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Encyclopedia > Critical temperature

It has been suggested that this article or section be merged with :Critical point (thermodynamics). (Discuss)

A typical phase diagram. The dotted green line gives the anomalous behaviour of water

The critical temperature, T_c, of a material is the temperature above which distinct liquid and gas phases do not exist. As the critical temperature is approached, the properties of the gas and liquid phases become the same resulting in only one phase: the supercritical fluid. Above the critical temperature a liquid cannot be formed by an increase in pressure, but with enough pressure a solid may be formed. The critical pressure is the vapor pressure at the critical temperature. On the diagram showing the thermodynamic properties for a given substance, the point at critical temperature and critical pressure is called the critical point of the substance. The critical molar volume is the volume of one mole of material at the critical temperature and pressure. Image File history File links Merge-arrows. ... In physical chemistry, thermodynamics, chemistry and condensed matter physics, a critical point, also called a critical state, specifies the conditions (temperature, pressure) at which the liquid state of the matter ceases to exist. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... For other uses, see Temperature (disambiguation). ... For other uses, see Liquid (disambiguation). ... For other uses, see Gas (disambiguation). ... 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. ... A supercritical fluid is any substance at a temperature and pressure above its thermodynamic critical point. ... This article is about pressure in the physical sciences. ... Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ... In physical chemistry, thermodynamics, chemistry and condensed matter physics, a critical point, also called a critical state, specifies the conditions (temperature, pressure) at which the liquid state of the matter ceases to exist. ... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ... For other uses, see Volume (disambiguation). ...

Critical properties vary from material to material, just as is the case for the melting point and boiling point. Critical properties for many pure substances are readily available in the literature. Obtaining critical properties for mixtures is somewhat more problematic. The melting point of a solid is the temperature range at which it changes state from solid to liquid. ... Italic text This article is about the boiling point of liquids. ...

Two immiscible liquids, such as oil and water, will also have a critical temperature and pressure at which the two phases will become consolute. Miscibility is the ability of two or more substances to mix, and form a single homogeneous phase. ...

1 Table of critical temperature and pressure for selected substances
2 Other uses
- 2.1 Superconductivity
- 2.2 Construction
3 Mathematical definition
4 See also
5 References
6 Further reading

Table of critical temperature and pressure for selected substances

Substance^[1]^[2]	Critical temperature (°C)	Critical temperature (K)	Critical pressure (atm)	Critical pressure (MPa)
Argon	−122.4	150.8	48.1	4.870
Bromine	310.8	584	102	10.340
Chlorine	143.8	417	76.0	7.700
Fluorine	−128.85	144.3	51.5	5.220
Helium	−267.96	5.19	2.24	0.227
Hydrogen	−239.95	33.2	12.8	1.297
Krypton	−63.8	209.4	54.3	5.500
Neon	−228.75	44.4	27.2	2.760
Nitrogen	−146.9	126.2	33.5	3.390
Oxygen	−118.6	154.6	49.8	5.050
CO2	31.04	304.1	72.8	7.377
Xenon	16.6	289.7	57.6	5.840
Lithium	2,950	3,223	65.2	6.700
Mercury	1,476.9	1,750	1,587	160.008
Iron	8,227	8,500
Gold	6,977	7,250	5000	5.300
Aluminium	7,577	7,850
Tungsten	15,227	15,500
Water^[3] ^[4]	373.936	647.096	217.7	22.059

For other uses, see Celsius (disambiguation). ... For other uses, see Kelvin (disambiguation). ... Standard atmosphere (symbol: atm) is a unit of pressure. ... For other uses, see Pascal. ... General Name, symbol, number argon, Ar, 18 Chemical series noble gases Group, period, block 18, 3, p Appearance colorless Standard atomic weight 39. ... Bromo redirects here. ... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Distinguished from fluorene and fluorone. ... General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ... This article is about the chemistry of hydrogen. ... For other uses, see Krypton (disambiguation). ... For other uses, see Neon (disambiguation). ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... This article is about the chemical element and its most stable form, or dioxygen. ... Carbon dioxide is an atmospheric gas composed of one carbon and two oxygen atoms. ... General Name, Symbol, Number xenon, Xe, 54 Chemical series noble gases Group, Period, Block 18, 5, p Appearance colorless Standard atomic weight 131. ... This article is about the chemical element. ... This article is about the element. ... Fe redirects here. ... GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ... Aluminum redirects here. ... For other uses, see Tungsten (disambiguation). ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

Other uses

Superconductivity

In superconductivity applications, critical temperature refers to the temperature below which a given material becomes superconductive. A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. ...

Construction

In construction, critical temperature refers to the temperature above which structural steel loses its strength and is no longer fully capable of loadbearing support. Maintaining structural and important process steel building components below this critical temperature, which varies from country to country but is generally between 500 and 560°C, is an important function of passive fire protection. For other uses, see Construction (disambiguation). ... For other uses, see Steel (disambiguation). ... Fire-resistance rated wall assembly with fire door, cable tray penetration and intumescent [1] cable coating. ...

Mathematical definition

For pure substances, there is an inflection point in the critical isotherm on a pV diagram. This means that at the critical point: Plot of y = x3 with inflection point of (0,0). ... An isotherm is a line of equal or constant temperature on a graph, plot, or map; an isopleth of temperature. ...

$left(frac{partial p}{partial V}right)_T = left(frac{partial^2p}{partial V^2}right)_T = 0.$

This relation can be used to evaluate two parameters for an equation of state in terms of the critical properties.

Sometimes a set of reduced properties are defined in terms of the critical properties, ie.:

T r = T / T c

p r = p / p c

V r = V / V c

The principle of corresponding states indicates that substances at equal reduced pressures and temperatures have equal reduced volumes. This relationship is approximately true for many substances, but becomes increasingly inaccurate for large values of p_r

References

^ Emsley, John (1991). The Elements, (Second Edition), Oxford University Press. ISBN 0-19-855818-X.
^ (2002) Thermodynamics: An Engineering Approach, (Fourth Edition), McGraw-Hill, page 824. ISBN 0-07-238332-1.
^ Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (PDF). Erlangen, Germany. International Association for the Properties of Water and Steam (September 1997). Retrieved on 2006-12-03.
^ Critical Temperature and Pressure. Purdue University. Retrieved on 2006-12-19.

Oxford University Press (OUP) is a highly-respected publishing house and a department of the University of Oxford in England. ... The McGraw-Hill Companies, Inc. ... PDF is an abbreviation with several meanings: Portable Document Format Post-doctoral fellowship Probability density function There also is an electronic design automation company named PDF Solutions. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 337th day of the year (338th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 353rd day of the year (354th in leap years) in the Gregorian calendar. ...

Contents

Table of critical temperature and pressure for selected substances GA_googleFillSlot("encyclopedia_square");