Editing Dry ice (section)

==Properties==
{{For|supplementary chemical data|Carbon dioxide data}}
[[File:Comparison carbon dioxide water phase diagrams.svg|thumb|350px|Comparison of [[phase diagram]]s of carbon dioxide (red) and water (blue) as a log-lin chart with phase transitions points at 1{{nbsp}}[[Standard atmosphere (unit)|atmosphere]] pressure]]

Dry ice is the solid form of [[carbon dioxide]] (CO<sub>2</sub>), a molecule consisting of a single [[carbon]] atom [[covalent bond|bonded]] to two [[oxygen]] [[atom]]s. Dry ice is colorless, odorless, and non-flammable, and can lower the [[pH]] of a solution when dissolved in [[water]], forming [[carbonic acid]] (H<sub>2</sub>CO<sub>3</sub>).<ref name="Yaws 2001 p=125">{{Harvnb|Yaws|2001|p=125}}</ref>

At pressures below 5.13 [[Atmosphere (unit)|atm]] and temperatures below<!--Look at the phase diagram before changing this to "above", "below" might be counterintuitive, but is correct.--> {{convert|-56.4|C|K F|}} (the [[triple point]]), CO<sub>2</sub> changes from a solid to a gas with no intervening liquid form, through a process called [[Sublimation (chemistry)|sublimation]].{{efn|''Above'' the triple point, CO<sub>2</sub> goes through the more familiar transitions via a liquid phase.}} The opposite process is called [[Deposition (phase transition)|deposition]], where CO<sub>2</sub> changes from the [[gas]] to [[solid]] phase (dry ice). At atmospheric pressure, sublimation/deposition occurs at {{convert|194.7|K|C F}}.<ref>{{Cite journal|last=Barber|first=C R|date=March 1966|title=The sublimation temperature of carbon dioxide|url=https://iopscience.iop.org/article/10.1088/0508-3443/17/3/312|journal=British Journal of Applied Physics|language=en|volume=17|issue=3|pages=391–397|doi=10.1088/0508-3443/17/3/312|bibcode=1966BJAP...17..391B|issn=0508-3443|access-date=2020-11-15|archive-date=2021-06-29|archive-url=https://web.archive.org/web/20210629110924/https://iopscience.iop.org/article/10.1088/0508-3443/17/3/312|url-status=live}}</ref>

The [[density]] of dry ice increases with decreasing temperature and ranges between about {{convert|1.55|and|1.7|g/cm3|lb/cuft|0|abbr=on}} below {{convert|195|K|C F}}.<ref>{{cite journal |last1=Mangan |first1=T.P. |last2=Salzmann |first2=C.G. |last3=Plane |first3=J.M.C. |last4=Murray |first4=B.J. |title={{CO2}} ice structure and density under Martian atmospheric conditions |journal=Icarus |date=September 2017 |volume=294 |pages=201–208 |doi=10.1016/j.icarus.2017.03.012|bibcode=2017Icar..294..201M |doi-access=free }}</ref> The low temperature and direct sublimation to a gas makes dry ice an effective [[coolant]], since it is colder than [[ice|water ice]] and leaves no residue as it changes state.<ref>{{Harvnb|Yaws|2001|p=124}}</ref> Its [[enthalpy of sublimation]] is 571 kJ/kg (25.2 kJ/mol, 136.5 calorie/g).

Dry ice is [[Chemical polarity#Nonpolar molecules|non-polar]], with a [[Dipole#Molecular dipoles|dipole moment]] of zero, so attractive [[Intermolecular force|intermolecular]] [[van der Waals force]]s operate.<ref>{{Harvnb|Verma|Khanna|Kapila|2008|p=161}}</ref> The composition results in low [[Thermal conduction|thermal]] and [[Electrical resistivity and conductivity|electrical conductivity]].<ref>{{Harvnb|Verma|Khanna|Kapila|2008|p=163}}</ref>