How is Dry Ice Made?

Question

Interesting that while melting, dry ice goes directly from solid to gas...bypassing the liquid state. So, is there a liquid state during manufacture? Or does it go from carbon dioxide gas straight to solid ice? What?

Answer 1

The Web's leading source of Information about Dry Ice is at this site.

http://www.dryiceinfo.com/science.htm

Answer 2

Basically, dry ice is frozen carbon dioxide (CO2). CO2 is usually found as a gas -- it's what we exhale. To make dry ice, CO2 is compressed, and it liquefies at a pressure of approximately 870 pounds per square inch. The dry ice press then reduces the pressure, and part of the liquid CO2 sublimates (meaning it turns from a solid into a gas). The remaining liquid freezes into flakes that are compacted into solid blocks. The resulting dry ice is denser, heavier, and colder than ice made from water.

Answer 3

Basically, dry ice is frozen carbon dioxide (CO2). CO2 is usually found as a gas -- it's what we exhale. To make dry ice, CO2 is compressed, and it liquefies at a pressure of approximately 870 pounds per square inch. The dry ice press then reduces the pressure, and part of the liquid CO2 sublimates (meaning it turns from a solid into a gas). The remaining liquid freezes into flakes that are compacted into solid blocks. The resulting dry ice is denser, heavier, and colder than ice made from water.

Answer 4

FYI:
CO2 can be stored as a liquid at high pressure, such as in CO2 cartridges that power paintball guns.

Here's a quote from Wikipedia's Carbon Dioxide page:
http://en.wikipedia.org/wiki/Carbon_Dioxide
"Carbon dioxide is the most commonly used compressed gas for pneumatic systems in Combat Robots. Carbon dioxide is ideal for this application because at room temperature it becomes a liquid at a pressure of 60 bar. A tank of liquid carbon dioxide provides a constant 60 bar pressure until the tank is close to being empty. A tank of compressed air would gradually reduce in pressure as it was used."

If you want to change CO2 from one state to another, you can change the temperature or the pressure and the state will change. High pressure favors the liquid/solid states. High temperature favors the gaseous state. The actual state you observe is a function of both temperature and pressure. In practice, you could compress a gas until it is nearly liquid and then refrigerate it to finish the phase transition. Water too can bypass the liquid state and go directly to a gas at low temperatures and atmospheric pressure. You can find this information by looking at a phase diagram for the substance of interest.

A refrigerator works by compressing a gas into a liquid, causing it to heat up due to the work performed on it and the energy of condensation. If you allow the hot liquid to bleed off heat to the surroundings, (the coils in the back of the fridge do this) you now have a pressurized, relatively tepid liquid. Next you allow the gas to expand to a lower pressure and evaporate--this causes the gas to cool immensely because of evaporation (and the Joule-Thompson effect). You pump this cold gas through the interior of the fridge and it will cool the interior. The net process moves heat from the interior of the fridge to the external environment and takes more energy to perform than is transfered.

Answer 5

Carbon Dioxide is compressed into a solid under pressure.

Answer 6

you take a piece of ice, and take a blowdryer, and turn it on HIGH and dry it :)