Shrinking Balloons (Demonstration)
(Reference: Borislaw Bilash II, George R. Gross & John K. Koob, A Demo a Day: A Year of Chemical Demonstrations, Published by:  Flinn Scientific Inc.)
 

Charles’ Law
 

Purpose:
Demonstrates Charles’ Law, volume of gas (V) is proportional to temperature of the gas (T)
 

Safety:
Use extreme care while handling liquid nitrogen.  Recommend wearing protective gloves when handling.  Never store liquid nitrogen with a tight fitting lid.  Chemical splash goggles should be worn while performing demonstration.
 

Materials:
500 mL N2(l)
Bananas
10 balloons
Racquet balls
Flowers
 

Procedure:
1. Pour 500 mL N2(l) into cooler
2. Have students blow up about 10 balloons
3. Don’t tell students what is in cooler
4. Ask students how many balloons they think will fit into cooler
5. Have students approach cooler one at a time and drop their balloon into the cooler.
6. Have students explain what they think is going on
7. Toss balloons out on desks and watch them inflate
 

Explanation:
When the air in the balloon is cooled it condenses thereby decreasing the air volume in the balloon, which is consistent with Charles’ Law
 

Clean-up:
Allow N2(l) to evaporate, or carefully toss across the floor of your room!
 
 

Ginger Chateauneuf, 2000.
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