Floating Paper Clip

2 paper clips
tap water
drinking glass
paper towel
1) Fill the glass with water. Unfold one paper clip to make a hook with a flat surface.
2) Prove to the girls that paper clips don't normally float, drop a paper clip into the cup.
3) Pull the paper clip out of the water and dry it. Lace a paper clip horizontally on the hook you made. Holding the paper clip level, lower the paper clip into the water. If it doesn't float after step 3, try rubbing the paper clip with a candle before you do step 3. Explanation: One property of water is surface tension. Water molecules are attracted to each other, but the molecules on the surface have no molecules above them to be attracted to. Because they are attracted to molecules all around and below them, a tension is formed. This tension forms a thin skin on top of the water. This skin is strong enough to support the paper clip. But if the clip is lowered at an angle, or hits the water with too much force, the surface tension is broken. Another demonstration of surface tension would be to observe water striders or other water insects that "walk on water".