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In
physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scien ...

physics
, a state of matter is one of the distinct forms in which
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic partic ...
can exist. Four states of matter are observable in everyday life:
solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ...

solid
,
liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. Fluids are a Phase (matter), phase of matter and incl ...

liquid
,
gas Gas is one of the four fundamental states of matter (the others being solid, liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an appl ...

gas
, and
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral) or heliotrope, a mineral aggregate * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood plasma ...
. Many intermediate states are known to exist, such as
liquid crystal Liquid crystals (LCs) are a state of matter which has properties between those of conventional liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flow ...
, and some states only exist under extreme conditions, such as
Bose–Einstein condensate In condensed matter physics, a Bose–Einstein condensate (BEC) is a state of matter (also called the fifth state of matter) which is typically formed when a gas of bosons at low densities is cooled to temperature Temperature is a ...
s,
neutron-degenerate matter Degenerate matter is a highly dense state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a dail ...
, and
quark–gluon plasma Quark–gluon plasma or QGP is an interacting localized assembly of quarks and gluons at thermal (local kinetic) and (close to) chemical (abundance) equilibrium. The word ''plasma'' signals that free color charges are allowed. In a 1987 summary ...
, which only occur, respectively, in situations of extreme cold, extreme density, and extremely high energy. For a complete list of all exotic states of matter, see the
list of states of matter States of matter are distinguished by changes in the properties of matter associated with external factors like pressure and temperature. States are usually distinguished by a discontinuity in one of those properties: for example, raising the tem ...
. Historically, the distinction is made based on qualitative differences in properties. Matter in the solid state maintains a fixed
volume Volume is a scalar quantity (physics), scalar quantity expressing the amount of three-dimensional space enclosed by a closed surface. For example, the space that a substance (solid, liquid, gas, or Plasma (physics), plasma) or 3D shape occupies ...

volume
and shape, with component particles (
atoms An atom is the smallest unit of ordinary matter that forms a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance c ...

atoms
,
molecules A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atom An atom is the smallest unit of ordinary matter In ...

molecules
or
ions An ion () is an atom or molecule with a net electric charge, electrical charge. The charge of an electron is considered negative by convention and this charge is equal and opposite to charge of a proton, which is considered positive by convent ...

ions
) close together and fixed into place. Matter in the liquid state maintains a fixed volume, but has a variable shape that adapts to fit its container. Its particles are still close together but move freely. Matter in the gaseous state has both variable volume and shape, adapting both to fit its container. Its particles are neither close together nor fixed in place. Matter in the plasma state has variable volume and shape, and contains neutral atoms as well as a significant number of ions and
electrons The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has ma ...

electrons
, both of which can move around freely. The term "
phase Phase or phases may refer to: Science * State of matter, or phase, one of the distinct forms in which matter can exist *Phase (matter) In the physical sciences, a phase is a region of space (a thermodynamic system A thermodynamic system is a ...

phase
" is sometimes used as a
synonym A synonym is a word, morpheme A morpheme is the smallest meaningful lexical item in a language. A morpheme is not a word. The difference between a morpheme and a word is that a morpheme bound and free morphemes, sometimes does not stand alone, ...
for state of matter, but it is possible for a single compound to form different phases that are in the same state of matter. For example,
ice Ice is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere an ...

ice
is the solid state of water, but there are multiple
phases of ice
phases of ice
with different
crystal structure In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen ...

crystal structure
s, which are formed at different pressures and temperatures.


Four fundamental states


Solid

In a solid, constituent particles (ions, atoms, or molecules) are closely packed together. The forces between particles are so strong that the particles cannot move freely but can only vibrate. As a result, a solid has a stable, definite shape, and a definite volume. Solids can only change their shape by an outside force, as when broken or cut. In
crystalline solids A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinet ...

crystalline solids
, the particles (atoms, molecules, or ions) are packed in a regularly ordered, repeating pattern. There are various different
crystal structure In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen ...

crystal structure
s, and the same substance can have more than one structure (or solid phase). For example,
iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundance ...

iron
has a
body-centred cubic File:Kubisches_Kristallsystem.jpg, 200px, A network model of a primitive cubic system In crystallography, the cubic (or isometric) crystal system is a crystal system where the Crystal_structure#Unit_cell, unit cell is in the shape of a cube. This ...
structure at temperatures below , and a
face-centred cubic File:Kubisches_Kristallsystem.jpg, 200px, A network model of a primitive cubic system In crystallography, the cubic (or isometric) crystal system is a crystal system where the Crystal_structure#Unit_cell, unit cell is in the shape of a cube. This i ...
structure between 912 and .
Ice Ice is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere an ...

