My Cartesian Diver

Today, in science class, we made cartesian divers and raced them. The cartesian divers were made of a bottle of water with an eyedropper in it. How? When we squeezed the bottle, the eyedropper became negatively buoyant, or sunk, and when we let go, it became positively buoyant, or floated. 

All of this happened because, when the ballast, or material ( in this case water) that helps make a floating object sink, increased in the eyedropper, the diver became negatively buoyant. The ballast increased since I squeezed the bottle. When I squeezed it, the water pressure pushed more water into 

the diver, hence, increasing its mass. When the mass was increased, its density changed. If the volume is more than the mass of an object, it will float in the water. If not, it will sink, or be neutrally buoyant. At first, the volume was more, but then, the water changed the diver's mass to such an extent that it became more than the volume. If I squeeze the bottle carefully, I can make it neutrally buoyant, where the density is 1. So much science behind one little squeeze!

By squeezing fast and hard, I quickly went up and down inside the bottle, though I unfortunately didn't win. However, I learned so much from this about density! Science rocks!!!!!