Solid carbon dioxide turning into a gas
Apparatus and materials
Polythene bag or balloons, small
Dry ice attachment
Health & Safety and Technical notes
Whether you use a gas cylinder or solid CO2, you should do a risk assessment.
Solid carbon dioxide must not be handled with bare fingers: use tongs or wear thick gloves. Wear eye protection before breaking a large block (with a hammer and cold chisel).
You may be able to locate a local supplier for solid CO2. If you have a dry ice attachment and a CO2 cylinder, follow the instructions to get about half a teaspoon of carbon dioxide snow.
For further information about dry ice, see the apparatus entry for CO2 cylinder.
If using a balloon, stretch the neck of the balloon and hold it open with several fingers whilst about half a teaspoon of carbon dioxide snow is scraped in. Quickly flatten the balloon and knot the neck firmly. A polythene bag is easier to fill but more awkward to seal well.
Solid carbon dioxide is unusual in that, at room temperature and pressure, it does not turn into a liquid before changing into a gas as it warms up – it sublimes. The change in volume from solid to gas can be seen to be as much as 600 times if the container in which it is expanding is well-sealed and has no holes.
Alternately you could place a small piece of solid carbon dioxide (say, 0.5 cm3) under the mouth of a gas jar or measuring cylinder which is full of water and inverted over a tank of water so that the bubbles of gas can be collected.
This experiment was safety-checked in January 2005