Phase (matter)

In the physical sciences, a phase is a region of space (a thermodynamic system), throughout which all physical properties of a material are essentially uniform.[1][2]:86[3]:3 Examples of physical properties include density, index of refraction, magnetization and chemical composition. A simple description is that a phase is a region of material that is chemically uniform, physically distinct, and (often) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air is a third phase over the ice and water. The glass of the jar is another separate phase. (See state of matter § Glass)

The term phase is sometimes used as a synonym for state of matter, but there can be several immiscible phases of the same state of matter. Also, the term phase is sometimes used to refer to a set of equilibrium states demarcated in terms of state variables such as pressure and temperature by a phase boundary on a phase diagram. Because phase boundaries relate to changes in the organization of matter, such as a change from liquid to solid or a more subtle change from one crystal structure to another, this latter usage is similar to the use of "phase" as a synonym for state of matter. However, the state of matter and phase diagram usages are not commensurate with the formal definition given above and the intended meaning must be determined in part from the context in which the term is used.

Argon ice 1
A small piece of rapidly melting argon ice shows the transition from solid to liquid.

Types of phases

Steel pd
Iron-carbon phase diagram, showing the conditions necessary to form different phases

Distinct phases may be described as different states of matter such as gas, liquid, solid, plasma or Bose–Einstein condensate. Useful mesophases 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 solutions or crystallize into distinct crystal phases. Metal pairs that are mutually soluble can form alloys, whereas metal pairs that are mutually insoluble cannot.

As many as eight immiscible liquid phases have been observed.[a] Mutually immiscible liquid phases are formed from water (aqueous phase), hydrophobic organic solvents, perfluorocarbons (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.[b]

Phases do not need to macroscopically separate spontaneously. Emulsions and colloids are examples of immiscible phase pair combinations that do not physically separate.

Phase equilibrium

Left to equilibration, many compositions will form a uniform single phase, but depending on the temperature and pressure even a single substance may separate into two or more distinct phases. Within each phase, the properties are uniform but between the two phases properties differ.

Water in a closed jar with an air space over it forms a two phase system. Most of the water is in the liquid phase, where it is held by the mutual attraction of water molecules. Even at equilibrium molecules are constantly in motion and, once in a while, a molecule in the liquid phase gains enough kinetic energy to break away from the liquid phase and enter the gas phase. Likewise, every once in a while a vapor molecule collides with the liquid surface and condenses into the liquid. At equilibrium, evaporation and condensation processes exactly balance and there is no net change in the volume of either phase.

At room temperature and pressure, the water jar reaches equilibrium when the air over the water has a humidity of about 3%. This percentage increases as the temperature goes up. At 100 °C and atmospheric pressure, equilibrium is not reached until the air is 100% water. If the liquid is heated a little over 100 °C, the transition from liquid to gas will occur not only at the surface, but throughout the liquid volume: the water boils.

Number of phases

A typical phase diagram for a single-component material, exhibiting solid, liquid and gaseous phases. The solid green line shows the usual shape of the liquid–solid phase line. The dotted green line shows the anomalous behavior of water when the pressure increases. The triple point and the critical point are shown as red dots.

For a given composition, only certain phases are possible at a given temperature and pressure. The number and type of phases that will form is hard to predict and is usually determined by experiment. The results of such experiments can be plotted in phase diagrams.

The phase diagram shown here is for a single component system. In this simple system, which phases that are possible depends only on pressure and temperature. The markings show points where two or more phases can co-exist in equilibrium. At temperatures and pressures away from the markings, there will be only one phase at equilibrium.

In the diagram, the blue line marking the boundary between liquid and gas does not continue indefinitely, but terminates at a point called the critical point. As the temperature and pressure approach the critical point, the properties of the liquid and gas become progressively more similar. At the critical point, the liquid and gas become indistinguishable. Above the critical point, there are no longer separate liquid and gas phases: there is only a generic fluid phase referred to as a supercritical fluid. In water, the critical point occurs at around 647 K (374 °C or 705 °F) and 22.064 MPa.

An unusual feature of the water phase diagram is that the solid–liquid phase line (illustrated by the dotted green line) has a negative slope. For most substances, the slope is positive as exemplified by the dark green line. This unusual feature of water is related to ice having a lower density than liquid water. Increasing the pressure drives the water into the higher density phase, which causes melting.

Another interesting though not unusual feature of the phase diagram is the point where the solid–liquid phase line meets the liquid–gas phase line. The intersection is referred to as the triple point. At the triple point, all three phases can coexist.

