What you Need
Something you will have probably seen in every cheesy film involving anything slightly scientific is bubbling pots producing huge quantiites of smoke. These all use dry ice, that is CO2 cooled below its sublimation point of -78°C (194K). This causes it to crystallise directly to form a solid known as dry ice.
If you put this very cold solid in water it rapidly heats up above -78°C and sublimes straight back to being a gas. This warms up to room temperature very quickly and expands by a factor of 750.
If the dry ice is put into warm water, the water evaporates on the surfaces of the bubbles forming water vapour. When this meets the cold carbon dioxide gas it condenses forming billions of tiny water droplets which make up a small cloud.
Because this cloud is in carbon-dioxide, and as gas denser than air, it sinks. So it can form a cloud sitting on the floor, an effect often used theatrically on stage.
It is possible to use the expansion of dry ice as it boils and a strong pressure vessel to produce what is known as a dry ice bomb. This works on the same principle as the Liquid nitrogen bomb we did a few months ago.
These are very very dangerous, they are extremely violent and go off very quickly. Do not even think of doing this at home.
Dr Hal demonstrated this by putting a lot of dry ice in a lemonade bottle. He then added lots of boiling water to supply it with plenty of heat, put the bottle behind a blast shield and screwed on the lid.
The dry ice keeps subliming producing carbon-dioxide gas and the pressure builds up. Despite a lot of the gas dissolving in the water eventually the pressure builds up enough to make the bottle fail. Lemonade bottles are very strong and often fail at over 10 atmospheres, so the resulting explosion is very violent.
What to do
What may happen
Why does it happen?