Ice
has fifteen known crystal structures, or fifteen solid phases, which exist at various temperatures and pressures.
Glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

Glass
es and other non-crystalline,
amorphous solid In condensed matter physics and materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellec ...
s without
long-range order In physics, the terms order and disorder designate the presence or absence of some symmetry or correlation in a many-particle system. In condensed matter physics, systems typically are ordered at low temperatures; upon heating, they undergo one or ...
are not
thermal equilibrium Two physical system In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motio ...

thermal equilibrium
ground states; therefore they are described below as nonclassical states of matter. Solids can be transformed into liquids by melting, and liquids can be transformed into solids by freezing. Solids can also change directly into gases through the process of sublimation, and gases can likewise change directly into solids through
deposition Deposition may refer to: * Deposition (law), taking testimony outside of court * List of deposed politicians, Deposition (politics), the removal of a person of authority from political power * Deposition (university), a widespread initiation ritual ...
.


Liquid

A liquid is a nearly incompressible
fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. Fluids are a Phase (matter), phase of matter and include liquids, Gas, gases and Plasma (physics), pl ...
that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. The volume is definite if the
temperature Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is ...

temperature
and
pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ma ...

pressure
are constant. When a solid is heated above its
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase exist in Thermodynamic equilibrium, equilibrium. ...

melting point
, it becomes liquid, given that the pressure is higher than the
triple point In thermodynamics, the triple point of a substance is the temperature and pressure at which the three Phase (matter), phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.. It is that temperature and pressure at wh ...
of the substance. Intermolecular (or interatomic or interionic) forces are still important, but the molecules have enough energy to move relative to each other and the structure is mobile. This means that the shape of a liquid is not definite but is determined by its container. The volume is usually greater than that of the corresponding solid, the best known exception being
water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts ...

water
, HO. The highest temperature at which a given liquid can exist is its
critical temperature Critical or Critically may refer to: *Critical, or critical but stable, medical states **Critical, or intensive care medicine * Critical juncture, a discontinuous change studied in the social sciences. *Critical Software, a company specializing in ...
.


Gas

A gas is a compressible fluid. Not only will a gas conform to the shape of its container but it will also expand to fill the container. In a gas, the molecules have enough
kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion (physics), motion. It is defined as the work (physics), work needed to accelerate a body of a given mass from rest to its stated velocity. Having gaine ...
so that the effect of intermolecular forces is small (or zero for an
ideal gas An ideal gas is a theoretical gas Gas is one of the four fundamental states of matter (the others being solid, liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mecha ...
), and the typical distance between neighboring molecules is much greater than the molecular size. A gas has no definite shape or volume, but occupies the entire container in which it is confined. A liquid may be converted to a gas by heating at constant pressure to the
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding enviro ...
, or else by reducing the pressure at constant temperature. At temperatures below its
critical temperature Critical or Critically may refer to: *Critical, or critical but stable, medical states **Critical, or intensive care medicine * Critical juncture, a discontinuous change studied in the social sciences. *Critical Software, a company specializing in ...
, a gas is also called a
vapor In physics, a vapor (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, America ...
, and can be liquefied by compression alone without cooling. A vapor can exist in equilibrium with a liquid (or solid), in which case the gas pressure equals the
vapor pressure 280px, The ''pistol test tube'' experiment. The tube contains alcohol and is closed with a piece of cork. By heating the alcohol, the vapors fill in the space, increasing the pressure in the tube to the point of the cork popping out. Vapor pre ...

vapor pressure
of the liquid (or solid). A supercritical fluid (SCF) is a gas whose temperature and pressure are above the critical temperature and
critical pressure In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, radiation, and physical properties of matter. The behavior of these quantities is govern ...
respectively. In this state, the distinction between liquid and gas disappears. A supercritical fluid has the physical properties of a gas, but its high density confers solvent properties in some cases, which leads to useful applications. For example,
supercritical carbon dioxide upright=1.3, Carbon dioxide pressure-temperature phase diagram Supercritical carbon dioxide (s) is a fluid state of carbon dioxide where it is held at or above its critical temperature and critical pressure. Carbon dioxide usually behaves as a ...
is used to
extract An extract is a substance made by extracting a part of a raw material A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce goods In economics Economics () ...
caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class. It is the world's most widely consumed psychoactive drug. Unlike many other psychoactive substances, it is legal and unregulated in near ...

caffeine
in the manufacture of
decaffeinated Decaffeination is the removal of caffeine from coffee, coffee beans, Cocoa bean, cocoa, tea leaves, and other caffeine-containing materials. Decaffeinated drinks contain typically 1–2% of the original caffeine content, and sometimes as much as ...
coffee.


