I really enjoy doing demonstrations with dry ice. For those you haven’t received a shipment of Omaha Steaks, dry ice is frozen carbon dioxide and is most commonly used as a cooling agent for perishables in transit, such as frozen steaks.
If you take an ice cube out of the freezer and put it on the counter, it will warm up and melt into liquid water. If you let that water stand for some time, it will evaporate into the air, thus becoming a gas.
Frozen carbon dioxide skips the liquid phase. When exposed to air, it transforms into gaseous carbon dioxide. That’s called sublimating. You can see the fog or smoke drifting off a chunk of dry ice. If you put that piece of dry ice on the counter, it will gradually disappear as it sublimates into the air.
The fun comes when you add warm water, the sublimation speeds up dramatically causing large clouds of “fog.” You can add dish soap and generate bubbles filled with “smoke.”
Dry ice must be handled carefully. It’s extremely cold - about 110° below zero Fahrenheit. If you touch it with your bare skin it will “burn” you. Carbon dioxide is what we exhale and people can’t survive breathing it, so it’s important to avoid breathing in a lot of the gas. Also, since it continually transforms from a solid to a gas, you can not store it in a car, closed room or other confined space. If you do, you run the risk of walking into a room filled with carbon dioxide and finding yourself unable to breathe.
Dry ice is like so many things, work with it carefully and you can have a lot of fun. Ignore the warnings and you run the risk of frostbite...or worse.
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