Live From the Lab

In classroom lessons 7th grade students study properties of carbon dioxide in both its gaseous and solid forms. Since carbon dioxide quickly sublimes from solid to gaseous form at room temperature, the dry ice experiments are done via video conference to both 7th grade classrooms simultaneously.

The science teacher is the moderator in the classroom. Students are able to ask and answer questions from the lab teacher while watching the demonstrations. Safety issues of wearing goggles and protective gloves are reiterated.

A device constructed of PVC pipe and 2 liter bottles has water in the bottom bottle reservoir. Dry ice is dropped into the water and the gas rises up the pipes and looks like water drops exiting the bent end of the pipe. Students discuss what the "drops" are made of, and through the moderator explain what happens when the drops hit the table.

A piece of dry ice (about 10 grams) is weighed on a gram scale and the total recorded. The piece of dry ice is then placed into a deflated 9 inch balloon and the end tied off. The balloon is placed in a bowl of room temperature water. As the dry ice changes from solid to gas the balloon expands, and eventually explodes.

Students are told a gram of solid carbon dioxide equals 0.54 L of gas. The volume of a 9 inch diameter balloon is calculated. Students determine and through the moderator suggest how big a piece of dry ice will be needed to inflate the balloon without popping it. The lab teacher conducts the experiments until the correct size of dry ice is found.