Monday, June 15, 2009

Penny Science Round 2

This is a fun experiment for kids to try. You will need, a penny, an eyedropper, and rubbing alcohol, and a cup of water. First, fill the eyedropper from the cup of water. See how many drops you can place on a dry penny before it spills off of the penny's side. (You will be surprised if you have never done this before. I usually get between 30 and 60 drops of water on a penny.) Next, repeat the experiment by dropping drops of rubbing alcohol from the eyedropper onto a dry penny. (You will only get around 10-20 drops.) Explain to your kids that the difference is that water is cohesive (bonds with itself) while rubbing alcohol is not. (In kid terms, "water wants to stick to other water like best friends. We call this cohesion. Rubbing alcohol does not do that because it is made of different stuff and it happens to not stick to other rubbing alcohol very well.")

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