n this easy experiment, you will observe the movement of paper circles that seem to have a mind of their own.
Things Required:
Piece of notebook paper
Paper hole punch
Small glass with no more than a 2-inch diameter (candle holder or an egg holder will work) eye-dropper
Toothpick
Directions:
Use the hole punch to cut three or four circles from the paper. Fill the glass about three-quarters full with water. When the water is calm, place paper circle on the surface in the centre.
Results: After a few seconds the paper moves to the side. Add two more paper circles and using the toothpick, move the circles to the centre of the water.
Results: The paper continues to move towards the edge.
Remove the paper and fill the glass so that it may overflow may with water. Use the eye-dropper to add the extra drops needed to make the water bulge above the sides of the glass. When the water is calm, place the paper circles in the centre. Use the toothpick to move the circles towards the edge carefully; then release them. Be sure that you do not force the water over the edge of the glass. Repeat.
This Is What Happens:
The paper continues to move towards the centre of the water.
Science Behind It:
Surface water molecules pull on one another, but they are more attracted to the molecules in the glass. This attraction causes the water to be pulled towards the glass. The water on the paper that is placed in the partially filled glass is pulled towards the edge, carrying the lightweight paper circle with it. The glass that is overfilled with water does not have the exposed glass sides for the water to be attracted to. The result is that the water molecules pull on one another with the force directed towards the centre of the bulge of the water. The wet paper is pulled towards the centre because the water on it is pulled in this direction.
