Ask A Scientist Chemistry Archive

Question:
When you shake a can under pressure it feels cold where your hand is, why?
 carolyn p solarski

Answer 1:
You might want to ask again with a little more specific information.
How is the can pressurized (is it a soda can, hairspray, paint, etc)?
What kind of metal is it made of (aluminum, steel, etc)?  Has it been
sitting outside on a cold day? -- All these factors will make a difference.
 
Now for a guess.  If you are referring to something like hairspray then
I suspect the cooling comes because the propellant inside the can is
vaporizing where the can is getting heat from your hand.  It feels cool
because it is removing heat faster (to vaporize the propellant) than
on the parts of the can that don't have your heat and thus are at
room temperature (some 20 degrees cooler than your hand -- in Fahrenheit).
 
If this answer doesn't satisfy you, please do ask your question again
but be a little more specific about the experiment that you did.
 
By the way -- Excellent observation!  Keep it up!
Greg

P.S to previous response.
 
You might want to try your experiment with other types of cans --
spraypaint, hairspray, canned foods, soda, nearly full, nearly
empty, etc.  Which ones show the effect most strongly??
 
Why do you think it happens??