WordNet

arrange in phases or stages; "phase a withdrawal"
(physical chemistry) a distinct state of matter in a system; matter that is identical in chemical composition and physical state and separated from other material by the phase boundary; "the reaction occurs in the liquid phase of the system" (同)form
a particular point in the time of a cycle; measured from some arbitrary zero and expressed as an angle (同)phase_angle
any distinct time period in a sequence of events; "we are in a transitional stage in which many former ideas must be revised or rejected" (同)stage
adjust so as to be in a synchronized condition; "he phased the intake with the output of the machine"
(astronomy) the particular appearance of a bodys state of illumination (especially one of the recurring shapes of the part of Earths moon that is illuminated by the sun); "the full phase of the moon"
attack with gas; subject to gas fumes; "The despot gassed the rebellious tribes"
the state of matter distinguished from the solid and liquid states by: relatively low density and viscosity; relatively great expansion and contraction with changes in pressure and temperature; the ability to diffuse readily; and the spontaneous tendency to become distributed uniformly throughout any container (同)gaseous state
a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely
a unit of force equal to the force exerted by gravity; used to indicate the force to which a body is subjected when it is accelerated (同)gee, g-force

PrepTutorEJDIC

(変化・発達の)『段階』,『局面』 / (物事の)『面』,様相《+『of』+『名』》 / (月・惑星などの)相 / …‘を'段階的に調整(整理)する
〈U〉〈C〉『気体』,『ガス』 / 〈U〉(灯用・燃料用)ガス / 〈U〉《米話》=gasoline / 〈U〉(麻酔用の)亜酸化窒素,笑気(laughing gas);毒ガス(mustard gas, tear gasなど) / 〈U〉《話》むだ話,ばか話 / 〈C〉《単数形で》とても楽しいこと / 〈敵など〉‘を'毒ガスで攻撃する / 《米話》〈車〉‘に'ガソリンを入れる《+『up』+『名,』+『名』+『up』》 / 長々とむだ話をする

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/06/06 23:19:37」(JST)

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Not to be confused with State of 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] 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 over the water is a third phase. 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.

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

Types of phases

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. ^[2] 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.^[3]

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 liquid begins to condense, 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 kinetic energy expended as the evaporating molecules escape the attractive forces of the liquid is reflected in a decrease in temperature. The amount of energy required to induce the transition is more than the amount required to heat the water from room temperature to just short of boiling temperature, which is why 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.

Notes and references

^ Modell, Michael; Robert C. Reid (1974). Thermodynamics and Its Applications. Englewood Cliffs, NJ: Prentice-Hall. ISBN 0-13-914861-2. Cite uses deprecated parameters (help)
^ 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 3-527-60567-3.
^ 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.

External links

Wikimedia Commons has media related to State of aggregation.

French physicists find a solution that reversibly solidifies with a rise in temperature – α-cyclodextrin, water, and 4-methylpyridine

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English Journal

Optimization of matrix solid-phase dispersion for the rapid determination of salicylate and benzophenone-type UV absorbing substances in marketed fish.

Tsai DY1, Chen CL1, Ding WH2.Author information 1Department of Chemistry, National Central University, Chung-Li 320, Taiwan.2Department of Chemistry, National Central University, Chung-Li 320, Taiwan. Electronic address: wanghsiending@gmail.com.AbstractA simple and effective method for the rapid determination of five salicylate and benzophenone-type UV absorbing substances in marketed fish is described. The method involves the use of matrix solid-phase dispersion (MSPD) prior to their determination by on-line silylation gas chromatography tandem mass spectrometry (GC-MS/MS). The parameters that affect the extraction efficiency were optimized using a Box-Behnken design method. The optimal extraction conditions involved dispersing 0.5g of freeze-dried powdered fish with 1.0g of Florisil using a mortar and pestle. This blend was then transferred to a solid-phase extraction (SPE) cartridge containing 1.0g of octadecyl bonded silica (C18), as the clean-up co-sorbent. The target analytes were then eluted with 7mL of acetonitrile. The extract was derivatized on-line in the GC injection-port by reaction with a trimethylsilylating (TMS) reagent. The TMS-derivatives were then identified and quantitated by GC-MS/MS. The limits of quantitation (LOQs) were less than 0.1ng/g.
Food chemistry.Food Chem.2014 Jul 1;154:211-6. doi: 10.1016/j.foodchem.2014.01.013. Epub 2014 Jan 10.
A simple and effective method for the rapid determination of five salicylate and benzophenone-type UV absorbing substances in marketed fish is described. The method involves the use of matrix solid-phase dispersion (MSPD) prior to their determination by on-line silylation gas chromatography tandem m
PMID 24518335

Risk assessment for the Italian population of acetaldehyde in alcoholic and non-alcoholic beverages.

