Dry ice, the common name for solid carbon dioxide, has severalproperties that make it useful- and fun. Dry ice is a solid attemperatures below -54 degrees Celcius, which makes it a usefulcooling agent for shipping perishable items or keeping food cold whencamping. More amazingly, when dry ice is heated under normalatmospheric pressure, instead of becoming a liquid (like ice meltinginto water), it directly sublimates into gas. Dropping dry ice intowarm water dramatically accelerates the rate of sublimation, and athick, low-lying fog composed mostly of chilled water vapor, suspendedin carbon dioxide enriched air will quickly result. This effect hasbeen used for theatrical and film effects for years, as well as beinga staple of Halloween punch bowls.