Plasma

Like a gas, plasma does not have definite shape or volume. Unlike gases, plasmas are electrically conductive, produce magnetic fields and electric currents, and respond strongly to electromagnetic forces. Positively charged nuclei swim in a "sea" of freely-moving disassociated electrons, similar to the way such charges exist in conductive metal, where this electron "sea" allows matter in the plasma state to conduct electricity. A gas is usually converted to a plasma in one of two ways, e.g., either from a huge voltage difference between two points, or by exposing it to extremely high temperatures. Heating matter to high temperatures causes electrons to leave the atoms, resulting in the presence of free electrons. This creates a so-called partially ionised plasma. At very high temperatures, such as those present in stars, it is assumed that essentially all electrons are "free", and that a very high-energy plasma is essentially bare nuclei swimming in a sea of electrons. This forms the so-called fully ionised plasma. The plasma state is often misunderstood, and although not freely existing under normal conditions on Earth, it is quite commonly generated by either
lightning Lightning is a naturally occurring electrostatic discharge Electrostatic discharge (ESD) is the sudden flow of electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan S ...

lightning
,
electric spark An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an Ionization, ionized, Electric current, electrically conductive channel through a normally-insulating medium, often air or other gase ...
s,
fluorescent lights light. Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than t ...

fluorescent lights
,
neon lights
neon lights
or in
plasma televisions
plasma televisions
. The Sun's corona, some types of
flame A flame (from Latin ''wikt:en:flamma#Latin, flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. Very hot flames are hot enough to have ionized gaseous components of ...

flame
, and stars are all examples of illuminated matter in the plasma state.


Phase transitions

A state of matter is also characterized by
phase transitions In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they und ...
. 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
states State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper in Columbia, South Carolina, Un ...
distinguished from any other set of states by a
phase transition In chemistry, thermodynamics, and many other related fields, phase transitions (or phase changes) are the Physical process, physical processes of transition between a state of a medium, identified by some parameters, and another one, with differe ...
. Water can be said to have several distinct solid states. The appearance of superconductivity is associated with a phase transition, so there are
superconductive Superconductivity is a set of physical properties observed in certain materials where electrical resistance In electronics and electromagnetism, the electrical resistance of an object is a measure of its opposition to the flow of electric cu ...

superconductive
states. Likewise,
ferromagnetic Ferromagnetism is the basic mechanism by which certain materials (such as iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first tra ...
states are demarcated by phase transitions and have distinctive properties. When the change of state occurs in stages the intermediate steps are called
mesophaseIn chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo ...
s. Such phases have been exploited by the introduction of
liquid crystal Liquid crystals (LCs) are a state of matter which has properties between those of conventional liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flow ...
technology. The state or ''phase'' of a given set of matter can change depending on
pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ma ...

pressure
and
temperature Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is ...

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 Absolute zero is the lowest limit of the thermodynamic temperature Thermodynamic temperature is the measure of ''absolute temperature'' and is one of the principal parameters of thermodynamics. A thermodynamic temperature reading of zero deno ...
, a substance exists as a
solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ...

solid
. As heat is added to this substance it melts into a liquid at its
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase exist in Thermodynamic equilibrium, equilibrium. ...

