Editing Phase (matter) (section)

== Types of phases ==
[[File:Iron carbon phase diagram.svg|class=skin-invert-image|thumb|left|350px|Iron-carbon [[phase diagram]], showing the conditions necessary to form different phases]]
Distinct phases may be described as different [[state of matter|states of matter]] such as [[gas]], [[liquid]], [[solid]], [[plasma (physics)|plasma]] or [[Bose–Einstein condensate]]. Useful [[mesophase]]s between solid and liquid form other states of matter.

Distinct phases may also exist within a given state of matter. As shown in the diagram for iron alloys, several phases exist for both the solid and liquid states. Phases may also be differentiated based on [[solubility]] as in polar (hydrophilic) or non-polar (hydrophobic). A mixture of water (a polar liquid) and oil (a non-polar liquid) will spontaneously separate into two phases. Water has a very low [[solubility]] (is insoluble) in oil, and oil has a low solubility in water. Solubility is the maximum amount of a solute that can dissolve in a solvent before the solute ceases to dissolve and remains in a separate phase. A mixture can separate into more than two liquid phases and the concept of phase separation extends to solids, i.e., solids can form [[solid solution]]s or crystallize into distinct crystal phases. Metal pairs that are mutually soluble can form [[alloy]]s, whereas metal pairs that are mutually insoluble cannot.

As many as [[multiphasic liquid|eight immiscible liquid phases]] have been observed.{{efn|One such system is, from the top: [[mineral oil]], [[silicone oil]], [[water]], [[aniline]], [[perfluoro(dimethylcyclohexane)]], [[white phosphorus]], [[gallium]], and [[mercury (element)|mercury]]. The system remains indefinitely separated at {{val|45|u=°C}}, where gallium and phosphorus are in the molten state. From {{cite book|author=Reichardt, C.|date=2006|title=Solvents and Solvent Effects in Organic Chemistry|pages=9–10|publisher=[[Wiley-VCH]]|isbn=978-3-527-60567-5}}}} Mutually immiscible liquid phases are formed from water (aqueous phase), hydrophobic organic solvents, [[perfluorocarbon]]s ([[organofluorine chemistry#Fluorous phases|fluorous phase]]), silicones, several different metals, and also from molten phosphorus. Not all organic solvents are completely miscible, e.g. a mixture of [[ethylene glycol]] and [[toluene]] may separate into two distinct organic phases.{{efn|This phenomenon can be used to help with catalyst recycling in [[Heck reaction|Heck vinylation]]. See {{cite journal|author=Bhanage, B.M.|display-authors=etal|date=1998|title=Comparison of activity and selectivity of various metal-TPPTS complex catalysts in ethylene glycol — toluene biphasic Heck vinylation reactions of iodobenzene|journal=[[Tetrahedron Letters]]|volume=39|issue=51|pages=9509–9512|doi=10.1016/S0040-4039(98)02225-4}}}}

Phases do not need to macroscopically separate spontaneously. [[Emulsion]]s and [[colloid]]s are examples of immiscible phase pair combinations that do not physically separate.
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