OH! My science fair project was the easiest thing in the world ... and most people thought it was going to win! It didn't, and now it is pretty standard to do in several classrooms, but I just tossed in a variable and then it's different again! (My mom was a teacher -- she taught me how to procrastinate. That is why it was important that it be quick, easy, and painless. That is also why it came out looking so good that people thought it was going to win! Hooray for Mom!)
Anyway, I called it "Puddles on Pennies." Take an eyedropper, and drop bits of water on a penny to see how much it will hold. The molecules bond together causing a bubble to form on top. Do several and take averages. To ensure that it was controlled I cleaned all of the pennies in Ajax prior to the experiment. So, after doing ten or so pennies like this, I added detergent to the water to see what effect it would have on amount of water drops that would fit on the penny. Then I did the experiment with vinegar. I did the last experiment with olive oil. So easy, and so fun! It's also nice because you can set it up at the science fair to allow other kids to try it.
PM me if you have any questions!