Use only 1 pound of dry ice for the demonstration of sublimation. More dry ice can produce too much steam for the sublimation process to be visible to students.
Store the dry ice in a polystyrene foam ice chest until you are ready to demonstrate. Other containers can cause issues with the dry ice, including an explosive burst.
Conduct the experiment as quickly as possible. The dry ice will continue to sublimate as it is exposed to heat in the air.
Pick up a small piece of dry ice with tongs and insert it into the opening of a balloon that has not been blown up. Knot the balloon's opening without blowing into it.
Place the balloon that you are using in the dry ice experiment into a pool of water. Wait for the sublimation process to take place so the produced gas fills the balloon. When this process is taking too long, putting the balloon into water will speed up the sublimation process.
Introduce heat to the dry ice to help speed up the sublimation process of dry ice that is not in a balloon. Heat up a spoon until it is warm, but not too hot to hold by the handle. When the bowled end of the spoon touches a small piece of dry ice, it will create a noise and melt the ice.