UPSIDE-DOWN ‘U’ (Amazing Science Games and Experiments)

Materials Required:

1. 2 jars
2. Water
3. Box (2-feet high)
4. Flexible tube (rubber or plastic)

Procedure:

1. Fill up one jar completely with water and set it on top of the box. Place the empty jar on the ground beneath the full jar.
2. Cut a piece of rubber or plastic tube long enough to reach between the two jars. Hold both ends of the tube
   together under the faucet until the
   tube gets filled entirely with water.
3. With your fingers, pinch both ends of
   the tube closed. Place one end in
   the jar of water, pushing it beneath
   the water level. Release your hold,
   but make sure the tube rests on the bottom of the jar.
4. Place the other end of the tube
   into the empty jar and release it. The
   water will flow from the full jar to the empty jar until all the water is completely transferred.

This is what happens:

You have just created a device called a siphon. Notice that the shape of your siphon is really an upside-down ‘U’ with one long side. As the water falls down this long side, a vacuum is formed at the bend in the ‘U’. Air pressure against the water in the top jar pushes water into the short side of the tube where it climbs up until it reaches the bend, and then falls. The process occurs continuously until the flow of water is interrupted, such as when the jar runs dry, or when air gets into the tube, disturbing the vacuum.