Gas laws

Gas laws

:"This articles outlines the historical development of the laws describing ideal gases. For a detailed description of the ideal gas laws and their further development, see Ideal gas, Ideal gas law and Gas"

The gas laws are a set of laws that describe the relationship between thermodynamic temperature ("T"), absolute pressure ("P") and volume ("V") of gases. They are a loose collection of rules developed between the late Renaissance and early 19th century.

Three earlier gas laws:
* Boyle's law (1662, relating pressure and volume), P1V1=P2V2
* Charles's law (1787, relating volume and temperature)V1/T1=V2/T2, and
* Gay-Lussac's law (1809, relating temperature and pressure)P1/T1=P2/T2,were combined to form the combined gas law

:frac {P_1V_1} {T_1} = frac {P_2V_2} {T_2}.

With the addition of Avogadro's law, this developed into the
*ideal gas law :PV = nRT ,,where :"P" is the absolute pressure (SI unit: pascal):"V" is the volume (SI unit: cubic metre):"n" is the amount of substance (loosely "number of moles" of gas):"R" is the ideal gas constant (SI: 8.3145 J/(mol K)):"T" is the thermodynamic temperature (SI unit: kelvin).

(The law works with any consistent set of units, provided that the temperature scale starts at absolute zero, and the appropriate gas constant is used.)

An equivalent formulation of this law is:

:PV = kNT ,

where:"k" is the Boltzmann constant:"N" is the number of molecules.

These equations are exact only for an ideal gas, which neglects various intermolecular effects (see real gas). However, the ideal gas law is a good approximation for most gases under moderate pressure and temperature.

This law has the following important consequences:
# If temperature and pressure are kept constant, then the volume of the gas is directly proportional to the number of molecules of gas.
# If the temperature and volume remain constant, then the pressure of the gas changes is directly proportional to the number of molecules of gas present.
# If the number of gas molecules and the temperature remain constant, then the pressure is inversely proportional to the volume.
# If the temperature changes and the number of gas molecules are kept constant, then either pressure or volume (or both) will change in direct proportion to the temperature.

Other gas laws of historical importance include:

: Graham's law is an empirical relationship between the rate at which gas molecules effuse through porous barriers and molecular weight. These early molecule-based laws developed into the full kinetic theory of gases.

: Dalton's law states that the pressure of a mixture of gases simply is the sum of the partial pressures of the individual components.

See also

* Ideal gas
* Ideal gas law
* Kinetic theory

References

*
*
*


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • gas laws — Laws that relate the pressure, volume, and temperature of a gas. Boyle s law named for Robert Boyle states that, at constant temperature, the pressure P of a gas varies inversely with its volume V, or PV = k, where k is a constant. Charles s law… …   Universalium

  • gas laws — /ˈgæs lɔz/ (say gas lawz) plural noun laws, especially Boyle s law and Charles s law, which relate the pressure, volume, and temperature of a gas. The combined ideal gas law states that for 1 mole of an ideal gas the product of the pressure and… …  

  • gas laws — plural noun Chemistry the physical laws that describe the properties of gases, including Boyle s and Charles s laws …   English new terms dictionary

  • gas laws — plural n. Chemistry the physical laws that describe the properties of gases, including Boyle s and Charles laws …   Useful english dictionary

  • gas — gasless, adj. /gas/, n., pl. gases, v., gassed, gassing. n. 1. Physics. a substance possessing perfect molecular mobility and the property of indefinite expansion, as opposed to a solid or liquid. 2. any such fluid or mixture of fluids. 3. any… …   Universalium

  • Laws of science — The laws of science are various established scientific laws, or physical laws as they are sometimes called, that are considered universal and invariable facts of the physical world. Laws of science may, however, be disproved if new facts or… …   Wikipedia

  • Gas — This article is about the physical properties of gas as a state of matter. For the uses of gases, and other meanings, see Gas (disambiguation). Ga …   Wikipedia

  • Gas compressor — A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are… …   Wikipedia

  • gas constant — /ˈgæs kɒnstənt/ (say gas konstuhnt) noun the constant in the gas laws, equal to approx. 8.31 joules per kelvin mole. Also, universal gas constant …  

  • gas-expansion method —    The measurement of porosity based on the Boyle Mariotte’s gas laws [16] …   Lexicon of Cave and Karst Terminology

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”