DryiceInfo

Dry Ice Science

PHYSICAL DESCRIPTION
Dry Ice is frozen carbon dioxide, a normal part of our earth’s atmosphere. It is the gas that we exhale during breathing and the gas that plants use in photosynthesis. It is also the same gas added to water to make soda water. Dry ice is beneficial for freezing and keeping things frozen because of its frigid temperature: -109.3°F or -78.5°C. Dry ice is widely used because it is simple to freeze and easy to handle using insulated gloves. Dry ice changes directly from a solid to a gas -sublimating – in normal atmospheric conditions without going through a wet liquid stage. For more information on carbon dioxide, see Wikipedia.

HOW DRY ICE IS MADE
The first step in making dry ice is to compress carbon dioxide gas until it liquefies, at the same time removing the excess heat. The C02 gas will liquefy at a pressure of approximately 870 pounds per square inch at room temperature. Next, the pressure is reduced over the liquid carbon dioxide by sending it through an expansion valve into an empty chamber. The liquid will flash, with some turning into gas, causing the remainder to cool. As the temperature drops to -109.3°F, the temperature of frozen CO2, some will freeze into dry ice snow. This dry ice snow is compressed together under a large press to form blocks or extruded into various sized pellets. Dry ice is much heavier than traditional ice, weighing about double.

DRY ICE MAKERS
Dry ice machines are available in all sizes and use liquid CO2. Hand-held ones make soft dry ice that dissipates quickly. Large commercial machines use hydraulic presses to compress the dry ice snow with up to 60 tons of pressure. It can produce a 55-pound block in under 60 seconds.

OTHER INTERESTING SITES

How to Make Dry Ice

Experimenting with Dry Ice
Brian Rich’s “The Saturday Scientist” has lots of fun projects, including a singing spoon and popping film cans.

FUN THINGS TO DO WITH DRY ICE! From Five Marys Farms

Cool Dry Ice Projects
14 Experiments With Solid Carbon Dioxide

An interesting Blog: Dry Ice: Environmental Friend or Foe?