SODA BOTTLE FOUNTAIN

Have you ever stopped to watch a fountain in the park or mall?  Sure you have, everyone does.  Ever wonder how they work?  Well, in this experiment, we'll show you the principle that fountains use.

You Will Need:

• 1 plastic soda bottle of any size (large ones work best)

• Water

• Room to work, where it won't matter if the water gets on the floor (outside might be best)

• Sharp pointed utility or crafts knife

• Paper towel (or regular towel)

• Tape

Doing the Experiment

This is an easy experiment that only takes a few minutes.

1. Remove the label from the soda bottle.

2. Fill the soda bottle all the way full with water.  Squeeze the bottle.  What happens to the water?

3. Fill the bottle all the way full (no room for air) again, and screw the cap on tight.

4. Try and squeeze the bottle.  If the bottle is all the way full, you shouldn't be able to squeeze it at all.

5. Now, poke a small hole in the cap of the soda bottle with the utility or crafts knife.  To get a good round hole, it is best to turn the knife while pushing down, somewhat like a drill works.

6. Try squeezing the bottle again.  You should have a fountain coming out of  the top.

7. Try squeezing the bottle different ways, soft hard, at the top, at the bottom.  Does the fountain change?

8. Take the cap off of your soda bottle, dry it off, and cover the hole with tape.

9. Fill the bottle all the way full again with water, and screw the capon tight.

10. Using the utility or crafts knife, make a vertical row of three or four holes in the side of the bottle.  Space them out so that one is about 1/4 way down from the top, one is near the bottom, and the others are right between them.

11. Remove the cap and watch the water pour out of the holes.  Is there anything different in the way the water comes out of the different holes?

EXPLAINING HOW IT WORKS

When the bottle was full of water, and you tried to squeeze it, it wouldn't squeeze because water, like other liquids, won't compress.  That's because the molecules are close enough to each other that there's no room for them to get closer.

As you squeeze the bottle, the incompressible liquid looks for a way of escape.  Finding the hole, part of it starts to come out.  Because of the pressure, instead of just leaking out, the water comes out in a stream.  The greater the pressure, the faster the stream comes out.  This allows the water to leap higher into the air before gravity causes it to fall back to the earth.

The other thing that effects the height of your fountain is the size of the hole or orifice.  Even with the same amount of pressure, a smaller hole will cause the water to go higher.  When you squeezed the bottle with the hole in the cap, the water went higher than with the cap off.  That's because the pressure is acting on a smaller area, effectively increasing the apparent pressure.  The same amount of squeezing over a smaller area produces a greater pressure.

When you poked the holes in the side of the bottle, the water coming out of the bottom hole went farther than the water coming out of the top hole.  That's because of pressure too.  The water above the hole pushes down on the water trying to get through the hole, creating pressure.  The lower the hole is in the bottle, the more water weight there is above it, creating more pressure.

By the way, a soda bottle fountain makes a great squirt gun too!