Dry Ice Bubbles
Dry ice is placed in the bottom of a large glass tank. When soap bubbles are blown into the tank, they float on the relatively dense layer of carbon dioxide gas in the tank. they also expand slightly.
This is a good demo to use when the density of gases is being discussed. This demo takes about five minutes to perform, but it must be set up about five minutes before you perform it so the dry ice can generate a layer of carbon dioxide gas.
There are really two reasons why the bubbles float. First of all, the carbon dioxide is denser than air even if they are the same temperature. In this case though, the CO2 is also colder, increasing its density even further. Since the bubble is mainly a layer of water, and CO2 is much more soluble in water than in air, the CO2 diffuses into the bubble more quickly than the air diffuses out, causing the bubble to expand slightly.
- large glass tank
- 2-3 pounds of dry ice
- one or two bottles of soap bubbles with plastic bubble blowers
- desk lamp (optional)
- background (optional)
- place dry ice in tank
- wait for about five minutes for the carbon dioxide gas to be generated
- have a volunteer or two blow bubbles into the tank
- bubbles will be suspended in the tank and grow slightly in size
- side lighting and a dark background improves visibility
Dry ice is very cold. It can cause frostbite. Avoid touching it, particularly if your fingers are wet.