Materials Required:
l Pail
l Water
l Lightweight plastic box (like the kind that berries are sold in) with holes in the bottom
Procedure:
- Fill a pail, or any deep container, with water.
- Make sure the berry box is dry, then gently set it on top of the water surface. Even though the box has large holes in the bottom and sides, it will float easily.
- Look closely at each of the bottom holes. A puffy square of water sticks up inside the box.
- Now give the box a little push downward. It will sink to the bottom of the pail.
This Is What Happens:
Surface tension of water has an elastic quality that supports the weight of the berry box. You could see this stretchiness as the water protruded through the holes into the bottom of the box. But when you push the box downward, the force of that push is great enough to break the surface tension of the water, sending the water streaming through the open holes. Finally, when the box is surrounded entirely by water, it sinks.
