Usually the during the week of homecoming, my Biophysical Science class is just finishing up a basic chemistry unit on the properties of matter. To keep the kids focused on science, I make sure to obtain a little dry ice to have my students observe a unique phase change known as sublimation.
- Sublimation of dry ice
- Density of carbon dioxide (bubbles with hover over more dense carbon dioxide – see video)
- Carbon Dioxide as a liquid (under pressure) as it exists in a gas cylinder
- Carbon Dioxide as a liquid (by sealing off a pipette with pliers, students can safely observe carbon dioxide liquefy as the pressure increases – see phase change diagram of carbon dioxide)
- Rapid sublimation of carbon dioxide in water in a sealed Nalgene bottle (see videos below)
Note the rapid condensation that appears on the lab table once the pressure is equalized.
NOTE: this demonstration was done behind a Plexiglas screen when there were no kids in the room. Below is a picture of the bottle before, after, and a piece that was lodged in the ceiling (of which I am quite proud).
I should emphasize that this rapid buildup of gas pressure can be very dangerous. In fact, the rapid vaporization of liquid nitrogen in a sealed plastic container is exactly how I once blew up a sink (see About page). This is why a safe alternative to a live demo is to take an extreme video for future use.