Editing Oxygen (section)

===Physical properties===
[[File:Liquid oxygen in a beaker 4.jpg|thumb|Liquid oxygen boiling (O<sub>2</sub>)|alt=A transparent beaker containing a light blue fluid with gas bubbles.]]
{{see also|Liquid oxygen|solid oxygen}}
Oxygen [[Solubility|dissolves]] more readily in water than nitrogen, and in freshwater more readily than in seawater. Water in equilibrium with air contains approximately 1 molecule of dissolved {{chem|O|2}} for every 2 molecules of {{chem|N|2}} (1:2), compared with an atmospheric ratio of approximately 1:4. The solubility of oxygen in water is temperature-dependent, and about twice as much ({{val|14.6|u=mg/L}}) dissolves at 0&nbsp;°C than at 20&nbsp;°C ({{val|7.6|u=mg/L}}).<ref name="NBB299" /><ref>{{cite web |url=http://www.engineeringtoolbox.com/air-solubility-water-d_639.html |title=Air solubility in water |access-date=December 21, 2007 |publisher=The Engineering Toolbox |archive-date=April 4, 2019 |archive-url=https://web.archive.org/web/20190404044017/https://www.engineeringtoolbox.com/air-solubility-water-d_639.html |url-status=live}}</ref> At 25&nbsp;°C and {{convert|1|atm|lk=on|sigfig=6}} of air, freshwater can dissolve about 6.04&nbsp;[[Litre|milliliters]]&nbsp;(mL) of oxygen per [[liter]], and [[seawater]] contains about 4.95&nbsp;mL per liter.<ref>{{cite book |title = The Physiology of Fishes |first1=David Hudson |last1=Evans |last2=Claiborne |first2=James B. |page=88 |date=2005 |edition=3rd |publisher=CRC Press |isbn=978-0-8493-2022-4}}</ref> At 5&nbsp;°C the solubility increases to 9.0&nbsp;mL (50% more than at 25&nbsp;°C) per liter for freshwater and 7.2&nbsp;mL (45% more) per liter for sea water.{{cn|date=May 2025}}
{| class="wikitable" style="float:left; margin-right:2em"
|+Oxygen gas dissolved in water at sea-level<br />(milliliters per liter)
!
!5&nbsp;°C
!25&nbsp;°C
|-
|Freshwater
|9.00
|6.04
|-
|Seawater
|7.20
|4.95
|}
Oxygen condenses at 90.20&nbsp;[[kelvin|K]] (−182.95&nbsp;°C, −297.31&nbsp;°F) and freezes at 54.36&nbsp;K (−218.79&nbsp;°C, −361.82&nbsp;°F).<ref>{{cite book |first=David R. |last=Lide |title=CRC Handbook of Chemistry and Physics |edition=84th |publisher=[[CRC Press]] |location=Boca Raton, Florida |date=2003 |chapter=Section 4, Properties of the Elements and Inorganic Compounds; Melting, boiling, and critical temperatures of the elements |isbn=978-0-8493-0595-5 |url=https://archive.org/details/crchandbookofche0000unse_p1y5}}</ref> Both [[liquid oxygen|liquid]] and [[solid oxygen|solid]] {{chem|O|2}} are clear substances with a light [[diffuse sky radiation|sky-blue]] color caused by absorption in the red (in contrast with the blue color of the sky, which is due to [[Rayleigh scattering]] of blue light). High-purity liquid {{chem|O|2}} is usually obtained by the [[fractional distillation]] of liquefied air.<ref>{{cite web |url = http://www.uigi.com/cryodist.html |title = Overview of Cryogenic Air Separation and Liquefier Systems |publisher = Universal Industrial Gases, Inc. |access-date = December 15, 2007 |archive-date = October 21, 2018 |archive-url = https://web.archive.org/web/20181021010346/http://www.uigi.com/cryodist.html |url-status = live}}</ref> Liquid oxygen may also be condensed from air using [[liquid nitrogen]] as a coolant.<ref name="LOX MSDS">{{cite web |url=https://www.mathesontrigas.com/pdfs/msds/00225011.pdf |title=Liquid Oxygen Material Safety Data Sheet |publisher=Matheson Tri Gas |access-date=December 15, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20080227014309/https://www.mathesontrigas.com/pdfs/msds/00225011.pdf |archive-date=February 27, 2008 }}</ref>

Liquid oxygen is a highly reactive substance and must be segregated from combustible materials.<ref name="LOX MSDS" />