Experimentally, the phase lines are relatively easy to map due to the interdependence of temperature and pressure that develops when multiple phases forms. See Gibbs' phase rule. Consider a test apparatus consisting of a closed and well insulated cylinder equipped with a piston. By charging the right amount of water and applying heat, the system can be brought to any point in the gas region of the phase diagram. If the piston is slowly lowered, the system will trace a curve of increasing temperature and pressure within the gas region of the phase diagram. At the point where gas begins to condense to liquid, the direction of the temperature and pressure curve will abruptly change to trace along the phase line until all of the water has condensed.

Interfacial phenomena

Between two phases in equilibrium there is a narrow region where the properties are not that of either phase. Although this region may be very thin, it can have significant and easily observable effects, such as causing a liquid to exhibit surface tension. In mixtures, some components may preferentially move toward the interface. In terms of modeling, describing, or understanding the behavior of a particular system, it may be efficacious to treat the interfacial region as a separate phase.

Crystal phases

A single material may have several distinct solid states capable of forming separate phases. Water is a well-known example of such a material. For example, water ice is ordinarily found in the hexagonal form ice Ih, but can also exist as the cubic ice Ic, the rhombohedral ice II, and many other forms. Polymorphism is the ability of a solid to exist in more than one crystal form. For pure chemical elements, polymorphism is known as allotropy. For example, diamond, graphite, and fullerenes are different allotropes of carbon.

Phase transitions

When a substance undergoes a phase transition (changes from one state of matter to another) it usually either takes up or releases energy. For example, when water evaporates, the increase in kinetic energy as the evaporating molecules escape the attractive forces of the liquid is reflected in a decrease in temperature. The energy required to induce the phase transition is taken from the internal thermal energy of the water, which cools the liquid to a lower temperature; hence evaporation is useful for cooling. See Enthalpy of vaporization. The reverse process, condensation, releases heat. The heat energy, or enthalpy, associated with a solid to liquid transition is the enthalpy of fusion and that associated with a solid to gas transition is the enthalpy of sublimation.

Phases out of equilibrium

While phases of matter are traditionally defined for systems in thermal equilibrium, work on quantum many-body localized (MBL) systems has provided a framework for defining phases out of equilibrium. MBL phases never reach thermal equilibrium, and can allow for new forms of order disallowed in equilibrium via a phenomenon known as localization protected quantum order. The transitions between different MBL phases and between MBL and thermalizing phases are novel dynamical phase transitions whose properties are active areas of research.

See also


  1. ^ One such system is, from the top: mineral oil, silicone oil, water, aniline, perfluoro(dimethylcyclohexane), white phosphorus, gallium, and mercury. The system remains indefinitely separated at 45 °C, where gallium and phosphorus are in the molten state. From Reichardt, C. (2006). Solvents and Solvent Effects in Organic Chemistry. Wiley-VCH. pp. 9–10. ISBN 978-3-527-60567-5.
  2. ^ This phenomenon can be used to help with catalyst recycling in Heck vinylation. See Bhanage, B.M.; et al. (1998). "Comparison of activity and selectivity of various metal-TPPTS complex catalysts in ethylene glycol — toluene biphasic Heck vinylation reactions of iodobenzene". Tetrahedron Letters. 39 (51): 9509–9512. doi:10.1016/S0040-4039(98)02225-4.


  1. ^ Modell, Michael; Robert C. Reid (1974). Thermodynamics and Its Applications. Englewood Cliffs, NJ: Prentice-Hall. ISBN 978-0-13-914861-3.
  2. ^ Enrico Fermi (25 April 2012). Thermodynamics. Courier Corporation. ISBN 978-0-486-13485-7.
  3. ^ Clement John Adkins (14 July 1983). Equilibrium Thermodynamics. Cambridge University Press. ISBN 978-0-521-27456-2.

External links


Biphasic, meaning having two phases, may refer to:

Phase (matter), in the physical sciences, a biphasic system, e.g. one involving liquid water and steam

Biphasic sleep, a nap or siesta in addition to the usual sleep episode at night

Phase (pharmacology)

Biphasic disease

Biphasic formulations of oral contraceptive pills

Glossary of civil engineering

Most of the terms listed in Wikipedia glossaries are already defined and explained within Wikipedia itself. However, glossaries like this one are useful for looking up, comparing and reviewing large numbers of terms together. You can help enhance this page by adding new terms or writing definitions for existing ones.

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Glossary of engineering

Most of the terms listed in Wikipedia glossaries are already defined and explained within Wikipedia itself. However, glossaries like this one are useful for looking up, comparing and reviewing large numbers of terms together. You can help enhance this page by adding new terms or writing definitions for existing ones.

