Why Do Spray Cans Feel Cold?

Why does a can of "compressed air" turn cold when you spray it? Most of these cans don't contain any air. One popular duster's safety data sheet lists a single ingredient, tetrafluoroethane, a liquid that boils at about -15 °F (-26 °C), colder than a home freezer, which should be at 0 °F. At a room temperature of 68 °F (20 °C), it is 83 °F above its boiling point, so when you press the button it boils, taking heat from the liquid, the can and your hand. This video also looks at other propellants, butane (boiling at about 32 °F, 0 °C) and propane (about -44 °F, -42 °C), explains the second cooling effect, a gas that cools as it spreads out, and covers how to use a duster safely. Try it yourself: ▶ https://www.metric-conversions.org/temperature/fahrenheit-to-celsius.htm ▶ https://www.metric-conversions.org/temperature-conversion.htm Chapters: 0:00 The puzzle 0:27 What's inside the can 0:56 Boiling at the button 2:03 Expanding gas 2:21 Safety and takeaway Sources: • Compressed Air Dusters and Environmental Concerns (EPA Federal Electronics Challenge): https://www.epa.gov/sites/default/files/documents/dusters.pdf • Dust-Off Special Application Compressed Gas Duster SDS (Falcon Safety Products, rev. 18 May 2015): https://www.sisweb.com/referenc/msds/dustoffsp-sds.pdf • Are You Storing Food Safely? (FDA): https://www.fda.gov/consumers/consumer-updates/are-you-storing-food-safely • Liquified vs compressed gases (BAMA, via CanTech International): https://www.cantechonline.com/feature/40559/liquified-vs-compressed-gases/ • Butane (NIST Chemistry WebBook): https://webbook.nist.gov/cgi/cbook.cgi?Name=butane&Units=SI&cTP=on • Propane (NIST Chemistry WebBook): https://webbook.nist.gov/cgi/cbook.cgi?Name=propane&Units=SI&cTP=on • 5.1: Rising Air (LibreTexts, De Anza College): https://geo.libretexts.org/Workbench/DeAnza-MET10L/05%3A_Rising_Air_and_Stability/5.01%3A_Rising_Air • Phase Changes (HyperPhysics): http://hyperphysics.gsu.edu/hbase/thermo/phase2.html • Fahrenheit to Celsius (metric-conversions.org): https://www.metric-conversions.org/temperature/fahrenheit-to-celsius.htm Is there anything else you'd like us to cover? Let us know in the comments below.