Paiano V1, Bianchi G2, Davoli E2, Negri E3, Fanelli R2, Fattore E2.Author information 1Department of Environmental Health Sciences, IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, via Giuseppe La Masa 19, 20156 Milan, Italy. Electronic address: viviana.paiano@marionegri.it.2Department of Environmental Health Sciences, IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, via Giuseppe La Masa 19, 20156 Milan, Italy.3Department of Epidemiology, IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, via Giuseppe La Masa 19, 20156 Milan, Italy.AbstractAcetaldehyde is a naturally-occurring carcinogenic compound, present in different food items, especially in alcoholic beverages. The aims of this study were to measure acetaldehyde concentration in different beverages consumed in Italy and to estimate the potential cancer risk. The analytical procedure was based on headspace solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS), using the isotopic dilution method. The margin of exposure (MOE) approach of the European Food Safety Authority (EFSA) was used for risk characterisation. The highest concentrations (median, min-max) were detected in grappa samples (499, 23.4-1850mg/l), followed by fruit-based liqueurs and spirits (62.0, 5.23-483mg/l) and wine (68.0, 18.1-477mg/l); the lowest were detected in gin (0.91, 0.78-1.90mg/l). The lowest MOE was estimated for high wine consumers (69). These results suggest that regulatory measures and consumer guidance may be necessary for acetaldehyde in beverages.
Food chemistry.Food Chem.2014 Jul 1;154:26-31. doi: 10.1016/j.foodchem.2013.12.098. Epub 2014 Jan 8.
Acetaldehyde is a naturally-occurring carcinogenic compound, present in different food items, especially in alcoholic beverages. The aims of this study were to measure acetaldehyde concentration in different beverages consumed in Italy and to estimate the potential cancer risk. The analytical proced
PMID 24518311

A multi-residue method for the determination of pesticides in tea using multi-walled carbon nanotubes as a dispersive solid phase extraction absorbent.

Hou X1, Lei S2, Qiu S2, Guo L2, Yi S2, Liu W2.Author information 1Center of Analysis and Testing, Sichuan Academy of Agricultural Sciences, Chengdu 610066, PR China; Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, PR China; University of Chinese Academy of Sciences, Beijing 100039, PR China. Electronic address: houxue127@163.com.2Center of Analysis and Testing, Sichuan Academy of Agricultural Sciences, Chengdu 610066, PR China.AbstractA modified QuEChERS (quick, easy, cheap, effective, rugged and safe) method using multi-walled carbon nanotubes (MWCNTs) as a dispersive solid phase extraction (d-SPE) absorbent was established for analysis of 78 pesticide residues in tea. A 6mg MWCNT sample was selected as the optimised amount based on the distribution of pesticide recoveries and clean-up efficiency from 6mL acetonitrile extracts. The matrix effects of the method were evaluated and matrix-matched calibration was recommended. The method was validated employing gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) at the spiked concentration levels of 0.05, 0.1 and 0.15mgkg(-1). For most of the targeted pesticides, the percent recoveries range from 70% to 120%, with relative standard deviations (RSDs) <20%. The linear correlation coefficients (r(2)) were higher than 0.99 at concentration levels of 0.025-0.500mgkg(-1). In this study, MWCNTs were proved to be a promising d-SPE absorbent with excellent cleanup efficiency, which could be widely applied for the analysis of pesticide residues.
Food chemistry.Food Chem.2014 Jun 15;153:121-9. doi: 10.1016/j.foodchem.2013.12.031. Epub 2013 Dec 15.
A modified QuEChERS (quick, easy, cheap, effective, rugged and safe) method using multi-walled carbon nanotubes (MWCNTs) as a dispersive solid phase extraction (d-SPE) absorbent was established for analysis of 78 pesticide residues in tea. A 6mg MWCNT sample was selected as the optimised amount base
PMID 24491709