1) Fill the pop bottle all the water. Insert the eye
dropper, making sure the dropper is about half-full of water. Screw the cap
on the bottle tightly.2) By squeezing the
sides of the bottle, you can make the eyedropper plunge to the bottom, float
back to the top, or even hover halfway!
3) You can make this look like a magic trick by
holding the bottle in one hand and a pen or other object in the other hand.
Tell your audience that you can make the dropper move by magic. Then point
the pen at the dropper while at the same time squeezing the bottle. As the
dropper descends through the bottle, move the pen accordingly. If you do
this carefully, you can make it look like the pen is moving the dropper, not
you!
Explanation: Liquids, such as
water, are incompressible - meaning their volume is constant. Gases, like
air, are compressible. So when you squeeze the closed bottle, the water
can't be squished any smaller - but the air inside the eyedropper can. This
makes more water flow into the bottom of the dropper, making it heavier, and
sending it to the bottom of the bottle. As soon as you release the pressure
on the bottle, the dropper floats back to the top!
