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Encyclopedia > Gas phase

In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i.e. density, crystal structure, index of refraction, and so forth). The most familiar examples of phases are solids, liquids, and gases. Less familiar phases include: plasmas and quark-gluon plasmas; Bose-Einstein condensates and fermionic condensates; strange matter; liquid crystals; superfluids and supersolids; and the paramagnetic and ferromagnetic phases of magnetic materials. Physical science is an encompassing term for the branches of natural science, and science (generally), that study non-living systems, in contrast to the biological sciences. ... In mathematics, a set can be thought of as any collection of distinct things considered as a whole. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... Rose des Sables (Sand Rose), formed of gypsum crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ... In jewelry, a solid gold piece is the alternative to gold-filled or gold-plated jewelry. ... A liquid will assume the shape of its container. ... A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... A Plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation In physics and chemistry, a plasma is an ionized gas, and is usually considered to be a distinct phase of matter. ... A quark-gluon plasma (QGP) is a phase of quantum chromodynamics (QCD) which exists at extremely high temperature and density. ... A Bose-Einstein condensate is a phase of matter formed by bosons cooled to temperatures very near to absolute zero. ... It has been suggested that this article or section be merged with fermion condensate. ... Strange matter is an ultra-dense phase of matter that is theorized to form inside particularly massive neutron stars. ... Schlieren texture of Liquid Crystal nematic phase Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid, and those of a solid crystal. ... Superfluidity is a phase of matter characterised by the complete absence of viscosity. ... A supersolid is a spatially ordered superfluid. ... Paramagnetism is the tendency of the atomic magnetic dipoles to align with an external magnetic field. ... Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ... Magnetic lines of force of a bar magnet shown by iron filings on paper A magnet is an object that has a magnetic field. ...


Phases are sometimes called states of matter, but this term can lead to confusion with thermodynamic states. For example, two gases maintained at different pressures are in different thermodynamic states, but the same "state of matter". Thermodynamics (from the Greek thermos meaning heat and dynamis meaning power) is a branch of physics that studies the effects of temperature, pressure, and volume changes on physical systems at the macroscopic scale. ...

Contents


Definition

Even though the concept of phases is widely-used in the physical sciences, it is not easy to define precisely. In order to understand the general definition, it is useful to consider two common examples of phase phenomena: firstly, the ordinary solid, liquid, and gas phases of matter; secondly, the paramagnetic and ferromagnetic phases of magnetic materials. In jewelry, a solid gold piece is the alternative to gold-filled or gold-plated jewelry. ... A liquid will assume the shape of its container. ... A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... Paramagnetism is the tendency of the atomic magnetic dipoles to align with an external magnetic field. ... Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ...


Example 1: Solid, liquid, and gas phases

Water (H2O) is composed of water molecules, each of which is an oxygen atom attached to two hydrogen atoms. At room temperature, the molecules are packed closely together, and interact weakly. They do not stick together, and are able to slide past one another like the sand grains in an hourglass. This microscopic behavior of water molecules gives rise to the physical properties of liquid water with which we are all familiar. Because the molecules do not form any rigid structure, water has no fixed shape, and adapts to the shape of any container in which it is placed. Because the molecules are very close to one another, water resists compression; try squeezing a water balloon, and you will find that it is practically impossible to reduce its volume, unlike an ordinary air balloon. Water (from the Old English word wæter; c. ... In general, a molecule is the smallest particle of a pure chemical substance that still retains its composition and chemical properties. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Properties An atom (Greek άτομον from ά: non and τομον: divisible) is a submicroscopic structure found in all ordinary matter. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Room temperature, in laboratory reports, is taken to be roughly 21–23 degrees Celsius (69-73 degrees Fahrenheit), or 294–296 kelvins. ... Hourglass in wooden stand An hourglass, also known as a sandglass or sand timer, is a device for the measurement of time. ... There are several types of compression: physical compression data compression multimedia compression image compression executable compression audio compression video compression bandwidth compression audio level compression compression (functional analysis) See also Arch bridge Compression arch suspended-deck bridge Compressor Compression ratio This is a disambiguation page, a list of pages that... A water bomb, or water balloon, is a simple small latex rubber balloon filled with tap water. ...


If we make slight changes in the physical conditions, such as lowering the temperature, we will observe no abrupt changes in the properties of water. Cold water behaves little differently from lukewarm water. For instance, its compressibility changes slightly with temperature, but remains very low. Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ...


