The purpose of this experiment is to show that the volume of air in a closed system (a system where variables are constant until changed) varies with the temperature.
Dry ice or liquid nitrogen
Large coffee can
What To Do
Start with two inflated balloons, approximately the same size in circumference. Measure the circumference of each balloon at room temperature by wrapping the string around the balloon. If you are in a classroom with a blackboard, you may also wish to trace each balloon on the board. Boil water in the coffee can on the hot plate. Put one balloon in the coffee can and let it sit and start to get bigger. Leave it in the can as you do the next part of the experiment. Put the other balloon in the cooler. If using dry ice, leave it set for at least 5 minutes before measuring. If using liquid nitrogen, measure the circumference immediately following the pouring of liquid nitrogen over the balloon. Either way, measure the balloon again using the same string. Now return to the balloon that is warming up. It should appear as if the balloon is climbing out of the can because it has gotten larger. Remove the balloon from the can and immediately measure it with the same string you used before.
1. How did the circumference of the balloon placed in the boiling water change? What about the balloon in the dry ice?
2. Predict what would happen if the balloon were exposed to even colder temperatures. What about even warmer temperatures?
As the temperature increases, the volume of the air in the balloon increases. As the temperature decreases, the volume of the air in the balloon decreases. By changing temperature, the space occupied by the air (the volume of the air) changes.
"Science is Fun" in "Fundamentals of Physical Sciences." Janet Z. Tarino, The Ohio State University, 1990.
© S. Olesik, WOW Project, Ohio State University, 1999.