Air pressure, water, and an aluminum can?

Question

ok if there was an aluminum can with a little bit of water inside of it, and it was heated (ok, obviously there is an opening at the top) where will there be the most air pressure...outside the can or inside the can?

plz explain becuz i'm sooooo confuddled!

if there is more pressure outside then answer this:

shouldn't there be more pressure on the inside because there is more movement in the molecules inside the can (it's hot)

if there is more pressure inside the can answer this:

shouldn't there be more pressure on the outside because hot air is less dense???

thanks for any answers!!

Answer 1

The pressure won't change because the top of the can is allowing the gases to escape.  The only thing that changes is the gas becomes less dense as you heat it.  

If the can was sealed and you heated it up there would be more pressure on the inside but because there is an opening at the top of the can the pressure quickly equalizes and no pressure is built up.  Density of gases are not directly related to pressure.  Atmospheric pressure is 14.7 psi which means that there is almost 15 pounds of air pushing on every single square inch of your body.  Atmospheric pressure is caused by the weight of all the air in your body being pulled in by gravity and squeezing your body.  Hope this helps.