Charles' Law

Materials

Balloon filled with Helium

Balloon filled with air (or Oxygen)

Dewer of Liquid Nitrogen

Styrofoam or other container to hold Liquid Nitrogen

Crucible Tongs to hold the balloons in the Liquid Nitrogen

Insulated Gloves

Gloves and Goggles

Procedure

One balloon is inflated with helium, another with air. The helium balloon is attached to a weight so it doesn't float away. Both balloons inserted into containers filled with liquid nitrogen. The helium balloon will shrink to a fraction of its original size, the oxygen balloon will shrink to a smaller size.

Discussion

Charles' Law predicts a fourfold decrease in the volume of a gas as it is chilled from room temperature, 20 degrees Celsius, to liquid nitrogen temperature, -196 degrees Celsius. If the gas in the balloon condenses, as oxygen gas does at -183 C, the volume change is much greater. The density of liquid oxygen at -183 C is 1.149g/ml, and that of the gas at 0 C is 1.429g/liter. Therefore, the volume of the balloon can shrink by a factor of more than 700.