This glossary of engineering terms is a list of definitions about the major concepts of engineering. Please see the bottom of the page for glossaries of specific fields of engineering.

Glossary of physics

This glossary of physics is a list of definitions of terms and concepts relevant to physics, its sub-disciplines, and related fields, including mechanics, materials science, nuclear physics, particle physics, and thermodynamics.

For more inclusive glossaries concerning related fields of science and technology, see Glossary of chemistry terms, Glossary of astronomy, Glossary of areas of mathematics, and Glossary of engineering.

Glossary of structural engineering

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Josef Zezulka

Josef Zezulka (1912–1992) (sometimes translated as Joseph Zezulka) was a Czech philosopher, healer and the founder of the biotronics discipline. He is the author of many philosophical works. BYTÍ - EXISTENCE - A Philosophy for Life is his most famous work. The work encompasses specific topics such as the birth of space and its life, evolution of a being, karma, vegetarianism and life energetics.

Nanotechnology in fiction

The use of nanotechnology in fiction has attracted scholarly attention. The first use of the distinguishing concepts of nanotechnology was "There's Plenty of Room at the Bottom", a talk given by physicist Richard Feynman in 1959. K. Eric Drexler's 1986 book Engines of Creation introduced the general public to the concept of nanotechnology. Since then, nanotechnology has been used frequently in a diverse range of fiction, often as a justification for unusual or far-fetched occurrences featured in speculative fiction.

Polar ice cap

A polar ice cap or polar cap is a high-latitude region of a planet, dwarf planet, or natural satellite that is covered in ice.There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land; only that it must be a body of solid phase matter in the polar region. This causes the term "polar ice cap" to be something of a misnomer, as the term ice cap itself is applied more narrowly to bodies that are over land, and cover less than 50,000 km2: larger bodies are referred to as ice sheets.

The composition of the ice will vary. For example, Earth's polar caps are mainly water ice, whereas Mars's polar ice caps are a mixture of solid carbon dioxide and water ice.

Polar ice caps form because high-latitude regions receive less energy in the form of solar radiation from the Sun than equatorial regions, resulting in lower surface temperatures.

Earth's polar caps have changed dramatically over the last 12,000 years. Seasonal variations of the ice caps takes place due to varied solar energy absorption as the planet or moon revolves around the Sun. Additionally, in geologic time scales, the ice caps may grow or shrink due to climate variation.

Relational theory

In physics and philosophy, a relational theory (or relationism) is a framework to understand reality or a physical system in such a way that the positions and other properties of objects are only meaningful relative to other objects. In a relational spacetime theory, space does not exist unless there are objects in it; nor does time exist without events. The relational view proposes that space is contained in objects and that an object represents within itself relationships to other objects. Space can be defined through the relations among the objects that it contains considering their variations through time. The alternative spatial theory is an absolute theory in which the space exists independently of any objects that can be immersed in it.The relational point of view was advocated in physics by Gottfried Wilhelm Leibniz and Ernst Mach (in his Mach's principle). It was rejected by Isaac Newton in his successful description of classical physics. Although Albert Einstein was impressed by Mach's principle, he did not fully incorporate it into his general theory of relativity. Several attempts have been made to formulate a full Machian theory, but most physicists think that none have so far succeeded. For example, see Brans–Dicke theory.

Relational quantum mechanics and a relational approach to quantum physics have been independently developed, in analogy with Einstein's special relativity of space and time. Relationist physicists such as John Baez and Carlo Rovelli have criticised the leading unified theory of gravity and quantum mechanics, string theory, as retaining absolute space. Some prefer a developing theory of gravity, loop quantum gravity for its 'backgroundlessness'.

A recent synthesis of relational theory, called R-theory, continuing the work of the mathematical biologist Robert Rosen (who developed "Relational Biology" and "Relational Complexity" as theories of life () takes a position between the above views. Rosen's theory differed from other relational views in defining fundamental relations in nature (as opposed to merely epistemic relations we might discuss) as information transfers between natural systems and their organization (as expressed in models). R-theory extends the idea of organizational models to nature generally. As interpreted by R-theory, such "modeling relations" describe reality in terms of information relations (encoding and decoding) between measurable existence (expressed as material states and established by efficient behavior) and implicate organization or identity (expressed as formal potential and established by final exemplar), thus capturing all four of Aristotle's causalities within nature (Aristotle defined final cause as immanent from outside of nature). Applied to space-time physics, it claims that space-time is real but established only in relation to existing events, as a formal cause or model for the location of events relative to each other; and in reverse a system of space-time events establishes a template for space-time. R-theory is thus a form of model-dependent realism. It claims to more closely follow the views of Mach, Leibniz, Wheeler and Bohm, suggesting that natural law itself is system-dependent.

