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etween gas and the critical point.|The vapour-liquid critical point in a pressure-temperature phase diagram is at the high-temperature extreme of the liquid-gas phase boundary. (The dotted green line gives the anomalous behaviour of water.)]]--86.96.226.18 (talk) 16:54, 20 February 2013 (UTC)

The vapour pressure is the equilibrium pressure from a liquid or a solid at a specific temperature. The equilibrium vapour pressure of a liquid or solid is not affected by the amount of contact with the liquid or solid interface.

The normal boiling point of a liquid is the temperature at which the vapour pressure is equal to one atmosphere (unit).^[1]

For two-phase systems (e.g., two liquid phases), the vapour pressure of the system is the sum of the vapour pressures of the two liquids. In the absence of stronger inter-species attractions between like-like or like-unlike molecules, the vapour pressure follows Raoult's Law, which states that the partial pressure of each component is the product of the vapour pressure of the pure component and its mole fraction in the mixture. The total vapour pressure is the sum of the component partial pressures.^[2]

Examples

Perfumes contain chemicals that vapourise at different temperatures and at different rate in scent accords known as notes.
Atmospheric water vapour is found near the earth's surface, and may condense into small liquid droplets and form meteorological phenomena such as fog, mist and haar.
Mercury-vapour lamps and sodium vapour lamps produce light from atoms in excited states.

--86.96.226.18 (talk) 16:54, 20 February 2013 (UTC)

Measuring vapour

Since it is in the g--86.96.226.18 (talk) 16:54, 20 February 2013 (UTC)--86.96.226.18 (talk) 16:54, 20 February 2013 (UTC)--86.96.226.18 (talk) 16:54, 20 February 2013 (UTC)as phase, the amount of vapour present is quantified by the partial pressure of the gas. Also, vapours obey the barometric formula in a gravitational field just as conventional atmospheric gases do.

Vapours of flammable liquids

Flammable liquids do not burn when ignited. It is the vapour cloud above the liquid that will burn if the vapour's concentration is between the Lower Flammable Limit (LFL) and Upper Flammable Limit (UFL) of the flammable liquid.

References

^ Petrucci et al. p.484
^ Thomas Engel and Philip Reid, "Physical Chemistry" (Pearson Benjamin-Cummings 2006) p.194

סباص

[1] Petrucci et al. p.484

[2] Thomas Engel and Philip Reid, "Physical Chemistry" (Pearson Benjamin-Cummings 2006) p.194

[1]

[2]

