Have you ever stuck a balloon to a wall without the use of tape? Today we will investigate the powers of static electricity.
Materials
• Balloon
• Ground pepper
• Salt
Optional: Paper tissue bits, wool cloth, Saran wrap, cellophane tape, PVC pipe, aluminum foil bits
Experiment
Blow up a balloon and tie it off. Mix together some salt and pepper on a plate. Rub the balloon against your hair for about 10 seconds. On a dry day, you will probably notice that your hair starts to become attracted to the balloon. Now bring the balloon close to a wall. What do you notice? Rub the balloon against your hair again and then hover the balloon above the salt and pepper mixture. Does anything happen?
What’s happening?
All matter, which is everything around us, consists of atoms that are in turn made up of protons, neutrons, and electrons. When chemistry happens in the interactions of different kinds of matter, it is typically due to the negatively charged electrons that get moved around. That’s what is happening here. As you rub the balloon on your hair, the balloon pulls electrons away from your hair and gets a negative charge, leaving your hair with a net positive charge. (It now has more positively charged protons than electrons.) When the balloon is moved next to the wall, it sticks to the wall because the balloon’s negative charge repels electrons in the wall, causing them to move toward the inside and leaving behind a small, positively charged surface area. The negatively charged balloon is attracted to the positive area on the wall and sticks to it. A similar thing happens with the salt and pepper mixture, but only the pepper moves toward the balloon because it is much lighter than the salt.
This buildup of excess electrons on the surface of the balloon and the resulting attraction for a positively charged material is called static electricity. (It is static because the electrons are at rest on the surface of an object and do not flow through a conductor to form a complete circuit.)
What makes some materials become negatively charged and others positively charged when they are rubbed together? It depends on which material is more likely to give up electrons. The tendency of a material to give up electrons in contact (friction) with another material is described by the triboelectric series. Materials that are far apart in this series are likely to produce static electricity through contact. You can discover where materials are ranked in the triboelectric series by rubbing the balloon (made of synthetic rubber) with the optional items listed in the Materials section.
Place the balloon next to a small stream of running water from the faucet. Where does water belong in the triboelectric series? Another test for the triboelectric series is to stick cellophane tape to something, quickly tear it off., and then bring the tape close to other items, such as your skin, aluminum foil, tissue paper, etc.
References
To view more “ChemShorts for Kids” activities, go to:
https://chicagoacs.org/ChemShorts
