Tuesday, February 8, 2011

Scaredy-cat toothpicks


More fun with surface tension (one of Jr scientist A's new favorite phrases). We did an experiment showing that floating toothpicks will run in terror from soap. We arranged the toothpicks in a bowl of water so that they formed a complete enclosure - this helps them keep their relative position. You need to make sure that every toothpick, including the last one, is above another toothpick on one end and below another toothpick on the other. Then we covered the end of a new toothpick in dish detergent and gently put the soapy end into the water in the middle of the other toothpicks. Instantly the floating toothpicks moved away from the center, scattering to the edges of the bowl. A fun experiment that has a big "wow" effect, is easy to re-set up (just wash the toothpicks and bowl and refill with new water), and with a little guidance, can be a hands-on experiment for a little tyke. Now Jr. scientist A keeps asking me to do that experiment again!

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