Sublimation (phase transition): Difference between revisions

Revision as of 06:17, 25 November 2023

Revision as of 07:19, 1 December 2023

Line 3:

{{distinguish|subliminal stimuli}}

{{pp|small=yes}}

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

1. the transition below triple point and below boiling point (similar to evaporation) (bottom left of solid in phase diagram)

2. the transition below triple point and at boiling point (similar to boiling)

3. the transition above triple point and below melting point (also similar to evaporation) (top left of solid in phase diagram) (yes, solid sublimes above triple point)

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

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

'''Sublimation''' is the [[Phase transition|transition of a substance]] directly from the [[solid]] to the [[gas]] state,<ref>{{cite Merriam-Webster|Sublimate}}</ref> 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> Sublimation is an [[endothermic process]] that occurs at temperatures and pressures below a substance's [[triple point]] in its [[phase diagram]], which corresponds to the lowest pressure at which the substance can exist as a liquid. All solids sublime, though many sublime at extremely low rates that are hardly detectable. The reverse process of sublimation is [[deposition (phase transition)|deposition]] or desublimation, in which a substance passes directly from a gas to a solid phase.<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> Sublimation has also been used as a generic term to describe a solid-to-gas transition (sublimation) followed by a gas-to-solid transition ([[deposition (phase transition)|deposition]]).<ref>{{Dictionary.com|Sublime}}</ref>

While [[vaporization]] (from liquid to gas) is divided into two types, that occurs as [[evaporation]] fromon the surface if it occurs below the boiling point of the liquid, and as [[boiling]] at the boiling point with formation of bubbles in the interior of the liquid if it occurs at the boiling point, there is no such distinction for the solid-to-gas transition which always occurs as sublimation from thein surfaceboth corresponding cases.

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 [[gaseous 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 sublimate if its [[vapour pressure]] is higher than the surrounding partial pressure of the same substance, and in some cases sublimates at an appreciable rate (e.g. water ice just below 0&nbsp;°C). For some substances, such as [[carbon]] and [[arsenic]], sublimation is much easier than [[evaporation]] from the melt, because the pressure of their [[triple point]] is very high, and it is difficult to obtain them as liquids.

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.

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, it 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]].

Line 24 ⟶ 32:

===Naphthalene===

[[Naphthalene]], an organic compound commonly found in pesticides such as [[mothball]]s, sublimes easily because it is made of non-polar molecules that are held together only by [[Van der Waals force|van der Waals]] intermolecular forces. Naphthalene is a solid that sublimes readily at [[standard conditions for temperature and pressure|standard atmospheric temperature]]<ref>

{{cite book

|last=Caroll |first=J.

Line 31 ⟶ 39:

|isbn=9780128005750

|page=16

}}</ref> with the boiling point (sublimation point) at around 80{{nbsp}}°C or 176{{nbsp}}°F.<ref>

{{cite web

|author=Staff writer(s)

Line 51 ⟶ 59:

[[File:Crystal-like sublimated naphthalene.jpg|thumb|Solid compound of [[naphthalene]] sublimed to form a crystal-like structure on the cool surface.]]

===Other substancesIodine===

[[File:Camphor sublimation 1.jpg|thumb|upright|[[Camphor]] subliming in a [[cold finger]]. The crude product in the bottom is dark brown; the white purified product on the bottom of the cold finger above is hard to see against the light background.]]

[[Iodine]] sublimes and produces visible fumes on gentle heating, althoughat this[[standard isconditions abovefor the triple pointtemperature and thereforepressure|standard notatmospheric true sublimationtemperature]]. It is possible to obtain liquid iodine at atmospheric pressure by controlling the temperature at just abovebetween the melting point and the boiling point of iodine. In [[forensic science]], iodine vapor can reveal latent [[fingerprint]]s on paper.<ref>{{cite book

|last=Girard |first=James

|year= 2011

Line 64 ⟶ 72:

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

=== Other substances ===

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