However, if we reduce the temperature below a certain point, an abrupt and dramatic change occurs. At the microscopic level, the molecules suddenly align with one another to form a rigid hexagonal lattice, losing the ability to slide past one another. The system as a whole acquires rigidity, and can hold a definite shape (though it may deform or fracture into pieces if sufficient force is applied.) This is the solid phase of water, commonly known as ice. The transition from a liquid phase to a solid phase is called freezing (or "melting" if we go in the opposite direction), and it is a type of phenomenon known as a phase transition. In crystallography, the hexagonal crystal system is one of the 7 lattice point groups. ... ICE can refer to: InterCity Express, a German high-speed train Internal combustion engine, a fuel engine In-circuit emulator, a computer hardware device In case of emergency, emergency number in mobile phones Institution of Civil Engineers, British civil engineer guild Immigration and Customs Enforcement, U.S. government agency Iron... Physics In physics, melting is the process of heating a solid substance to a point (called melting point) where it turns liquid. ... In physics, a phase transition, (or phase change) is the transformation of a thermodynamic system from one phase to another. ...


Another phase transition, known as boiling, occurs if we raise the temperature of liquid water past a certain point. The water abruptly enters a gaseous phase, where it is called water vapor. In the gaseous phase, the molecules are spread far apart, and interact extremely weakly. Like a liquid, a gas has no fixed shape, but unlike a liquid, it has little resistance to compression because there is enough space for the molecules to move closer to one another. Whereas a liquid placed in a container will form a puddle at the bottom of the container, a gas will expand to fill the container. Boiling is the rapid vaporization of a liquid, which typically occurs when a liquid is heated to a temperature such that its vapor pressure is above that of the surroundings. ... Water vapor or water vapour, also aqueous vapour, is the gas phase of water. ...


We can use other physical parameters, not just temperature, to produce these phase transitions. For example, we can change a liquid into a gas by decreasing the pressure, or, equivalently, increasing the volume. As before, small changes do not have much effect; the phase transition occurs abruptly when the change exceeds a certain amount.


Example 2: Magnetic phases

A second example of phases occurs in magnetic materials. In these materials, each atom possesses a magnetic moment that produces a tiny magnetic field pointing in a certain direction. The atoms are free to rotate, so their magnetic fields can point anywhere, but the magnetic fields of neighboring moments tend to make them line up with one another. At high temperatures, and in the absence of an external magnetic field, individual moments tend to be aligned with only a few neighbors, so the moments tend to point in random directions. There is no net magnetic field, i.e. zero magnetization. This is known as the paramagnetic phase. In physics, the magnetic moment of an object is a vector relating the aligning torque in a magnetic field experienced by the object to the field vector itself. ... This article needs to be cleaned up to conform to a higher standard of quality. ...


If we lower the temperature below a certain point, called the Curie point, the moments abruptly line up over large regions (usually many thousands of atoms). Within these regions, called "magnetic domains", almost all the moments are pointing in the same direction. This is known as spontaneous magnetization. The appearance of magnetic domains is a phase transition, and the new phase is known as a ferromagnet. In physics, the Curie point, or Curie temperature, is the temperature above which a ferromagnet loses its ferromagnetic ability to possess a net (spontaneous) magnetization in the absence of an external magnetic field. ... A ferromagnet is a piece of ferromagnetic material, in which the microscopic magnetized regions, called domains, have been aligned by an external magnetic field (e. ...


General definition of phases

In general, we say that two different states of a system are in different phases if there is an abrupt change in their physical properties while transforming from one state to the other. Conversely, two states are in the same phase if they can be transformed into one another without any abrupt changes.


An important point is that different types of phases are associated with different physical quantities. When discussing the solid, liquid, and gaseous phases, we talked about rigidity and compressibility, and the effects of varying the pressure and volume, because those are the relevant properties that distinguish a solid, a liquid, and a gas. On the other hand, when discussing paramagnetism and ferromagnetism, we looked at the magnetization, because that is what distinguishes the ferromagnetic phase from the paramagnetic phase. Several more examples of phases will be given in the following section. Paramagnetism is the tendency of the atomic magnetic dipoles to align with an external magnetic field. ... Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ...


Not all physical quantities are relevant when we are looking at a certain system. For example, it is generally not useful for us to compare the magnetization of liquid water to the magnetization of ice. In this sense, what constitutes a "phase" depends on what parameters you are looking at, and vice versa. It is this idea that allows us to generalize the concept of phases to encompass a wide variety of phenomena.


