Phase change - Revision history

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Jmdonev at 02:15, 13 July 2018

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	[[Category:Done ~~2015~~-06-01]]		[[Category:Done 2018-07-20]]
	[[File:493px-Phase change - en.svg.png\|thumb\|~~250px~~\|Figure 1: Diagram of phase transitions.<ref>Wikimedia Commons [Public Domain], Available: http://commons.wikimedia.org/wiki/File%3APhase_change_-_en.svg</ref> ]]		[[File:493px-Phase change - en.svg.png\|thumb\|400px\|Figure 1: Diagram of phase transitions.<ref>Wikimedia Commons [Public Domain], Available: http://commons.wikimedia.org/wiki/File%3APhase_change_-_en.svg</ref> ]]
			<onlyinclude>A '''phase change''' is when matter changes to from one state (solid, liquid, gas, plasma) to another. </onlyinclude> (see figure 1). These changes occur when sufficient [[energy]] is supplied to the system (or a sufficient amount is lost), and also occur when the [[pressure]] on the system is changed. The [[temperature]]s and pressures under which these changes happen differ depending on the chemical and physical properties of the system. The energy associated with these transitions is called [[latent heat]].
	<onlyinclude>A '''phase change''' is ~~a change~~ from one state ~~of [[matter]]~~ to another ~~in a thermodynamic system~~</onlyinclude>, see figure 1. These changes occur when sufficient [[energy]] is supplied to the system (or a sufficient amount is lost), and also occur when the [[pressure]] on the system is changed. The [[temperature]]s and pressures under which these changes happen differ depending on the chemical and physical properties of the system. The energy associated with these transitions is called [[~~enthalpy~~]].

	Water is a substance that has many interesting properties that influence its phase changes. Most people learn from an early age that water melts from ice to [[liquid]] at 0°C, and boils from a liquid to a [[gas]] at 100°C; but this isn't true in all circumstances. The pressure affects these transition points, so for water, the boiling point actually decreases as the pressure decreases. Water also has certain intermolecular forces which govern the temperatures at which these transitions occur.<ref>UC Davis Chem Wiki [Online] Available: http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Atomic_and_Molecular_Properties/Intermolecular_Forces/Van_der_Waals_Forces</ref> This difference in boiling point is why the directions for cooking at high altitudes are sometimes slightly different (like boiling pasta longer).		Water is a substance that has many interesting properties that influence its phase changes. Most people learn from an early age that water melts from ice to [[liquid]] at 0°C, and boils from a liquid to a [[gas]] at 100°C; but this isn't true in all circumstances. The pressure affects these transition points, so for water, the boiling point actually decreases as the pressure decreases. Water also has certain intermolecular forces which govern the temperatures at which these transitions occur.<ref>UC Davis Chem Wiki [Online] Available: http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Atomic_and_Molecular_Properties/Intermolecular_Forces/Van_der_Waals_Forces</ref> This difference in boiling point is why the directions for cooking at high altitudes are sometimes slightly different (like boiling pasta longer).

	The relatively large amount of energy needed to change the phase of water is one of the reasons why water is used to cool [[power plant]]s. It's also part of why humans sweat in order to stay cool (through evaporation) and dogs pant. This high ~~enthalpy~~ also makes water important for [[moderating the climate]].		The relatively large amount of energy needed to change the phase of water is one of the reasons why water is used to cool [[power plant]]s. It's also part of why humans sweat in order to stay cool (through evaporation) and dogs pant. This high latent heat also makes water important for [[moderating the climate]].

