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Pop It! Scientific Method Materials: Bamboo skewer Petroleum jelly or vegetable oil 2 balloons Set-Up: 1. Coat the bamboo skewer with petroleum jelly or vegetable oil. 2. Place the materials in front of you. Science Time: 1. Ask a member of the audience to be your helper. 2. Have the helper blow up one balloon and tie the end in a knot. Make sure that the balloon is blown up completely. 3. Ask your helper to take the skewer and stick it through the balloon without popping it. He or she will not be able to do it. 4. Blow up the second balloon to full size, but do not make a knot. Let some air out of the balloon to reduce the size of the balloon by a third. Tie the end of the balloon in a knot. 5. Place the sharp tip of the skewer on the end of the balloon opposite the knot. 6. Spin the skewer slowly by rotating it back and forth between your fingers. Slowly apply pressure to the skewer while continuing to spin it until the tip of the skewer pierces the balloon’s surface without popping it. 7. Continue to slowly push and spin the skewer through the balloon until the sharp tip reaches the opposite side of the balloon near the knot. 8. Keep applying pressure while spinning the skewer until the tip of the skewer pierces the balloon surface on the opposite side, without popping the balloon. Tips: This trick is difficult to do the first time. You’ll probably need to practice it several times before the students. You may need to add more petroleum jelly or vegetable oil to the skewer to make sure it doesn’t burst the balloon. You can also try placing a clear piece of tape on opposite sides of the balloon. Poke the skewer through the taped areas of the balloon. Explanation: Balloons are made of rubber. You are able to pierce the balloon without it bursting because of the unique composition of rubber. Rubber is made of molecules in long chains. These long chains of molecules are linked together crosswise, similar to a screen on a screen door, to create the balloon. When your helper quickly pierces the balloon, the chains break apart and the balloon bursts. However, when you try very slowly to pierce the balloon, the chains of molecules push apart slightly, making space for the skewer to pass through. You make it easier for the skewer to pass through the chains when you blow up the balloon and then reduce its volume. Blowing up the balloon completely and then releasing the air weakens the chains of molecules in some places. This allows the skewer to pass through the balloon more easily. The petroleum jelly also helps by serving as a lubricant, which is a film like substance that reduces friction between the solid surfaces. The jelly reduces the friction between the skewer and the balloon, allowing the skewer to pass though more easily.
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