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Sunday, February 8, 2015

What is Dry Ice?

Dry ice is nothing but solidified Carbon Dioxide (CO2). When Carbondioxide is cooled to a very low temperature it transforms into solid. The  temperature is about -78 deg centigrade. 

Carbon Dioxide is an interesting material because, at normal atmospheric pressures, it has no liquid state. It can only obtain a liquid state under very high pressure in a containment vessel.

So, when you have a frozen chunk of carbon dioxide out in the open where you can see it, it will transform directly from its solid state to a gas state with no intermediate liquid state. This process is known as 'sublimation'.

Dry ice freeze water vapor in the air near it producing visible vapor all by itself, however adding water will also add substantial heat which will cause the solid CO2 to sublimate at a greatly accelerated rate thus producing much more visible vapor.