In more technical language, a phase is a region in the parameter space of thermodynamic variables in which the free energy is analytic. As long as the free energy is analytic, all thermodynamic properties (such as entropy, heat capacity, magnetization, and compressibility) will be well-behaved, because they can be expressed in terms of the free energy and its derivatives. For example, the entropy is the first derivative of the free energy with temperature. In statistics one can study the distribution of a random variable. ... Thermodynamics (from the Greek thermos meaning heat and dynamis meaning power) is a branch of physics that studies the effects of temperature, pressure, and volume changes on physical systems at the macroscopic scale. ... The free energy is a measure of the amount of mechanical (or other) work that can be extracted from a system, and is helpful in engineering applications. ... In mathematics, an analytic function is a function that is locally given by a convergent power series. ... The thermodynamic entropy S, often simply called the entropy in the context of thermodynamics, is a measure of the amount of energy in a physical system that cannot be used to do work. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Fluid Dynamics Compressibility (physics) is a measure of the relative volume change of fluid or solid as a response to a pressure (or mean stress) change: . For a gas the magnitude of the compressibility depends strongly on whether the process is adiabatic or isothermal, while this difference is small in... Mathematicians (and those in related sciences) very frequently speak of whether a mathematical object -- a number, a function, a set, a space of one sort or another -- is well-behaved or not. ... In mathematics, the derivative is one of the two central concepts of calculus. ... The thermodynamic entropy S, often simply called the entropy in the context of thermodynamics, is a measure of the amount of energy in a physical system that cannot be used to do work. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ...


When a system goes from one phase to another, there will generally be a stage where the free energy is non-analytic. This is a phase transition. Due to this non-analyticity, the free energies on either side of the transition are two different functions, so one or more thermodynamic properties will behave very differently after the transition. The property most commonly examined in this context is the heat capacity. During a transition, the heat capacity may become infinite, jump abruptly to a different value, or exhibit a "kink" or discontinuity in its derivative. See also differential scanning calorimetry. In physics, a phase transition, (or phase change) is the transformation of a thermodynamic system from one phase to another. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In mathematics, the derivative is one of the two central concepts of calculus. ... Differential scanning calorimetry (DSC) is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference are measured as a function of temperature. ...

Image:Heat-capacity-transition.png
Possible graphs of heat capacity (C) against temperature (T) at a phase transition.

Diagram of heat capacity behavior in phase transitions File links The following pages link to this file: Phase (matter) Categories: Images with unknown source ...

Other examples of phases

Main article: List of phases of matter This is a list of the different phases of matter including the more exotic ones. ...


In this section, we will present several systems that exhibit phase phenomena.


We have discussed the solid, liquid, and gaseous phases of ordinary matter. It turns out that other configurations of molecules are possible, corresponding to novel phases. Amorphous solids, or glasses, are a phase intermediate between solids and liquids. The atoms in an amorphous solid are aligned in a rigid disorderly structure, instead of a regular lattice like an ordinary ("crystalline") solid. Liquid crystals are another phase intermediate between solids and liquids; the atoms are held in place, but are free to rotate. An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. ... This article refers to the material. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... Schlieren texture of Liquid Crystal nematic phase Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid, and those of a solid crystal. ...


In many materials, there are actually a variety of solid phases, each corresponding to a unique crystal structure. These varying crystal phases of the same substance are called "allotropes" if intramolecular bonding changes or "polymorphs" if only intermolecular bonding changes. For instance, there are at least nine different polymorphs of ice that manifest under different temperature and pressure conditions. To take another example, diamond and graphite are allotropes of carbon. Graphite is composed of layers of hexagonally arranged carbon atoms, in which each carbon atom is strongly bound to three neighboring atoms in the same layer and is weakly bound to atoms in the neighboring layers. By contrast, in diamond each carbon atom is strongly bound to four neighboring carbon atoms in a cubic array. The unique crystal structures of graphite and diamond are responsible for the vastly different properties of these two materials. Rose des Sables (Sand Rose), formed of gypsum crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... This article is in need of attention from an expert on the subject. ... ICE can refer to: InterCity Express, a German high-speed train Internal combustion engine, a fuel engine In-circuit emulator, a computer hardware device In case of emergency, emergency number in mobile phones Institution of Civil Engineers, British civil engineer guild Immigration and Customs Enforcement, U.S. government agency Iron... For other uses, see Diamond (disambiguation). ... Graphite (named by Abraham Gottlob Werner in 1789, from the Greek γραφειν: to draw/write, for its use in pencils) is one of the allotropes of carbon. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ...


