Science Experiments

Dry Ice Experiments and Bombs

Mon, 24th Aug 2009

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 -78C (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 -78C 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.

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