When you break the dry ice into small pieces it starts to make a cloud of carbon dioxide. But unlike smoke from a candle or fire, the dry ice smoke doesn’t float. Instead, it settles onto the ground or, in this case, on top of the dry ice. Why is that? The smoke is actually a combination of carbon dioxide gas and water vapor.
Dry ice smoke is heavier than the air around it, so it sinks in the air rather than rising. This explains why the bubbles float on top of the dry ice smoke. The air exhaled into the bubble is less dense than the gases comprising the dry ice smoke, but slightly heavier than the air surrounding the bubble. So although the bubbles don’t float in the air, they do float on the heavier dry ice smoke.
DRY ICE is extremely dangerous. ADULT SUPERVISION REQUIRED.
Handling Dry Ice
Due to its extremely cold temperature (-78.5oC, or -109.3oF), dry ice can cause damage to the skin if handled. Use tongs or insulating gloves when handling dry ice. It is also important when crushing or grinding the solid not to get any of the dust into your eyes. Wear protective goggles.
Storing and Transporting Dry Ice
Dry ice continuously sublimates as heat enters it from its surroundings. The CO2 gas that evolves must be vented from the container. Do not seal dry ice into a container except as detailed below, because an explosive bursting of the container can result. A Styrofoam (polystyrene foam) ice chest with a loose fitting lid makes a good container for transporting dry ice.