In an ordinary gas phase, the electrons are tightly bound to the atomic nuclei. In contrast, in the plasma phase the atoms are dissociated, i.e. the electrons are separated from the atomic nuclei. This dissociation, or ionization, occurs abruptly upon raising the temperature and lowering the pressure, and thus displays the hallmarks of a phase transition. (It is commonly stated that plasmas are the "fourth state of matter", but the above discussion shows that this statement is false. There are a huge variety of phases, or "states of matter", depending on what physical properties you are looking at.) Properties The electron is a fundamental subatomic particle that carries a negative electric charge. ... A stylized representation of a lithium atom. ... A Plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation In physics and chemistry, a plasma is an ionized gas, and is usually considered to be a distinct phase of matter. ... // An ion is an atom or group of atoms with a net electric charge. ...


Superfluids, supersolids, and Bose-Einstein condensates are phases of matter that occur at extremely low temperatures, near absolute zero. These temperatures are too low to occur anywhere on Earth except in laboratory experiments. The very slow motion of molecules at these temperatures allow some of the more bizarre aspects of quantum mechanics to manifest themselves in the form of novel macroscopic properties. Superfluidity is a phase of matter characterised by the complete absence of viscosity. ... A supersolid is a spatially ordered superfluid. ... A Bose-Einstein condensate is a phase of matter formed by bosons cooled to temperatures very near to absolute zero. ... Absolute zero is a fundamental lower bound on the temperature of any macroscopic system. ...


Under extremely high pressure, ordinary matter undergoes a transition to a series of exotic phases collectively known as degenerate matter. These phases are of great interest to astrophysics, because these high-pressure conditions are believed to take place inside stars that have used up their nuclear fusion "fuel", such as white dwarfs and neutron stars. Degenerate matter is matter which has sufficiently high density that the dominant contribution to its pressure arises from the Pauli exclusion principle. ... Spiral Galaxy ESO 269-57 Astrophysics is the tree of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, temperature and chemical composition) of astronomical objects such as stars, galaxies, and the interstellar medium, as well as their interactions. ... The Pleiades star cluster A star is a massive body of plasma in outer space that is currently producing or has produced energy through nuclear fusion. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... White dwarf Sirius-B in x-rays A white dwarf is an astronomical object which is produced when a low or medium mass star dies. ... Neutron stars are one of the few possible endpoints of stellar evolution. ...


Phase transitions also play an extremely important role in cosmology. It is believed that the universe as a whole underwent a series of important phase transitions during its early history, shortly after the Big Bang. A major branch of theoretical cosmology, inflation theory, seeks to explain various aspects of the modern universe, such as why the universe is so flat, as the effect of one or more of these transitions. These transitions are of great interest to particle physics as well, as it has been hypothesized that the quantum field that fills spacetime (a particle physics concept that incorporates "material" particles like electrons as well as "field-like" particles such as photons and gluons) underwent a series of transitions from a highly "symmetric" phase in which all fundamental forces were unified into a single entity, into the "broken symmetry" phase that we observe today, in which there are four fundamental forces with very different strengths. Cosmology, from the Greek: κοσμολογία (cosmologia, κόσμος (cosmos) world + λογια (logia) discourse) is the study of the universe in its totality and by extension mans place in it. ... According to the Big Bang theory, the Universe originated in an extremely dense and hot state (bottom). ... Inflation is the idea—first proposed by Alan Guth (1981)—that the nascent universe passed through a phase of exponential expansion (the inflationary epoch) that was driven by a negative pressure vacuum energy density. ... The flatness problem is a cosmological problem with the Big Bang theory, which is solved by hypothesising an inflationary universe. ... Particles erupt from the collision point of two relativistic (100GeV) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... Quantum field theory (QFT) is the application of quantum mechanics to fields. ... World line of the orbit of the Earth depicted in two spatial dimensions X and Y (the plane of the Earth orbit) and a time dimension, usually put as the vertical axis. ... In physics, the photon (from Greek φως, phōs, meaning light) is the quantum of the electromagnetic field, for instance light. ... In particle physics, gluons are vector gauge bosons that mediate strong color charge interactions of quarks in quantum chromodynamics (QCD). ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... Spontaneous symmetry breaking in physics takes place when a system that is symmetric with respect to some symmetry group goes into a vacuum state that is not symmetric. ...


