Why Do Compressed Air Cans Get Cold?

Thanks to http://brilliant.org/minutephysics for supporting MinutePhysics - get 20% a premium subscription at http://brilliant.org/minutephysics Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics Link to Patreon Supporters: http://www.minutephysics.com/supporters/ This video is about compressed air cans (aka gas dusters) and why they get cold when you spray them. They cool off because the refrigerant inside (1,1-difluoroethane) is under pressure and boils off when the pressure lowers, and energy lost to the latent heat of vaporization cools the can a lot. Difluoroethane normally boils at -25°C (-13°F), but under ~6 atm (6 bar, 600 kpa) it is a liquid at room temperature. The gas also cools off slightly due to the Joule-Thompson effect of fluid expansion through a throttled valve. Difluoroethane is heavier than air and water soluble, so it is recommended to use it in a ventilated environment to clean your keyboard, etc. Also, 1,1-difluoroethane is a potent greenhouse gas. It is also known as Freon 152a, Ethylidene difluoride, Ethylidene fluoride, HFC-152a, R-152a, and DFE. Thanks to Tino and Hannah! REFERENCES CRC Air Duster Safety Data Sheet http://docs.crcindustries.com/msds/5185.pdf Latent Heat of vaporization https://en.wikipedia.org/wiki/Latentheat 1,1-difluoroethane chemical and physical properties https://webbook.nist.gov/cgi/cbook.cgi?ID=C75376&Mask=3FFF 1,1-difluoroethane on wikipedia https://en.wikipedia.org/wiki/1,1-Difluoroethane Free Expansion of Real Gases, Goussard, 1993 http://dx.doi.org/10.1119/1.17417 Joule-Thompson Expansion Course Notes http://tccc.iesl.forth.gr/education/local/Labs-PC-II/JT.pdf Properties of 1,1-difluoroethane http://www.inchem.org/documents/sids/sids/75376.pdf https://pubchem.ncbi.nlm.nih.gov/compound/11-difluoroethane Medical Effects of difluoroethane https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+5205 MinutePhysics is on twitter - @minutephysics And facebook - http://facebook.com/minutephysics And Google+ (does anyone use this any more?) - http://bit.ly/qzEwc6 Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute! Created by Henry Reich

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