	Boiling and ~~condensing~~ are common ~~phase changes as are freezing and melting. These~~ pairs of phase changes ~~are the most commonly~~ experienced on Earth, ~~but~~ there are other phase changes~~, like~~ going straight from solid to ~~gaseous~~. Figure 1 also shows ~~other~~ phase changes~~, which also includes the~~ rare (on Earth, at least) ~~state of~~ [[plasma]] ~~but~~ figure 1 does not show what happens when gases or liquids get to sufficiently high pressures and temperatures that they can't be distinguished. This phase is called the [[supercritical fluid]] state (which is useful for some modern power plants).		Boiling/condensing and freezing/melting are the most common pairs of phase changes experienced on Earth. However, there are other phase changes such as [[sublimation]]—which is going straight from a solid to a gas. Figure 1 also shows phase changes that are rare (on Earth, at least) known as [[plasma]]. However, figure 1 does not show what happens when gases or liquids get to sufficiently high pressures and temperatures that they can't be distinguished. This phase is called the [[supercritical fluid]] state (which is useful for some modern power plants).

	Visit UC Davis' Chem [http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Phases_of_Matter/Phase_Transitions wiki] for more information on phase changes and other chemical phenomena.		Visit UC Davis' Chem [http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Phases_of_Matter/Phase_Transitions wiki] for more information on phase changes and other chemical phenomena.

			==For Further Reading==
			*[[Matter]]
			*[[Latent heat]]
			*[[Boiling point]]
			*[[Enthalpy]]
			*[[Supercritical fluid]]
			*[[Water cycle]]
			*Or explore a [[Special:Random\|random page]]

	==References==		==References==
	{{reflist}}		{{reflist}}
	[[Category:Uploaded]]		[[Category:Uploaded]]

J.williams: 1 revision imported

2015-08-26T21:31:29Z

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J.williams at 16:58, 12 August 2015

2015-08-12T16:58:30Z

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[[Category:Done 2015-06-01]]
[[File:493px-Phase change - en.svg.png|thumb|250px|Figure 1: Diagram of phase transitions.<ref>Wikimedia Commons [Public Domain], Available: http://commons.wikimedia.org/wiki/File%3APhase_change_-_en.svg</ref> ]]

<onlyinclude>A '''phase change''' is a change from one state of [[matter]] to another in a thermodynamic system</onlyinclude>, see figure 1. These changes occur when sufficient [[energy]] is supplied to the system (or a sufficient amount is lost), and also occur when the [[pressure]] on the system is changed. The [[temperature]]s and pressures under which these changes happen differ depending on the chemical and physical properties of the system. The energy associated with these transitions is called [[enthalpy]].

Water is a substance that has many interesting properties that influence its phase changes. Most people learn from an early age that water melts from ice to [[liquid]] at 0°C, and boils from a liquid to a [[gas]] at 100°C; but this isn't true in all circumstances. The pressure affects these transition points, so for water, the boiling point actually decreases as the pressure decreases. Water also has certain intermolecular forces which govern the temperatures at which these transitions occur.<ref>UC Davis Chem Wiki [Online] Available: http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Atomic_and_Molecular_Properties/Intermolecular_Forces/Van_der_Waals_Forces</ref> This difference in boiling point is why the directions for cooking at high altitudes are sometimes slightly different (like boiling pasta longer).

The relatively large amount of energy needed to change the phase of water is one of the reasons why water is used to cool [[power plant]]s. It's also part of why humans sweat in order to stay cool (through evaporation) and dogs pant. This high enthalpy also makes water important for [[moderating the climate]].

Boiling and condensing are common phase changes as are freezing and melting. These pairs of phase changes are the most commonly experienced on Earth, but there are other phase changes, like going straight from solid to gaseous. Figure 1 also shows other phase changes, which also includes the rare (on Earth, at least) state of [[plasma]] but figure 1 does not show what happens when gases or liquids get to sufficiently high pressures and temperatures that they can't be distinguished. This phase is called the [[supercritical fluid]] state (which is useful for some modern power plants).

Visit UC Davis' Chem [http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Phases_of_Matter/Phase_Transitions wiki] for more information on phase changes and other chemical phenomena.

==References==
{{reflist}}
[[Category:Uploaded]]