Thursday 30 June 2011

Crush Can

Crush Can
Difficulty: 4 out of a possible 10 easy
Materials:
  • One metal soda can (EMPTY)
  • Water in a container bigger than a soda can
  • Heat resistant gloves or tongs
  • Heating device (stove or hotplate)
  • Ice (optional)
Procedure:
1.     Put a small amount (about one tablespoon) of water in the empty soda can
2.     Heat the soda can on a hotplate (or any other heat source).
3.     Fill a large basin with cold water (adding ice would help).
4.     Once the water inside the soda can is boiling, grab the hot soda can with tongs , move it over the basin of cold water, and quickly flip it (so that the opening is inside the cold water)
5.      The soda can should quickly crumple in on itself.
If it did not work:
Try the experiment again, something went wrong. (Usually either the water in the can was not boiling hard enough, or the can was submerged too much or too little.)

Explanation:

The ideal gas law PV=nRT, where P=pressure, V=volume, n=number of moles (amount of gas molecules/atoms), R is a constant at 8.314, and T is temperature helps us answer this question. Once the soda can was sealed, the volume inside it, and the amount of gas molecules, were held constant. The temperature of the air inside the can dropped because it was originally heated up by boiling water, but then cooled by the ice water. Because the temperature dropped, and everything else was kept constant, the pressure inside of the can also dropped. The pressure OUTSIDE of the can, from normal air, remained constant. Without the inside air pressure pushing back as forcefully, the outside air pressure collapsed the can.

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