Sublimation (phase transition): Difference between revisions

Revision as of 17:55, 3 January 2024

Revision as of 05:39, 17 January 2024

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<!-- READ BEFORE EDIT, sublimation refers to ALL THREE CASES:

1. the transition below triple point and belowleft boilingof pointsolid-gas boundary

(similar to evaporation)

(bottom left of solid in phase diagram)

2. the transition below triple point and at boilingsolid-gas pointboundary

(similar to boiling)

3. the transition above triple point and below meltingsolid-liquid pointboundary (yes, solid sublimes above triple point)

(also similar to evaporation, just higher pressure)

(top left of solid in phase diagram)

These three cases jointly exhaust the solid space in the phrase diagram. This make sense, after all, technically, all solids sublime (depending mostly on vapour pressure, which is very situational).

- the definition is simply the transition of a substance directly from the solid to the gas state, without passing through the liquid state

- technically, all solids sublime (depending mostly on vapour pressure, which is very situational) --><!-- checking some online English dictionaries:

One may notice there is a fourth case in the solid space, that is, at the solid-liquid boundary. It is uncertain if the solid can still sublime while melting, those who know may clarify. --><!-- checking some online English dictionaries:

1. sublime and sublimate are both valid, and both have some other meanings

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https://www.dictionary.com/browse/sublime

4. sublimation seems used to mean deposition alone but this meaning is now completely obsolete, few if any online dictionary has such meaning as of 2023, the archaic use is likely phased out -->

yes, this is very confusing -->

[[File:Nickelocen an einem Kühlfinger.jpg|thumb|right|Dark green [[crystals]] of [[nickelocene]], sublimed and freshly deposited on a [[cold finger]]]]

[[File:Sublimation of iodine.webm|thumb|Sublimation of iodine]]

'''Sublimation''' is the [[Phase transition|transition of a substance]] directly from the [[solid]] to the [[gas]] state, without passing through the [[liquid]] state.<ref>{{cite book |last1=Whitten |first1=Kenneth W. |last2=Gailey |first2=Kenneth D. |last3=Davis |first3=Raymond E. |title=General chemistry |url=https://archive.org/details/generalchemistry00whit_0 |url-access=registration |date=1992 |publisher=Saunders College Publishing |isbn=0-03-072373-6 |page=[https://archive.org/details/generalchemistry00whit_0/page/475 475] |edition=4th}}</ref> The verb form of sublimation is ''sublime'', or less preferably, ''sublimate''.<ref name=":0">{{cite Merriam-Webster|Sublimate}}</ref> ''Sublimate'' also refers to the product obtained by sublimation.<ref name=":0" /><ref>[https://www.collinsdictionary.com/dictionary/english/sublimate "Sublimate"]. [[Collins English Dictionary#CollinsDictionary.com|CollinsDictionary.com Dictionary]].</ref> The reverse process of sublimation is [[deposition (phase transition)|''deposition'']] or(also called ''desublimation''), in which a substance passes directly from a gas to a solid phase, without passing through the liquid state.<ref name="DepositionDef">{{cite journal |title=Controlling condensation and frost growth with chemical micropatterns |first1=Jonathan B. |last1=Boreyko |first2=Ryan R. |last2=Hansen |first3=Kevin R. |last3=Murphy |first4=Saurabh |last4=Nath |first5=Scott T. |last5=Retterer |first6=C. Patrick |last6=Collier |journal=Scientific Reports |year=2016 |volume=6 |pages=19131 |doi=10.1038/srep19131 |pmid=26796663 |pmc=4726256 |bibcode=2016NatSR...619131B}}</ref>

All solids sublime, though most sublime at extremely low rates that are hardly detectable. At [[standard conditions for temperature and pressure|normal pressures]], most [[chemical compound]]s and [[chemical element|elements]] possess three different states at different [[temperature]]s. In these cases, the transition from the [[solid]] to the [[gas]] state requires an intermediate liquid state. The pressure referred to is the ''[[partial pressure]]'' of the substance, not the ''total'' (e.g. atmospheric) pressure of the entire system. Thus, any solid can sublime if its [[vapour pressure]] is higher than the surrounding partial pressure of the same substance, and in some cases, sublimes at an appreciable rate (e.g. water ice just below 0&nbsp;°C).

For some substances, such as [[carbon]] and [[arsenic]], sublimation from solid state is much more achievable than [[evaporation]] from liquid state and it is difficult to obtain them as liquids. This is because the pressure of their [[triple point]] in its [[phase diagram]], (which corresponds to the lowest pressure at which the substance can exist as a liquid,) is very high.

Sublimation is caused by the absorption of heat which provides enough energy for some molecules to overcome the [[intermolecular force|attractive forces]] of their neighbors and escape into the vapor phase. Since the process requires additional energy, sublimation is an [[endothermic]] change. The [[enthalpy of sublimation]] (also called heat of sublimation) can be calculated by adding the [[enthalpy of fusion]] and the [[enthalpy of vaporization]].

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The term ''sublimation'' refers specifically to a [[physical change]] of [[state of matter|state]] and is not used to describe the transformation of a solid to a gas in a chemical reaction. For example, the dissociation on heating of solid [[ammonium chloride]] into hydrogen chloride and ammonia is ''not'' sublimation but a chemical reaction. Similarly the combustion of candles, containing [[paraffin wax]], to [[carbon dioxide]] and [[water vapor]] is ''not'' sublimation but a chemical reaction with oxygen.

=== UncommonHistorical definition ===

Sublimation is sometimeshistorically used as a generic term to describe a two-step phase transition ― a solid-to-gas transition (sublimation in a more precise definition) followed by a gas-to-solid transition ([[deposition (phase transition)|deposition]]).<ref>{{Dictionary.com|Sublime}}</ref><ref>[https://www.collinsdictionary.com/dictionary/english/sublime "Sublime"]. [[Collins English Dictionary#CollinsDictionary.com|CollinsDictionary.com Dictionary]].</ref>[[File:Comparison carbon dioxide water phase diagrams.svg|thumb|upright=2|Comparison of phase diagrams of carbon dioxide (red)See and water[[Sublimation (blue)phase showing the carbon dioxide sublimation point (middle-lefttransition)#Historical at 1 atmosphere. As dry ice is heated, it crosses this point along the bold horizontal line from the solid phase directly into the gaseous phase. Water, on the other hand, passes through a liquid phase at 1 atmosphere.usage|below]])

==Examples==

[[File:Comparison carbon dioxide water phase diagrams.svg|thumb|upright=2|Comparison of phase diagrams of carbon dioxide (red) and water (blue) showing the carbon dioxide sublimation point (middle-left) at 1 atmosphere. As dry ice is heated, it crosses this point along the bold horizontal line from the solid phase directly into the gaseous phase. Water, on the other hand, passes through a liquid phase at 1 atmosphere.]]

===Carbon dioxide===

[[File:Dry Ice Vapor (17490553041).jpg|thumb|[[Dry ice]] subliming in air]]

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[[Arsenic]] can sublime readily at high temperatures.

[[Cadmium]] and [[zinc]] sublime much more than other common materials, so they are not suitable [[materials for use in vacuum]] because they sublime much more than other common materials.{{citation needed|date=May 2019}}

==Purification by sublimation==