Everything about Vapor totally explained
Vapor or
vapour (see
spelling differences) is the
gas phase component of another state of matter (for example liquid or solid) which doesn't completely fill its container. It is distinguished from the pure
gas phase by the presence of the same substance in another state of matter. Hence when a liquid has completely evaporated, it's said that the system has been completely transformed to the gas phase.
Properties
Vapor refers to a gas phase in a state of
equilibrium with identical matter in a
liquid or
solid state below its
boiling point. 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 doesn't have to boil to release a vapor. The
atmospheric boiling point of a liquid is the
temperature at which the
vapor pressure is equal to one
atmosphere (unit).
See the article on vapor pressure for more information on this topic.
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 extraction from a liquid sample prior to
gas chromatography.
The
vapor pressure is the equilibrium pressure from a liquid or a solid at a specific temperature. The equilibrium vapor pressure of a liquid or solid isn't affected by the amount of contact with the liquid or solid interface.
The
physical chemistry behind
distillation is based on manipulating the
equilibrium occurring between the liquid and vapor phases of a molecule in
solution.
For two-phase systems (for example, two liquid phases), the vapor pressure of the system is the sum of the vapor pressures of the two liquids. In the absence of stronger inter-species attractions between like-like or like-unlike molecules, the vapor pressure follows
Raoult's Law, or the vapor pressure is equal to the sum of the product of the vapor pressure of the pure compound and its mole fraction in the mixture for all of the constituents.
The constituent
atoms or
molecules of a vapor possess vibrational, rotational, and translational motion. More information can be found under the entry of the
Kinetic theory of gases.
Examples
- Perfumes contain chemicals that vaporize at different temperatures and at different rate in scent accords known as notes.
- Fog, mist and haar are meteorological designations for visible near surface water vapor.
Measuring vapor
Since it's in the gas phase, the amount of vapor present is quantified by the
partial pressure of the gas. Also, vapors obey the
barometric formula in a gravitational field just as conventional atmospheric gases do.
Vapors of flammable liquids
Flammable liquids don't burn when ignited. It is the vapor cloud above the liquid that will burn if the vapor's concentration is between the lower
explosive limit and upper explosive limit of the flammable liquid.
Further Information
Get more info on 'Vapor'.
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