What is Sublimation (phase transition)?
[[File:Iodine-evaporating.jpg|thumb|right|200px|[[Iodine]] sublimating]] [[File:sublimation apparatus.png|thumb|right|200px|Sublimation apparatus. Water, usually cold, is circulated in cold finger to allow the desired compound to be deposited.<br />'''1''' Cooling water in '''2''' Cooling water out '''3''' Vacuum/gas line '''4''' Sublimation chamber '''5''' Sublimed compound '''6''' Crude material '''7''' External heating]] '''Sublimation''' is how a [[solid]] becomes a [[gas]] without becoming a [[liquid]] first. It happens when the particles of a solid absorb enough energy to completely overcome the force of attraction between them. Most substances can sublimate only at low [[pressure]]. Many can sublimate in [[Outer space|space]]. Sometimes [[snow]] sublimates. This is usually on sunny winter days when the air is very dry. [[Snow]] may look like it disappears on a cold sunny day, but this is not sublimation because it forms a thin layer of [[liquid]] water first. At normal [[atmospheric pressure]] on the surface of the Earth, only some compounds like [[dry ice]] (solid carbon dioxide) can go through this [[process]]. CO<sub>2</sub> changes from dry ice, a [[solid]] to a [[gas]] without being a [[liquid]]. Also [[diamond]], [[graphite]], [[iodine]], [[ammonium chloride]] and [[aluminium chloride]] sublime rather than melt at atmospheric pressure. Sublimation is technically a part of the water cycle. {{physics-stub}} {{States of matter}} [[Category:Chemical processes]] [[Category:Physics]]