This experiment is a great one to demonstrate to large groups of kids. To them, is part magic trick and part science experiment. The kids will think that when the stick pierces the balloon, it will surely pop.
Items Needed for Experiment
- Balloon (average or large size)
- Sharp thin stick (Shish ka-bob stick works well)
Step 1: Blow up the balloon and tie off the opening.
Step 2: Take the sharp thin stick and push it through the top end of the balloon. You may need to hold the rubber around where you push in the stick if it is not very sharp.
Step 3: Keep pushing the balloon until it exits from the bottom of the balloon, near the tied off opening.
This experiment demonstrates the strength properties of the latex rubber used in the balloon. Latex rubber is extremely elastic, but has very little shear strength. When a small tear is introduced to a portion of the rubber which has a lot of tension, the material cannot handle the stress. The rubber rapidly experiences a shear failure, resulting in a balloon popping. When balloons are manufactured, the top and bottom materials are thicker than the sides. The additional thickness of latex rubber allows the stick to pierce the balloon without bursting the balloon.