Let's have a game with boats and see how they like surface tension. We have some thin cardboard, and will use it to make boats. Just cut out the shape of the bottom of a boat, so that the boat is about one inch wide and two inches long. When your boats are made, come up front and the teacher (or aide) will run a thin line of airplane glue along the stern (rear) end of your boats. (Airplane glue is not for use by children.)

Put the boats into the water you have in your plates. The glue reduces the surface tension behind the boats. It can be seen more clearly if you sprinkle a little talcum powder on the water.

Let's cut some more boats, and put a slot in the stern so that we can re-fuel when the glue no longer has effect. We can use rubbing alcohol, a sliver of soap, a line of
detergent, or a little piece of gum camphor. We can have races!!!

Let's make more boats, and cut slots running in different directions. Maybe it will cause the boats to move differently.

We can try it with toothpick boats, with a spot of glue at one end, also. We'll call them "canoes."

Have any of you ever seen logs floated down a river to the sawmill? They tie a few together to make sort of a boat shape, then they put many logs into the inside of the shape, tie on a log or two to make the stern and let them float with the current. Let's do that with toothpicks on our water plates. Of course, we don't need to tie them together, because there is no danger of running into a ship or a houseboat, so we'll just put ten or twelve toothpicks onto the water on one side of the plate and blow on the surface of the water to make a current, and all the tooth-picks will float to the other side. Right?

Wrong. Wow! These toothpicks don't like each other much-- look at that! They don't want to stay together at all.
Why do think that is?