Editing State of matter (section)

==Phase transitions==

{{Main|Phase transitions}}

[[File:Phase change - en.svg|class=skin-invert-image|thumb|upright=1.45|This diagram shows the nomenclature for the different phase transitions.]]

A state of matter is also characterized by [[phase transitions]]. A phase transition indicates a change in structure and can be recognized by an abrupt change in properties. A distinct state of matter can be defined as any set of [[thermodynamic state|states]] distinguished from any other set of states by a [[phase transition]]. Water can be said to have several distinct solid states.<ref>
{{cite web
 |author      = M. Chaplin
 |date        = 20 August 2009
 |title       = Water phase Diagram
 |url         = https://www.lsbu.ac.uk/water/phase.html
 |website        = Water Structure and Science
 |access-date  = 23 February 2010
 |url-status=live
 |archive-url  = https://web.archive.org/web/20160303173403/https://www1.lsbu.ac.uk/water/water_phase_diagram.html
 |archive-date = 3 March 2016
 |df          = dmy-all
}}</ref> The appearance of superconductivity is associated with a phase transition, so there are [[superconductivity|superconductive]] states. Likewise, [[ferromagnetism|ferromagnetic]] states are demarcated by phase transitions and have distinctive properties.
When the change of state occurs in stages the intermediate steps are called [[mesophase]]s. Such phases have been exploited by the introduction of [[liquid crystal]] technology.<ref>
{{Cite book
 |author=D.L. Goodstein
 |date=1985
 |title=States of Matter
 |publisher=[[Dover Publications|Dover Phoenix]]
 |isbn=978-0-486-49506-4
}}</ref><ref>
{{Cite book
 |author=A.P. Sutton
 |date=1993
 |title=Electronic Structure of Materials
 |pages=10–12
 |publisher=Oxford Science Publications
 |isbn=978-0-19-851754-2
}}</ref>

[[File:Ice cubes melting in a glass.ogv|thumb|Ice cubes melting showing a change in state]]
{{Table_of_phase_transitions}}

The state or ''phase'' of a given set of matter can change depending on [[pressure]] and [[temperature]] conditions, transitioning to other phases as these conditions change to favor their existence; for example, solid transitions to liquid with an increase in temperature. Near [[absolute zero]], a substance exists as a [[solid]]. As heat is added to this substance it melts into a liquid at its [[melting point]], boils into a gas at its [[boiling point]], and if heated high enough would enter a [[plasma (physics)|plasma]] state in which the [[electrons]] are so energized that they leave their parent atoms.

Forms of matter that are not composed of molecules and are organized by different forces can also be considered different states of matter. [[Superfluids]] (like [[Fermionic condensate]]) and the [[quark–gluon plasma]] are examples.

In a chemical equation, the state of matter of the chemicals may be shown as (s) for solid, (l) for liquid, and (g) for gas. An [[aqueous solution]] is denoted (aq), for example,
:<math>\text{2 Na (s) + 2 H} _2 \text{O (l)} \rightarrow \text{H} _2 \, \text{(g) + 2 Na} ^+ \text{(aq) + 2 OH} ^- \text{(aq)}</math>
Matter in the plasma state is seldom used (if at all) in chemical equations, so there is no standard symbol to denote it. In the rare equations that plasma is used it is symbolized as (p).