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| == '''[[Ideal gas law]]''' ==
| | {{:{{FeaturedArticleTitle}}}} |
| ''by [[User:Milton Beychok|Milton Beychok]] and [[User:Paul Wormer|Paul Wormer]] (and [[User:Daniel Mietchen|Daniel Mietchen]] and [[User:David E. Volk|David E. Volk]])
| | <small> |
| | | ==Footnotes== |
| ----
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| {| class="wikitable" style="float: right;" | |
| ! Values of ''R''
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| ! Units
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| |-
| |
| | 8.314472
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| | [[Joule|J]]·[[Kelvin|K]]<sup>-1</sup>·[[Mole (unit)|mol]]<sup>-1</sup>
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| |-
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| | 0.082057
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| | [[Liter|L]]·[[atmosphere (unit)|atm]]·K<sup>-1</sup>·mol<sup>-1</sup>
| |
| |-
| |
| | 8.205745 × 10<sup>-5</sup>
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| | [[metre|m]]<sup>3</sup>·atm·K<sup>-1</sup>·mol<sup>-1</sup>
| |
| |-
| |
| | 8.314472
| |
| | L·k[[Pascal (unit)|Pa]]·K<sup>-1</sup>·mol<sup>-1</sup>
| |
| |-
| |
| | 8.314472
| |
| | m<sup>3</sup>·Pa·K<sup>-1</sup>·mol<sup>-1</sup>
| |
| |-
| |
| | 62.36367
| |
| | L·[[mmHg]]·K<sup>-1</sup>·mol<sup>-1</sup>
| |
| |-
| |
| | 62.36367
| |
| | L·[[torr]]·K<sup>-1</sup>·mol<sup>-1</sup>
| |
| |-
| |
| | 83.14472
| |
| | L·m[[Bar (unit)|bar]]·K<sup>-1</sup>·mol<sup>-1</sup>
| |
| |-
| |
| | 10.7316
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| | [[Foot (unit)|ft]]<sup>3</sup>·[[Psi (unit)|psi]]· [[Rankine scale|°R]]<sup>-1</sup>·[[lb-mol]]<sup>-1</sup>
| |
| |-
| |
| | 0.73024
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| | ft<sup>3</sup>·atm·°R<sup>-1</sup>·lb-mol<sup>-1</sup>
| |
| |}
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| The '''[[ideal gas law]]''' is the [[equation of state]] of an '''ideal gas''' (also known as a '''perfect gas''') that relates its [[Pressure#Absolute pressure versus gauge pressure|absolute pressure]] ''p'' to its [[temperature|absolute temperature]] ''T''. Further parameters that enter the equation are the [[volume]] ''V'' of the container holding the gas and the [[amount of substance|amount]] ''n'' (in [[mole (unit)|moles]]) of gas contained in there. The law reads
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| :<math> pV = nRT \,</math>
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| where ''R'' is the [[molar gas constant]], defined as the product of the [[Boltzmann constant]] ''k''<sub>B</sub> and [[Avogadro's constant]] ''N''<sub>A</sub>
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| :<math>
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| R \equiv N_\mathrm{A} k_\mathrm{B}
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| </math> | |
| Currently, the most accurate value of R is:<ref>[http://physics.nist.gov/cgi-bin/cuu/Value?r Molar gas constant] Obtained from the [[NIST]] website. [http://www.webcitation.org/query?url=http%3A%2F%2Fphysics.nist.gov%2Fcgi-bin%2Fcuu%2FValue%3Fr&date=2009-01-03 (Archived by WebCite® at http://www.webcitation.org/5dZ3JDcYN on Jan 3, 2009)]</ref> 8.314472 ± 0.000015 J·K<sup>-1</sup>·mol<sup>-1</sup>.
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| The law applies to ''ideal gases'' which are hypothetical gases that consist of [[molecules]]<ref>Atoms may be seen as mono-atomic molecules.</ref> that do not interact, i.e., that move through the container independently of each other. In contrast to what is sometimes stated (see, e.g., Ref.<ref>[http://en.wikipedia.org/w/index.php?oldid=261421829 Wikipedia: Ideal gas law] Version of January 2, 2009</ref>) an ideal gas does not necessarily consist of [[point particle]]s without internal structure, but may be formed by polyatomic molecules with internal rotational, vibrational, and electronic [[degrees of freedom]]. The ideal gas law describes the motion of the [[center of mass|centers of mass]] of the molecules and, indeed, mass centers may be seen as structureless point masses. However, for other properties of ideal gases, such as [[entropy (thermodynamics)|entropy]], the internal structure may play a role.