Phase diagrams

Main article: Phase diagram In physical chemistry and materials science, a phase diagram is a type of graph used to show the equilibrium conditions between the thermodynamically-distinct phases. ...


The different phases of a system may be represented using a phase diagram. The axes of the diagrams are the relevant thermodynamic variables. For simple mechanical systems, we generally use the pressure and temperature. The following figure shows a phase diagram for a typical material exhibiting solid, liquid and gaseous phases. Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ...

A typical phase diagram
A typical phase diagram.

The markings on the phase diagram show the points where the free energy is non-analytic. The open spaces, where the free energy is analytic, correspond to the phases. The phases are separated by lines of non-analyticity, where phase transitions occur, which are called phase boundaries. Image:Phase-diag. ...


In the above diagram, the phase boundary between liquid and gas does not continue indefinitely. Instead, it terminates at a point on the phase diagram called the critical point. At temperatures and pressure above the critical point, the physical property differences that differentiate the liquid phase from the gas phase become less defined. This reflects the fact that, at extremely high temperatures and pressures, the liquid and gaseous phases become indistinguishable. In water, the critical point occurs at around 647 K (374 °C or 705 °F) and 22.064 MPa. In chemistry and condensed matter physics, a critical point specifies the conditions (temperature, pressure) at which the liquid state of the matter ceases to exist. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... The pascal (symbol Pa) is the SI unit of pressure. ...


The existence of the liquid-gas critical point reveals a slight ambiguity in our above definitions. When going from the liquid to the gaseous phase, one usually crosses the phase boundary, but it is possible to choose a path that never crosses the boundary by going to the right of the critical point. Thus, phases can sometimes blend continuously into each other. This new phase which has some properties that are similar to a liquid and some properties that are similar to a gas is call a supercritical fluid. We should note, however, that this does not always happen. For example, it is impossible for the solid-liquid phase boundary to end in a critical point in the same way as the liquid-gas boundary, because the solid and liquid phases have different symmetry. Square with symmetry group D4 Symmetry is a characteristic of geometrical shapes, equations, and other objects; we say that such an object is symmetric with respect to a given operation if this operation, when applied to the object, does not appear to change it. ...


An interesting thing to note is that the solid-liquid phase boundary in the phase diagram of most substances, such as the one shown above, has a positive slope. This is due to the solid phase having a higher density than the liquid, so that increasing the pressure increases the melting temperature. However, in the phase diagram for water the solid-liquid phase boundary has a negative slope. This reflects the fact that ice has a lower density than water, which is an unusual property for a material. Water (from the Old English word wæter; c. ...


Metastable phases

Sometimes a substance or mixture can be heated, compressed, etc., beyond the point at which it would normally exhibit a phase change, but without actually triggering the change. Examples include supercooling, superheating, and supersaturation. Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid. ... In physics, superheating (sometimes referred to as boiling retardation, boiling delay, or defervescence) is the phenomenon in which a liquid is heated to a temperature higher than its standard boiling point, without actually boiling. ... HI JAMIE!!!!! In chemistry, the term supersaturation or oversaturation refers to a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances. ...


Such metastable states may sometimes be considered as phases, although strictly speaking they are not because they are unstable. For example, each polymorph of a given substance is usually only stable over a specific range of conditions. For example, diamond is only stable at extremely high pressures. Graphite is the stable form of carbon at normal atmospheric pressures. Although diamond is not stable at atmospheric pressures and should transform to graphite, we know that diamonds exist at these pressures. This is because at normal temperatures the transformation from diamond to graphite is extremely slow. If we were to heat the diamond, the rate of transformation would increase and the diamond would become graphite. However, at normal temperatures the diamond can persist for a very long time. Metastability is the ability of a non-equilibrium state to persist for a long period of time. ...


Another important example of metastable polymorphs occurs in the processing of steel. Steels are often subjected to a variety of thermal treatments designed to produce various combinations of stable and metastable iron phases. In this way the steel properties, such as hardness and strength can be adjusted by controlling the relative amounts and crystal sizes of the various phases that form. The old steel cable of a colliery winding tower Steel is a metal alloy whose major component is iron, with carbon being the primary alloying material. ...


Phase equilibrium

The distribution of kinetic energy among molecules is not uniform, and it changes randomly. This means that at, say, the surface of a liquid, there may be an individual molecule with enough kinetic energy to jump into the gas phase. Likewise, individual gas molecules may have low enough kinetic energy to join other molecules in the liquid phase. This phenomena means that at any given temperature and pressure, multiple phases may co-exist.