melting point
, boils into a gas at its
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding enviro ...
, and if heated high enough would enter a
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral) or heliotrope, a mineral aggregate * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood plasma ...
state in which the
electrons The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has ma ...
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 File:Liquid helium Rollin film.jpg, The liquid helium is in the superfluid phase. A thin invisible film creeps up the inside wall of the bowl and down on the outside. A drop forms. It will fall off into the liquid helium below. This will repeat unt ...
(like
Fermionic condensate A fermionic condensate or Fermi-Dirac condensate is a superfluid File:Liquid helium Rollin film.jpg, The liquid helium is in the superfluid phase. A thin invisible film creeps up the inside wall of the bowl and down on the outside. A drop forms. ...
) and the
quark–gluon plasma Quark–gluon plasma or QGP is an interacting localized assembly of quarks and gluons at thermal (local kinetic) and (close to) chemical (abundance) equilibrium. The word ''plasma'' signals that free color charges are allowed. In a 1987 summary ...
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 An aqueous solution is a solution Image:SaltInWaterSolutionLiquid.jpg, Making a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The salt is the solute and the water the solvent. In chemistry, a solution ...
is denoted (aq). 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).


Non-classical states


Glass

Glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

Glass
is a non-crystalline or
amorphous solid In condensed matter physics and materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellec ...
material that exhibits a
glass transition The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rub ...
when heated towards the liquid state. Glasses can be made of quite different classes of materials: inorganic networks (such as window glass, made of
silicate In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they unde ...
plus additives), metallic alloys, ionic melts,
aqueous solution An aqueous solution is a solution Image:SaltInWaterSolutionLiquid.jpg, Making a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The salt is the solute and the water the solvent. In chemistry, a solution ...
s, molecular liquids, and
polymers A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of line ...

polymers
. Thermodynamically, a glass is in a
metastable state In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through ...
with respect to its crystalline counterpart. The conversion rate, however, is practically zero.


Crystals with some degree of disorder

A
plastic crystalA plastic crystal is a crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all dir ...
is a molecular solid with long-range positional order but with constituent molecules retaining rotational freedom; in an
orientational glass In solid-state physics, an orientational glass is a molecular solid in which crystalline order and disorder (physics), long-range order coexists with quenched disorder in some Degrees of freedom (mechanics), rotational degree of freedom. An orienta ...
this degree of freedom is frozen in a quenched disordered state. Similarly, in a
spin glass In condensed matter physics, a spin glass is a magnetic state characterized by randomness, besides cooperative behavior in freezing of spins at a temperature called 'freezing temperature' ''Tf''. Magnetic spins are, roughly speaking, the orien ...
magnetic disorder is frozen.


Liquid crystal states

Liquid crystal states have properties intermediate between mobile liquids and ordered solids. Generally, they are able to flow like a liquid, but exhibiting long-range order. For example, the nematic phase consists of long rod-like molecules such as
para-azoxyanisole
para-azoxyanisole
, which is nematic in the temperature range . In this state the molecules flow as in a liquid, but they all point in the same direction (within each domain) and cannot rotate freely. Like a crystalline solid, but unlike a liquid, liquid crystals react to polarized light. Other types of liquid crystals are described in the main article on these states. Several types have technological importance, for example, in
liquid crystal display display. A liquid-crystal display (LCD) is a flat panel display, flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystal Liquid crystals (LCs) are a state of matter ...
s.


Magnetically ordered

Transition metal In chemistry, the term transition metal (or transition element) has three possible definitions: * The IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations tha ...
atoms often have
magnetic moment The magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, a ...

magnetic moment
s due to the net
spin Spin or spinning may refer to: Businesses * SPIN (cable system) or South Pacific Island Network * Spin (company), an American scooter-sharing system * SPiN, a chain of table tennis lounges Computing * SPIN model checker, Gerard Holzmann's tool fo ...
of electrons that remain unpaired and do not form chemical bonds. In some solids the magnetic moments on different atoms are ordered and can form a ferromagnet, an antiferromagnet or a ferrimagnet. In a
ferromagnet Ferromagnetism is the basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished. Ferromagnetism (along with the similar effec ...
—for instance, solid
iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundance ...

iron
—the magnetic moment on each atom is aligned in the same direction (within a
magnetic domain A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moment The magnetic moment is the magnetic strength and orientation of a magnet or other obje ...
). If the domains are also aligned, the solid is a permanent
magnet Magnetic field#Magnetic field lines, Magnetic field lines of a solenoid electromagnet, which are similar to a bar magnet as illustrated below with the iron filings A magnet is a material or object that produces a magnetic field. This magnetic ...

magnet
, which is magnetic even in the absence of an external
magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each point in a subset of space. For instance, a vector field in the plane can be visualised as a collection of arrows with ...

