Science and Engineering of Materials | date=1996 | isbn=978-0-412-53910-7 | page=286| publisher=Chapman & Hall }}</ref>

Separation into multiple phases can occur via [[spinodal decomposition]], in which a single phase is cooled and separates into two different compositions.

Non-equilibrium mixtures can occur, such as in [[supersaturation]].