For example, under standard conditions for temperature and pressure, a bowl of liquid water in dry air will evaporate until the partial pressure of gaseous water equals the vapor pressure of water. At this point, the rate of molecules leaving and entering the liquid phase becomes the same (due to the increased number of gaseous water molecules available to re-condense). The fact that liquid molecules with above-average kinetic energy have been removed from the bowl results in evaporative cooling. Similar processes may occur on other types of phase boundaries. // Standard Reference Conditions For Expressing Gas Volumes It is absolutely necessary to define the standard reference conditions of temperature and pressure when expressing a gas volume or a volumetric flow rate because the volume of a gas varies with the temperature and pressure of the gas. ... The partial pressure of a gas in a mixture or solution is what the pressure of that gas would be if all other components of the mixture or solution suddenly vanished without its temperature changing. ... The vapor pressure is the pressure (if the vapor is mixed with other gases, the partial pressure) of a vapor (this vapour being formed from molecules/atoms escaping from a liquid/solid). ... Evaporative cooling is a system in which latent heat of evaporation is used to carry heat away from an object to cool it. ...


Gibbs' phase rule relates the number of possible phases, variables such as temperature and pressure, and whether or not an equilibrium will be reached. Josiah Willard Gibbs (February 11, 1839 – April 28, 1903) was an American mathematical physicist who contributed much of the theoretical foundation that led to the development of chemical thermodynamics and was one of the founders of vector analysis. ... It has been suggested that this article or section be merged with Gibbs phase rule. ...


Emergence and universality

Phases are emergent phenomena produced by the self-organization of a macroscopic number of particles. Typical samples of matter, for example, contain around 1023 particles (of the order of Avogadro's number). In systems that are too small -- even, say, a thousand atoms -- the distinction between phases disappears, since the appearance of non-analyticity in the free energy requires a huge, formally infinite, number of particles to be present. A termite cathedral mound produced by a termite colony: a classic example of emergence. ... Avogadros number, also called Avogadros Constant (NA) is a large constant used in chemistry and physics. ...


One might ask why real systems exhibit phases, since they are not actually infinite. The reason is that real systems contain thermodynamic fluctuations. When a system is far from a phase transition, these fluctuations are unimportant, but as it approaches a phase transition, the fluctuations begin to grow in size (i.e. spatial extent). At the ideal transition point, their size would be infinite, but before that can happen the fluctuations will have become as large as the system itself. In this regime, "finite-size" effects come into play, and we are unable to accurately predict the behavior of the system. Thus, phases in a real system are only well-defined away from phase transitions, and how far away it needs to be is dependent on the size of the system.


There is a corollary to the emergent nature of phase phenomena, known as the principle of universality. The properties of phases are largely independent of the underlying microscopic physics, so that the same types of phases arise in a wide variety of systems. This is a familiar fact of life. We know, for example, that the property that defines a solid -- resistance to deformation -- is exhibited by materials as diverse as iron, ice, and Silly Putty. The only differences are matters of scale. Iron may resist deformation more strongly than Silly Putty, but both maintain their shape if the applied forces are not too strong. General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... ICE can refer to: InterCity Express, a German high-speed train Internal combustion engine, a fuel engine In-circuit emulator, a computer hardware device In case of emergency, emergency number in mobile phones Institution of Civil Engineers, British civil engineer guild Immigration and Customs Enforcement, U.S. government agency Iron... It has been suggested that Thinking Putty be merged into this article or section. ...


External links

Chemical structure of the three main types of cyclodextrins. ... Water (from the Old English word wæter; c. ...

See also


Condensed matter physics is the field of physics that deals with the macroscopic physical properties of matter. ... A cooling curve of naphthalene from liquid to solid. ... Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid. ... In physics, superheating (sometimes referred to as boiling retardation, boiling delay, or defervescence) is the phenomenon in which a liquid is heated to a temperature higher than its standard boiling point, without actually boiling. ... A multiphasic liquid, also known as a multiphasic liquid-liquid-liquid system, is a mixture consisting of more than two immiscible liquid phases. ...

Phases of matter
Solid | Amorphous solid | Liquid | Gas | Plasma | Superfluid | Supersolid | Degenerate matter | Quark-gluon plasma | Fermionic condensate | Bose-Einstein condensate | Strange matter

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