magnetic field
. The
magnetization In classical electromagnetism, magnetization or magnetic polarization is the vector field that expresses the density The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per uni ...
disappears when the magnet is heated to the
Curie point In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior throug ...
, which for iron is . An
antiferromagnet Antiferromagnetic ordering In materials that exhibit antiferromagnetism, the magnetic moments of atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and ...

antiferromagnet
has two networks of equal and opposite magnetic moments, which cancel each other out so that the net magnetization is zero. For example, in
nickel(II) oxide Nickel is a chemical element with the Symbol (chemistry), symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and Ductility, ductile. Pure nickel, ...
(NiO), half the nickel atoms have moments aligned in one direction and half in the opposite direction. In a ferrimagnet, the two networks of magnetic moments are opposite but unequal, so that cancellation is incomplete and there is a non-zero net magnetization. An example is
magnetite Magnetite is a mineral and one of the main iron ore Iron ores are rocks and minerals from which metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, po ...

magnetite
(FeO), which contains Fe and Fe ions with different magnetic moments. A
quantum spin liquid In condensed matter physics, a quantum spin liquid is a states of matter, phase of matter that can be formed by interacting spin (physics), quantum spins in certain magnetic materials. Quantum spin liquids (QSL) are generally characterized by the ...
(QSL) is a disordered state in a system of interacting quantum spins which preserves its disorder to very low temperatures, unlike other disordered states. It is not a liquid in physical sense, but a solid whose magnetic order is inherently disordered. The name "liquid" is due to an analogy with the molecular disorder in a conventional liquid. A QSL is neither a
ferromagnet Ferromagnetism is the basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished. Ferromagnetism (along with the similar effec ...
, where magnetic domains are parallel, nor an
antiferromagnet Antiferromagnetic ordering In materials that exhibit antiferromagnetism, the magnetic moments of atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and ...

antiferromagnet
, where the magnetic domains are antiparallel; instead, the magnetic domains are randomly oriented. This can be realized e.g. by geometrically frustrated magnetic moments that cannot point uniformly parallel or antiparallel. When cooling down and settling to a state, the domain must "choose" an orientation, but if the possible states are similar in energy, one will be chosen randomly. Consequently, despite strong short-range order, there is no long-range magnetic order.


Microphase-separated

Copolymers In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained by copolymerization of two monomer species are sometimes c ...

Copolymers
can undergo microphase separation to form a diverse array of periodic nanostructures, as shown in the example of the styrene-butadiene-styrene block copolymer shown at right. Microphase separation can be understood by analogy to the phase separation between
oil An oil is any nonpolar chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can b ...

oil
and water. Due to chemical incompatibility between the blocks, block copolymers undergo a similar phase separation. However, because the blocks are
covalently bonded A covalent bond is a chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the Coulomb's law, electrostatic force of attraction bet ...
to each other, they cannot demix macroscopically as water and oil can, and so instead the blocks form nanometre-sized structures. Depending on the relative lengths of each block and the overall block topology of the polymer, many morphologies can be obtained, each its own phase of matter.
Ionic liquid (F6), a common ionic liquid. Image:Hardware-accelerated-molecular-modeling.png, Proposed structure of an imidazolium-based ionic liquid. An ionic liquid (IL) is a salt (chemistry), salt in the liquid state. In some contexts, the term has been ...
s also display microphase separation. The anion and cation are not necessarily compatible and would demix otherwise, but electric charge attraction prevents them from separating. Their anions and cations appear to diffuse within compartmentalized layers or micelles instead of freely as in a uniform liquid.


Low-temperature states


Superconductor

Superconductors are materials which have zero
electrical resistivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how strongly it resists electric current An electric current is a stream of charged particles, ...
, and therefore perfect conductivity. This is a distinct physical state which exists at low temperature, and the resistivity increases discontinuously to a finite value at a sharply-defined transition temperature for each superconductor. A superconductor also excludes all magnetic fields from its interior, a phenomenon known as the
Meissner effect Diagram of the Meissner effect. Magnetic field lines, represented as arrows, are excluded from a superconductor when it is below its critical temperature. The Meissner effect (or Meissner–Ochsenfeld effect) is the expulsion of a magnetic field ...

