Sublimation (phase transition): Difference between revisions

Revision as of 15:57, 1 December 2023

Revision as of 15:12, 3 December 2023

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2. the transition below triple point and at boiling point

(similar to boiling)

3. the transition above triple point and below melting point (yes, solid sublimes above triple point)

(also similar to evaporation)

(top left of solid in phase diagram)

(yes, solid sublimes above triple point)

- 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) -->

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

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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 °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 an [[endothermic process]]. It 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, itsublimation 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]].

== Confusions ==

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While [[vaporization]] (from liquid to gas) is divided into two types; vaporization on the surface of the liquid is called [[evaporation]]; and vaporization at the boiling point with formation of bubbles in the interior of the liquid is called [[boiling]], there is ''no'' such distinction for the solid-to-gas transition. Solid-to-gas transition is always called sublimation in both corresponding cases.

=== MisusedMisuse for chemical reaction ===

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.

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

=== Other substances ===

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

[[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}}