When I use a can of compressed air...why does it get cold?

It's a fact. When you force an amount of a gas into a smaller space at a higher pressure it will tend to get hot. When you release it into a less confined space, it will get cool. This is the basic principle behind air-conditioning and refrigeration.

Ideal gas Law. Similar to the principle used for air conditioning. When pressure in a volume goes down, temperatire goes down. Pressure goes up, temperatire goes up.

Release gas and pressure goes down.

Simple physics. When you spray the air, you are lowering the pressure of the air still in the can, allowing it to expand, and when gases expand their temperature decreases. My physics teacher would be proud I remembered that.

Physics -- releasing pressure turns cold, increasing pressure turns hot. Ever hear of truck or car tires catching fire? It's exactly the opposite effect.

It's because of the chemicals they use in it. You can buy refillable air cans by the way. You just refill it with an air compressor. My husband bought one from Harbor Freight. They have a website also.

take a paper clip and put it in there the ice will hold it till the pressure builds up then it will shoot accrost the room into your gerbil