Meissner effect
or perfect
diamagnetism Diamagnetic materials are repelled by a magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each point in a subset of space. For instance, a vector field in th ...
.
Superconducting magnet A superconducting magnet is an electromagnet Magnetic field produced by a solenoid (coil of wire). This drawing shows a cross section through the center of the coil. The crosses are wires in which current is moving into the page; the dots ar ...
s are used as electromagnets in
magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging Medical imaging is the technique and process of imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of a ...
machines. The phenomenon of superconductivity was discovered in 1911, and for 75 years was only known in some metals and metallic alloys at temperatures below 30 K. In 1986 so-called
high-temperature superconductivity High-temperature superconductors (abbreviated high-c or HTS) are operatively defined as materials that behave as superconductors at temperatures above , the boiling point of liquid nitrogen, one of the simplest coolants in cryogenics. All m ...
was discovered in certain
ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing a nonmetallic mineral, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick. ...

ceramic
oxides, and has now been observed in temperatures as high as 164 K.


Superfluid

in a superfluid phase creeps up on the walls of the cup in a
Rollin film Image:Liquid helium Rollin film.jpg, 200px, The liquid helium is in the superfluid phase. As long as it remains superfluid, it creeps up the inside wall of the cup as a thin film. It comes down on the outside, forming a drop which will fall into the ...
, eventually dripping out from the cup. Close to absolute zero, some liquids form a second liquid state described as superfluid because it has zero
viscosity The viscosity of a fluid is a measure of its drag (physics), resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity can be ...

viscosity
(or infinite fluidity; i.e., flowing without friction). This was discovered in 1937 for
helium Helium (from el, ἥλιος, helios Helios; Homeric Greek: ), Latinized as Helius; Hyperion and Phaethon are also the names of his father and son respectively. often given the epithets Hyperion ("the one above") and Phaethon ("the shining") ...

helium
, which forms a superfluid below the lambda temperature of . In this state it will attempt to "climb" out of its container. It also has infinite
thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal c ...

thermal conductivity
so that no
temperature gradient A temperature gradient is a physical quantity A physical quantity is a physical property of a material or system that can be Quantification (science), quantified by measurement. A physical quantity can be expressed as a ''value'', which is the alge ...
can form in a superfluid. Placing a superfluid in a spinning container will result in quantized vortices. These properties are explained by the theory that the common isotope
helium-4 Helium-4 () is a stable isotope of the element helium. It is by far the more abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth. Its nucleus is identical to an alpha particle, and consists ...

helium-4
forms a
Bose–Einstein condensate In condensed matter physics, a Bose–Einstein condensate (BEC) is a state of matter (also called the fifth state of matter) which is typically formed when a gas of bosons at low densities is cooled to temperature Temperature is a ...
(see next section) in the superfluid state. More recently,
Fermionic condensate A fermionic condensate or Fermi-Dirac condensate is a superfluid File:Liquid helium Rollin film.jpg, The liquid helium is in the superfluid phase. A thin invisible film creeps up the inside wall of the bowl and down on the outside. A drop forms. ...
superfluids have been formed at even lower temperatures by the rare isotope
helium-3 Helium-3 (3He see also helion (chemistry), helion) is a light, stable isotope of helium with two protons and one neutron (the most common isotope, helium-4, having two protons and two neutrons in contrast). Other than Isotopes of hydrogen#Hydroge ...

helium-3
and by
lithium-6 Naturally occurring lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the Symbol (chemistry), symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pr ...
.


Bose–Einstein condensate

Velocity in a gas of rubidium as it is cooled: the starting material is on the left, and Bose–Einstein condensate is on the right. In 1924, Albert Einstein and Satyendra Nath Bose predicted the "Bose–Einstein condensate" (BEC), sometimes referred to as the fifth state of matter. In a BEC, matter stops behaving as independent particles, and collapses into a single quantum state that can be described with a single, uniform wavefunction. In the gas phase, the Bose–Einstein condensate remained an unverified theoretical prediction for many years. In 1995, the research groups of Eric Cornell and Carl Wieman, of JILA at the University of Colorado at Boulder, produced the first such condensate experimentally. A Bose–Einstein condensate is "colder" than a solid. It may occur when atoms have very similar (or the same) Energy level, quantum levels, at temperatures very close to
absolute zero Absolute zero is the lowest limit of the thermodynamic temperature Thermodynamic temperature is the measure of ''absolute temperature'' and is one of the principal parameters of thermodynamics. A thermodynamic temperature reading of zero deno ...
, .


