Some ghosts like playing with bubbles just as much as kids do! In this experiment, watch as your normal soap bubbles seem to float midair!

What you’ll need:

-Empty fish tank or other clear tub container

-Dry ice, which can be found at Central Market or the HEB on Congress and Oltorf

-Tongs, a thick hand towel, or oven mitts to pick up the dry ice (Warning!: Dry ice is so cold it will burn your bare skin, so make sure you don’t use your hands to pick it up!)

-Bubble mix and bubble wand

What to do:

 Fill your container an inch deep with warm or hot water. Use your tongs, thick hand towel, or oven mitts to drop a few pieces of dry ice in the container. The dry ice will start to sizzle and smoke as it transforms from a carbon dioxide solid into a carbion dioxide gas.

As you patiently wait for the fog to die down, you can blow some experimental bubbles and watch them bounce on top of the fog!

When the fog dies down and the container looks mostly empty, blow some bubbles in the container. Watch as the bubbles mysteriously float midair instead of immediately sinking to the bottom…as if a ghost was holding it up! Invent a story about what kind ghost haunts your fish tank!

So why does this happen?

Even as the smoke dies down, there’s still an invisble layer of carbon dioxide gas. Carbon dioxide is heavier and more dense than air, which means its particles are more condensed (tightly packed together) compared to air’s. The bubbles full of air float on top of the gas because it has a lower density than the carbon dioxide.

Let’s use water as another example. Just like the bubbles on top of the carbon dioxide gas, a beach ball full of air floats on water because the stuff that makes up air is more spread out than the stuff that makes up water—giving it a lower density than water.  An anchor, however, sinks because the stuff that makes up an anchor is more packed together than the stuff that makes up water, giving it a higher density than water.

This is the last experiment in a three-part series featuring dry ice. You can find out more information about dry ice and also check out the first two experiments here and here!