Cartesian Diver

For younger kids

Time: 10-15 mins

Do you want to amaze your friends with seemingly “magical” pen cap? You should build the cartesian diver!

You will create a little water bob, called a Cartesian Diver, that can can sink and float in a bottle of water on command!

Materials:

• 1 pen cap

• 1 clear, 1-liter plastic bottle

• Some modelling clay (like Play Doh)

• A sink

Steps:

1. First, fill the 1-liter bottle with water, all the way to the top. Make sure to set the bottle in the sink, in case it falls over on accident!

2. Next, place a little bit of clay on the tail of the pen cap. Make sure the clay stays on tight!

3. Place the pen cap into the bottle of water, tailside first. Some of the water should fall out of the bottle and into the sink.

4. The cap should just barely be floating in the bottle. If the cap floats too easily, add a little more clay. If the cap sinks, then you need to take a little clay off.

5. Tightly close the bottle cap. You could even put tape over the bottle cap to make sure it doesn’t come off if you want. Finally, your cartesian diver is ready!

To make the diver work, squeeze the bottle in your hands. Watch as the cap sinks! To make the cap float back up to the top, just let go of the bottle. It’s like magic!