The spectroscopy of molecular oxygen is associated with the atmospheric processes of [[aurora]] and [[airglow]].<ref name="Krupenie1972">{{cite journal |last1=Krupenie |first1=Paul H. |title=The Spectrum of Molecular Oxygen |journal=Journal of Physical and Chemical Reference Data |volume=1 |issue=2 |year=1972 |pages=423–534 |doi=10.1063/1.3253101 |bibcode=1972JPCRD...1..423K |s2cid=96242703 }}</ref> The absorption in the [[Herzberg continuum]] and [[Schumann–Runge bands]] in the ultraviolet produces atomic oxygen that is important in the chemistry of the middle atmosphere.<ref name="BrasseurSolomon2006">{{cite book |author1=Guy P. Brasseur |author2=Susan Solomon |title=Aeronomy of the Middle Atmosphere: Chemistry and Physics of the Stratosphere and Mesosphere |url=https://books.google.com/books?id=Z5OtlDjfXkkC&pg=PA220 |date=January 15, 2006 |publisher=Springer Science & Business Media |isbn=978-1-4020-3824-2 |pages=220– |access-date=July 2, 2015 |archive-date=February 2, 2017 |archive-url=https://web.archive.org/web/20170202143926/https://books.google.com/books?id=Z5OtlDjfXkkC&pg=PA220 |url-status=live}}</ref> Excited-state singlet molecular oxygen is responsible for red chemiluminescence in solution.<ref name="Kearns1971">{{cite journal |last1=Kearns |first1=David R. |title=Physical and chemical properties of singlet molecular oxygen |journal=Chemical Reviews |volume=71 |issue=4 |year=1971 |pages=395–427 |doi=10.1021/cr60272a004}}</ref>

Table of thermal and physical properties of oxygen (O<sub>2</sub>) at atmospheric pressure:<ref>{{Cite book |last=Holman |first=Jack P. |url=https://www.worldcat.org/oclc/46959719 |title=Heat transfer |publisher=McGraw-Hill Companies, Inc. |year=2002 |isbn=9780072406559 |edition=9th |location=New York, NY |pages=600–606 |language=English |oclc=46959719}}</ref><ref>{{Cite book |last=Incropera 1 Dewitt 2 Bergman 3 Lavigne 4 |first=Frank P. 1 David P. 2 Theodore L. 3 Adrienne S. 4 |url=https://www.worldcat.org/oclc/62532755 |title=Fundamentals of heat and mass transfer. |publisher=John Wiley and Sons, Inc. |year=2007 |isbn=9780471457282 |edition=6th |location=Hoboken, NJ |pages=941–950 |language=English |oclc=62532755}}</ref>
{|class="wikitable mw-collapsible mw-collapsed"
|[[Temperature]] (K)
|[[Density]] (kg/m<sup>3</sup>)
|[[Specific heat]] (kJ/(kg·K))
|[[Dynamic viscosity]] (kg/(m·s))
|[[Kinematic viscosity]] (m<sup>2</sup>/s)
|[[Thermal conductivity]] (W/(m·K))
|[[Thermal diffusivity]] (m<sup>2</sup>/s)
|[[Prandtl Number]]
|-
|100
|3.945
|0.962
|7.64E-06
|1.94E-06
|0.00925
|2.44E-06
|0.796
|-
|150
|2.585
|0.921
|1.15E-05
|4.44E-06
|0.0138
|5.80E-06
|0.766
|-
|200
|1.93
|0.915
|1.48E-05
|7.64E-06
|0.0183
|1.04E-05
|0.737
|-
|250
|1.542
|0.915
|1.79E-05
|1.16E-05
|0.0226
|1.60E-05
|0.723
|-
|300
|1.284
|0.92
|2.07E-05
|1.61E-05
|0.0268
|2.27E-05
|0.711
|-
|350
|1.1
|0.929
|2.34E-05
|2.12E-05
|0.0296
|2.90E-05
|0.733
|-
|400
|0.962
|1.0408
|2.58E-05
|2.68E-05
|0.033
|3.64E-05
|0.737
|-
|450
|0.8554
|0.956
|2.81E-05
|3.29E-05
|0.0363
|4.44E-05
|0.741
|-
|500
|0.7698
|0.972
|3.03E-05
|3.94E-05
|0.0412
|5.51E-05
|0.716
|-
|550
|0.6998
|0.988
|3.24E-05
|4.63E-05
|0.0441
|6.38E-05
|0.726
|-
|600
|0.6414
|1.003
|3.44E-05
|5.36E-05
|0.0473
|7.35E-05
|0.729
|-
|700
|0.5498
|1.031
|3.81E-05
|6.93E-05
|0.0528
|9.31E-05
|0.744
|-
|800
|0.481
|1.054
|4.15E-05
|8.63E-05
|0.0589
|1.16E-04
|0.743
|-
|900
|0.4275
|1.074
|4.47E-05
|1.05E-04
|0.0649
|1.41E-04
|0.74
|-
|1000
|0.3848
|1.09
|4.77E-05
|1.24E-04
|0.071
|1.69E-04
|0.733
|-
|1100
|0.3498
|1.103
|5.06E-05
|1.45E-04
|0.0758
|1.96E-04
|0.736
|-
|1200
|0.3206
|1.0408
|5.33E-05
|1.661E-04
|0.0819
|2.29E-04
|0.725
|-
|1300
|0.296
|1.125
|5.88E-05
|1.99E-04
|0.0871
|2.62E-04
|0.721
|}