Fermionic condensate

A ''fermionic condensate'' is similar to the Bose–Einstein condensate but composed of fermions. The Pauli exclusion principle prevents fermions from entering the same quantum state, but a pair of fermions can behave as a boson, and multiple such pairs can then enter the same quantum state without restriction.


Rydberg molecule

One of the
metastable state In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through ...
s of strongly non-ideal plasma are condensates of excited state, excited atoms, called Rydberg matter. These atoms can also turn into ions and electrons if they reach a certain temperature. In April 2009, ''Nature (journal), Nature'' reported the creation of Rydberg molecules from a Rydberg atom and a ground state atom, confirming that such a state of matter could exist. The experiment was performed using ultracold rubidium atoms.


Quantum Hall state

A ''quantum Hall state'' gives rise to quantized Hall voltage measured in the direction perpendicular to the current flow. A ''Quantum spin Hall effect, quantum spin Hall state'' is a theoretical phase that may pave the way for the development of electronic devices that dissipate less energy and generate less heat. This is a derivation of the Quantum Hall state of matter.


Photonic matter

Photonic matter is a phenomenon where photons interacting with a gas develop apparent mass, and can interact with each other, even forming photonic "molecules". The source of mass is the gas, which is massive. This is in contrast to photons moving in empty space, which have no rest mass, and cannot interact.


Dropleton

A "quantum fog" of electrons and holes that flow around each other and even ripple like a liquid, rather than existing as discrete pairs.


High-energy states


Degenerate matter

Under extremely high pressure, as in the cores of dead stars, ordinary matter undergoes a transition to a series of exotic states of matter collectively known as degenerate matter, which are supported mainly by quantum mechanical effects. In physics, "degenerate" refers to two states that have the same energy and are thus interchangeable. Degenerate matter is supported by the Pauli exclusion principle, which prevents two fermionic particles from occupying the same quantum state. Unlike regular plasma, degenerate plasma expands little when heated, because there are simply no momentum states left. Consequently, degenerate stars collapse into very high densities. More massive degenerate stars are smaller, because the gravitational force increases, but pressure does not increase proportionally. Degenerate matter, Electron-degenerate matter is found inside white dwarf stars. Electrons remain bound to atoms but are able to transfer to adjacent atoms. Degenerate matter, Neutron-degenerate matter is found in neutron stars. Vast gravitational pressure compresses atoms so strongly that the electrons are forced to combine with protons via inverse beta-decay, resulting in a superdense conglomeration of neutrons. Normally free neutrons outside an atomic nucleus will Free neutron decay, decay with a half life of approximately 10 minutes, but in a neutron star, the decay is overtaken by inverse decay. Cold degenerate matter is also present in planets such as Jupiter and in the even more massive brown dwarfs, which are expected to have a core with metallic hydrogen. Because of the degeneracy, more massive brown dwarfs are not significantly larger. In metals, the electrons can be modeled as a degenerate gas moving in a lattice of non-degenerate positive ions.


Quark matter

In regular cold matter, quarks, fundamental particles of nuclear matter, are confined by the strong force into hadrons that consist of 2–4 quarks, such as protons and neutrons. Quark matter or quantum chromodynamical (QCD) matter is a group of phases where the strong force is overcome and quarks are deconfined and free to move. Quark matter phases occur at extremely high densities or temperatures, and there are no known ways to produce them in equilibrium in the laboratory; in ordinary conditions, any quark matter formed immediately undergoes radioactive decay. Strange matter is a type of quark matter that is suspected to exist inside some neutron stars close to the Tolman–Oppenheimer–Volkoff limit (approximately 2–3 solar masses), although there is no direct evidence of its existence. In strange matter, part of the energy available manifests as strange quarks, a heavier analogue of the common down quark. It may be stable at lower energy states once formed, although this is not known. Quark–gluon plasma is a very high-temperature phase in which quarks become free and able to move independently, rather than being perpetually bound into particles, in a sea of gluons, subatomic particles that transmit the strong interaction, strong force that binds quarks together. This is analogous to the liberation of electrons from atoms in a plasma. This state is briefly attainable in extremely high-energy heavy ion collisions in particle accelerators, and allows scientists to observe the properties of individual quarks, and not just theorize. Quark–gluon plasma was discovered at CERN in 2000. Unlike plasma, which flows like a gas, interactions within QGP are strong and it flows like a liquid. At high densities but relatively low temperatures, quarks are theorized to form a quark liquid whose nature is presently unknown. It forms a distinct Color–flavor locking, color-flavor locked (CFL) phase at even higher densities. This phase is superconductive for color charge. These phases may occur in neutron stars but they are presently theoretical.


