This activity adapted from experiment in "Balloons, Full of Holes!"
The balloon on the left is filled with air. The balloon on the right is filled with helium. Helium
escapes through the tiny holes in the balloon membrane in the form of bubbles.
The study of membranes is important for understanding a wide range of physical, chemical and
biological systems. The word membrane to mean a sheet-like object, an object with area but very
little or no thickness. Good examples are sheets of paper or a piece of plastic food wrap. Just
like surfaces, membranes can be flat or curved; rough or smooth. Soap bubbles and all cell surfaces
like skin are other common membranes.
Language with Science
membrane surface  molecule gas
Things you will need
access to room temperature and hot water
access to a refrigerator
What to do
Want to do more?
- Ask students to predict how long a balloon with air in it will stay inflated. How about a balloon
filled with helium? Some students may have prior experience with helium balloons losing volume. Ask them
why they think that this happens.
- Fill several balloons with air and several balloons with helium (small canister from hobby shop or filled at
a party shop)
- Observe the balloons at the start, one hour, four hours, overnight.
- Ask the students for any new ideas to explain their observations. Explain that helium and air are both made
from molecules. These molecules have different properties. Helium molecules are lighter than air molecules.
Air molecules are larger than helium molecules. Could Helium
molecules be escaping? If so, how?
- Tie strings and tie weights to one air and one helium balloon.
- Put the two weighted balloons in the water tank so that they are completely submerged.
- Observe the balloons at the start, 20 min, 40 min, 60 min, 90 min, 120min, overnight.
Try testing the effect of temperature. Put the balloons in the refrigerator. Use hot water instead of cold
water in the tank. Older students might enjoy these links:Balloons, Full of Holes! (grades 2-5)
Membranes (grades 4+)