Kids, did you ever notice that helium balloons made using a regular balloon (not a Mylar balloon), do not last very long?   This column provides a way to measure the diffusion of helium out of a balloon, and compare the results to a balloon filled with air.

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

You'll need a package of regular balloons, a helium gas source, a yardstick, and a tank of water large enough to hold a submerged balloon (a bathtub might work).   Blow up three balloons with air and three balloons with helium, all to approximately the same size.   Measure their volume by submerging each one into the tank of water, and measuring the "displacement".   This means that you'll measure the height of the water before the balloon is added, again after it is submerged, and subtract to get the result.

Then measure the heights again after predetermined amounts of time, such as every few hours, until you see no change in the measurements (the balloon has deflated).   Plot your results of water height vs. time.   The idea is to see which balloon diffuses the gas it is holding more quickly.   The answer is that, since the helium molecules are smaller than air molecules, helium should diffuse out faster.   You could also test different brands of balloons to do a comparison.

What do the results tell you about regular balloons and Mylar balloons?   Both are made of polymers, but the spaces between the individual chains of molecules (polymer chains) are quite different.   Mylar is an exceptionally strong polyester, while many regular balloons are made of latex.

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
June 2003

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Reference:   This activity came to us courtesy of Ms. Adrian Winans, who performed this as a fourth-grade science fair project.