Standard Gibbs free energy of formation

The standard Gibbs free energy of formation of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C).

The table below lists the Standard Gibbs function of formation for several elements and chemical compounds and is taken from Lange's Handbook of Chemistry. Note that all values are in kJ/mol. Far more extensive tables can be found in the CRC Handbook of Chemistry and Physics and the NIST JANAF tables. The NIST Chemistry WebBook (see link below) is an online resource that contains standard enthalpy of formation for various compounds along with the standard absolute entropy for these compounds from which the Standard Gibbs Free Energy of Formation can be calculated.

State of matter

In physics, a state of matter is one of the distinct forms in which matter can exist. Four states of matter are observable in everyday life: solid, liquid, gas, and plasma. Many other states are known to exist, such as glass or liquid crystal, and some only exist under extreme conditions, such as Bose–Einstein condensates, neutron-degenerate matter, and quark-gluon plasma, which only occur, respectively, in situations of extreme cold, extreme density, and extremely high-energy. Some other states are believed to be possible but remain theoretical for now. For a complete list of all exotic states of matter, see the list of states of matter.

Historically, the distinction is made based on qualitative differences in properties. Matter in the solid state maintains a fixed volume and shape, with component particles (atoms, molecules or 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, but as well as neutral atoms, it contains a significant number of ions and electrons, both of which can move around freely.

The term phase is sometimes used as a synonym for state of matter, but a system can contain several immiscible phases of the same state of matter.


The T-3000 is a fictional cyborg assassin, serving as the primary antagonist in Terminator Genisys, the fifth installment in the Terminator series, portrayed by Jason Clarke. In the film, the T-3000 is an alternate timeline counterpart of Skynet's (portrayed by Matt Smith) nemesis John Connor (also portrayed by Clarke), created after Skynet infects a variant of Connor with nanotechnology and fractures the timeline. T-3000 also serves as a foil personality to "Guardian" (a reprogrammed T-800 portrayed by Arnold Schwarzenegger), a protagonist who is somewhat similar to T-3000 but also opposite in many ways, of their relationship dynamics with Sarah Connor (portrayed by Emilia Clarke) and Kyle Reese (portrayed by Jai Courtney).

The T-3000's sole mission is to protect and ensure the ultimate survival of Skynet, which seeks to eliminate the human race with its global machine network. The T-3000 describes itself as neither machine nor human; rather, it is a hybrid nanotechnological cyborg. Producer David Ellison explains that the title Terminator Genisys "[is] in reference to genesis, which is in reference to the singularity and the man-machine hybrid that John Connor ends up being."

Terminator Genisys

Terminator Genisys is a 2015 American science-fiction action film directed by Alan Taylor and written by Laeta Kalogridis and Patrick Lussier. The fifth installment in the Terminator franchise, it serves as a soft reboot of the series, using the plot element of time travel to erase the events of the previous films from the series' continuity. It stars Arnold Schwarzenegger, who reprises his role as the Terminator, alongside Jason Clarke, Emilia Clarke, Jai Courtney, J. K. Simmons, Dayo Okeniyi, Matt Smith, Courtney B. Vance, and Lee Byung-hun. It follows soldier Kyle Reese, a soldier in the war against Skynet, who is sent from 2029 to 1984 by John Connor, leader of the Human Resistance, to protect his mother Sarah. When Kyle arrives in the past, he discovers that the timeline has been altered and Sarah has been raised by a reprogrammed Terminator.

Megan Ellison and her production company Annapurna Pictures acquired the franchise rights in May 2011. The following year, production of another installment in the series was set up in collaboration with Skydance Productions, owned by Ellison's brother David. The Ellisons consulted Terminator creator James Cameron in the hope of returning to the spirit of The Terminator (1984) and its sequel Terminator 2: Judgment Day (1991). Principal photography was primarily in New Orleans, with some in the on-screen setting of San Francisco. Six companies handled the film's visual effects, with its prosthetic make-up and animatronics created by Legacy Effects.

The film was released by Paramount Pictures on July 1, 2015, in RealD 3D and IMAX 3D. It was not well-received by critics, who found its story and performances unsatisfactory, although Schwarzenegger's return to the franchise was praised. Terminator Genisys grossed over $440 million worldwide, making it the second-highest-grossing film of the franchise and of Schwarzenegger's career, behind Terminator 2: Judgment Day. Originally planned as the first film of a new trilogy, it was announced in 2017 that the film franchise would be rebooted once again following the return of creative control to Cameron.

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