Rising Water Tension (Funky Physics Experiments)

You will need:

1. A clear glass
2. Water
3. Some coins
4. Saucer or plate

Challenge your friends into trying to raise the water level in a glass higher than the glass itself. When they don’t know how to do so, pull this neat little trick.

INSTRUCTIONS

1. This experiment can get messy, so place a large plate or saucer on the table and then place the glass on it.
2. Slowly fill the glass with water all the way up to the brim.
3. Now very gently, drop coins into the glass of water one at a time, with the rim (and not the flat surface of the coin) going in first.
4. Even though the glass is filled with water, you might be able to drop one or two coins, or even more before the water spills out.

RESULT

The water level in spite of having risen above the glass level does not spill over. This is because of surface tension, which holds the water molecules together, thus preventing the water from spilling over. However, surface tension can keep water molecules together only up to a limit. When the bond between the molecules gets too taut, the surface tension breaks and gravity pulls the water over the edge into the saucer.