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+etween gas and the critical point.|The vapour-liquid critical point in a pressure-temperature [[phase diagram]] is at the high-temperature extreme of the liquid-gas phase boundary. <small>(The dotted green line gives the anomalous behaviour of water.)</small>]]--[[Special:Contributions/86.96.226.18|86.96.226.18]] ([[User talk:86.96.226.18|talk]]) 16:54, 20 February 2013 (UTC)
-[[File:watervapor cup.jpg|thumb|right|Water condenses into visible droplets after evaporating from a cup of hot tea]]
-A '''vapour'''  (British spelling) or '''vapor''' (see [[spelling differences]]) is a substance in the [[gas]] phase at a [[temperature]] lower than its [[critical temperature|critical point]].<ref>R. H. Petrucci, W. S. Harwood, and F. G. Herring, "General Chemistry", 8th edition (Prentice-Hall 2002), p.486.</ref>
-This means that the vapour can be [[condensation|condensed]] to a [[liquid]] or to a [[solid]] by increasing its [[pressure]] without reducing the temperature.
-For example, water has a critical temperature of 374 °C (647 K), which is the highest temperature at which liquid water can exist. In the [[Earth's atmosphere|atmosphere]] at ordinary temperatures, therefore, gaseous water (known as [[water vapor]]) will condense to liquid if its [[partial pressure]] is increased sufficiently.
-A vapour may co-exist with a liquid (or solid). When this is true, the two phases will be in equilibrium, and the gas pressure will equal the equilibrium [[vapour pressure]] of the liquid (or solid).<ref>Petrucci et al. p.483</ref>
-== Properties ==
-[[Image:phase-diag2.svg|thumb|300px|right|In a typical phase diagram, the boundary between gas and the critical point.|The vapour-liquid critical point in a pressure-temperature [[phase diagram]] is at the high-temperature extreme of the liquid-gas phase boundary. <small>(The dotted green line gives the anomalous behaviour of water.)</small>]]
-''Vapour'' refers to a gas phase at a temperature where the same substance can also exist in the [[liquid]] or [[solid]] state, below the [[critical temperature]] of the substance. (For example, water has a critical temperature of 374 °C (647 K), which is the highest temperature at which liquid water can exist.) If the vapour is in contact with a liquid or solid phase, the two phases will be in a state of [[thermodynamic equilibrium|equilibrium]]. The term ''gas'' refers to a compressible fluid phase. Fixed gases are gases for which no liquid or solid can form at the temperature of the gas, such as air at typical ambient temperatures. A liquid or solid does not have to boil to release a vapour.
-Vapor is responsible for the familiar processes of [[cloud]] formation and [[condensation]]. It is commonly employed to carry out the physical processes of [[distillation]] and [[headspace technology|headspace extraction]] from a liquid sample prior to [[gas chromatography]].
-The constituent [[molecule]]s of a vapor possess vibrational, rotational, and translational motion. These motions are considered in the [[kinetic theory of gases]].
-==Vapour pressure==
-{{Main|Vapour pressure}}
 [[File:Binary_Boiling_Point_Diagram_new.svg|left|thumb|Liquid-Vapour Equilibrium]]
 The [[vapour pressure]] is the equilibrium pressure from a liquid or a solid at a specific temperature.  The equilibrium vapour pressure of a liquid or solid is not affected by the amount of contact with the liquid or solid interface.
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 *[[Earth's atmosphere|Atmospheric]] [[water vapour]] is found near the earth's surface, and may condense into small liquid droplets and form meteorological phenomena such as [[fog]], [[mist]] and [[haar (fog)|haar]].
 *[[Mercury-vapour lamp]]s and [[sodium vapour lamp]]s produce light from atoms in [[excited state]]s.
+--[[Special:Contributions/86.96.226.18|86.96.226.18]] ([[User talk:86.96.226.18|talk]]) 16:54, 20 February 2013 (UTC)
 ==Measuring vapour==
-Since it is in the gas phase, the amount of vapour present is quantified by the [[partial pressure]] of the gas. Also, vapours obey the [[barometric formula]] in a gravitational field just as conventional atmospheric gases do.
+Since it is in the g--[[Special:Contributions/86.96.226.18|86.96.226.18]] ([[User talk:86.96.226.18|talk]]) 16:54, 20 February 2013 (UTC)--[[Special:Contributions/86.96.226.18|86.96.226.18]] ([[User talk:86.96.226.18|talk]]) 16:54, 20 February 2013 (UTC)--[[Special:Contributions/86.96.226.18|86.96.226.18]] ([[User talk:86.96.226.18|talk]]) 16:54, 20 February 2013 (UTC)as phase, the amount of vapour present is quantified by the [[partial pressure]] of the gas. Also, vapours obey the [[barometric formula]] in a gravitational field just as conventional atmospheric gases do.
 == Vapours of flammable liquids ==
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 [[yi:פארע]]
 [[zh:蒸氣]]
+סباص{{Polytonic|<references />}}

v t e States of matter (list)
State	Solid Liquid Gas / Vapor Supercritical fluid Plasma
Low energy	Bose–Einstein condensate Fermionic condensate Degenerate matter Quantum Hall Rydberg matter Strange matter Superfluid Supersolid Photonic molecule
High energy	QCD matter Quark–gluon plasma Color-glass condensate
Other states	Colloid Crystal Liquid crystal Time crystal Quantum spin liquid Exotic matter Programmable matter Dark matter Antimatter Magnetically ordered Antiferromagnet Ferrimagnet Ferromagnet String-net liquid Superglass
Phase transitions	Boiling Boiling point Condensation Critical line Critical point Crystallization Deposition Evaporation Flash evaporation Freezing Chemical ionization Ionization Lambda point Melting Melting point Recombination Regelation Saturated fluid Sublimation Supercooling Triple point Vaporization Vitrification
Quantities	Enthalpy of fusion Enthalpy of sublimation Enthalpy of vaporization Latent heat Latent internal energy Trouton's rule Volatility
Concepts	Baryonic matter Binodal Compressed fluid Cooling curve Equation of state Leidenfrost effect Macroscopic quantum phenomena Mpemba effect Order and disorder (physics) Spinodal Superconductivity Superheated vapor Superheating Thermo-dielectric effect

Revision as of 16:54, 20 February 2013

Examples

Measuring vapour

Vapours of flammable liquids

See also

References