Color-glass condensate

Color-glass condensate is a type of matter theorized to exist in atomic nuclei traveling near the speed of light. According to Einstein's theory of relativity, a high-energy nucleus appears length contracted, or compressed, along its direction of motion. As a result, the gluons inside the nucleus appear to a stationary observer as a "gluonic wall" traveling near the speed of light. At very high energies, the density of the gluons in this wall is seen to increase greatly. Unlike the quark–gluon plasma produced in the collision of such walls, the color-glass condensate describes the walls themselves, and is an intrinsic property of the particles that can only be observed under high-energy conditions such as those at RHIC and possibly at the Large Hadron Collider as well.


Very high energy states

Various theories predict new states of matter at very high energies. An unknown state has created the baryon asymmetry in the universe, but little is known about it. In string theory, a Hagedorn temperature is predicted for superstrings at about 1030 K, where superstrings are copiously produced. At Planck temperature (1032 K), gravity becomes a significant force between individual particles. No current theory can describe these states and they cannot be produced with any foreseeable experiment. However, these states are important in cosmology because the universe may have passed through these states in the Big Bang. The gravitational singularity predicted by general relativity to exist at the center of a black hole is ''not'' a phase of matter; it is not a material object at all (although the mass-energy of matter contributed to its creation) but rather a property of spacetime. Because spacetime breaks down there, the singularity should not be thought of as a localized structure, but as a global, topological feature of spacetime. It has been argued that elementary particles are fundamentally not material, either, but are localized properties of spacetime. In quantum gravity, singularities may in fact mark transitions to a new phase of matter.


Other proposed states


Supersolid

A supersolid is a spatially ordered material (that is, a solid or crystal) with superfluid properties. Similar to a superfluid, a supersolid is able to move without friction but retains a rigid shape. Although a supersolid is a solid, it exhibits so many characteristic properties different from other solids that many argue it is another state of matter.


String-net liquid

In a string-net liquid, atoms have apparently unstable arrangement, like a liquid, but are still consistent in overall pattern, like a solid. When in a normal solid state, the atoms of matter align themselves in a grid pattern, so that the spin of any electron is the opposite of the spin of all electrons touching it. But in a string-net liquid, atoms are arranged in some pattern that requires some electrons to have neighbors with the same spin. This gives rise to curious properties, as well as supporting some unusual proposals about the fundamental conditions of the universe itself.


Superglass

A superglass is a phase of matter characterized, at the same time, by superfluidity and a frozen amorphous structure.


Arbitrary definition

Although multiple attempts have been made to create a unified account, ultimately the definitions of what states of matter exist and the point at which states change are arbitrary. Some authors have suggested that states of matter are better thought of as a spectrum between a solid and plasma instead of being rigidly defined.https://www.researchgate.net/profile/Shota-Nunomura-2/publication/7950706_Wave_Spectra_in_Solid_and_Liquid_Complex_Dusty_Plasmas/links/545cd5810cf27487b44d40ec/Wave-Spectra-in-Solid-and-Liquid-Complex-Dusty-Plasmas.pdf


See also

* Hidden states of matter * Classical element * Condensed matter physics * Cooling curve * Phase (matter) * Supercooling * Superheating


Notes and references


External links


2005-06-22, MIT News: MIT physicists create new form of matter
Citat: "... They have become the first to create a new type of matter, a gas of atoms that shows high-temperature superfluidity."

* [https://www.sciencedaily.com/releases/2004/01/040115074553.htm 2004-01-15, ScienceDaily: Probable Discovery Of A New, Supersolid, Phase Of Matter] Citat: "...We apparently have observed, for the first time, a solid material with the characteristics of a superfluid...but because all its particles are in the identical quantum state, it remains a solid even though its component particles are continually flowing..."
2004-01-29, ScienceDaily: NIST/University Of Colorado Scientists Create New Form Of Matter: A Fermionic Condensate

Short videos demonstrating of States of Matter, solids, liquids and gases by Prof. J M Murrell, University of Sussex
{{DEFAULTSORT:State Of Matter Condensed matter physics Engineering thermodynamics Phases of matter,