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| The ideal gas law is a useful approximation for calculating temperatures, volumes, pressures or amount of substance for many gases over a wide range of values, as long as the temperatures and pressures are far from the values where [[condensation]] or [[sublimation]] occur.
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| | |
| Real gases deviate from ideal gas behavior because the intermolecular attractive and repulsive forces cause the motions of the molecules to be correlated. The deviation is especially significant at low temperatures or high pressures, i.e., close to condensation. A conventional measure for this deviation is the [[Compressibility factor (gases)|compressibility factor]].
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| There are many equations of state available for use with real gases, the simplest of which is the [[van der Waals equation]].
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| === Historic background ===
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| The early work on the behavior of gases began in pre-industrialized [[Europe]] in the latter half of the 17th century by [[Robert Boyle]] who formulated ''[[Boyle's law]]'' in 1662 (independently confirmed by [[Edme Mariotte]] at about the same time).<ref name=Savidge>[http://www.ceesi.com/docs_techlib/events/ishm2003/Docs/1040.pdf Compressibility of Natural Gas] Jeffrey L. Savidge, 78th International School for Hydrocarbon Measurement (Class 1040), 2003. From the website of the Colorado Engineering Experiment Station, Inc. (CEESI).</ref> Their work on air at low pressures established the inverse relationship between pressure and volume, ''V'' = constant / ''p'' at constant temperature and a fixed amount of air. ''Boyle's Law'' is often referred to as the ''Boyles-Mariotte Law''.
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| ''[[Ideal gas law|.... (read more)]]''
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| {| class="wikitable collapsible collapsed" style="width: 90%; float: center; margin: 0.5em 1em 0.8em 0px;"
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| ! style="text-align: center;" | [[Ideal gas law#References|notes]]
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| {{reflist|2}} | | {{reflist|2}} |
| |}
| | </small> |
The Mathare Valley slum near Nairobi, Kenya, in 2009.
Poverty is deprivation based on lack of material resources. The concept is value-based and political. Hence its definition, causes and remedies (and the possibility of remedies) are highly contentious.[1] The word poverty may also be used figuratively to indicate a lack, instead of material goods or money, of any kind of quality, as in a poverty of imagination.
Definitions
Primary and secondary poverty
The use of the terms primary and secondary poverty dates back to Seebohm Rowntree, who conducted the second British survey to calculate the extent of poverty. This was carried out in York and was published in 1899. He defined primary poverty as having insufficient income to “obtain the minimum necessaries for the maintenance of merely physical efficiency”. In secondary poverty, the income “would be sufficient for the maintenance of merely physical efficiency were it not that some portion of it is absorbed by some other expenditure.” Even with these rigorous criteria he found that 9.9% of the population was in primary poverty and a further 17.9% in secondary.[2]
Absolute and comparative poverty
More recent definitions tend to use the terms absolute and comparative poverty. Absolute is in line with Rowntree's primary poverty, but comparative poverty is usually expressed in terms of ability to play a part in the society in which a person lives. Comparative poverty will thus vary from one country to another.[3] The difficulty of definition is illustrated by the fact that a recession can actually reduce "poverty".
Causes of poverty
The causes of poverty most often considered are:
- Character defects
- An established “culture of poverty”, with low expectations handed down from one generation to another
- Unemployment
- Irregular employment, and/or low pay
- Position in the life cycle (see below) and household size
- Disability
- Structural inequality, both within countries and between countries. (R H Tawney: “What thoughtful rich people call the problem of poverty, thoughtful poor people call with equal justice a problem of riches”)[4]
As noted above, most of these, or the extent to which they can be, or should be changed, are matters of heated controversy.
- ↑ Alcock, P. Understanding poverty. Macmillan. 1997. ch 1.
- ↑ Harris, B. The origins of the British welfare state. Palgrave Macmillan. 2004. Also, Oxford Dictionary of National Biography.
- ↑ Alcock, Pt II
- ↑ Alcock, Preface to 1st edition and pt III.
