Dry ice activities are a fun way to demonstrate scientific principles during this spooky season! People use the substance during Halloween to create creepy fog in cauldrons and other decorations, which means you may be able to pick up some at the grocery store.
Dry ice is solid carbon dioxide, or CO2. We usually think of carbon dioxide as the gas that we expel from our lungs when we breath out. It is also the gas that trees and other plants need to absorb to survive. They then expel oxygen, which we breath in. It’s one big cycle!
To understand dry ice, it helps to think about water, or H2O. When it is solid at colder temperatures, we call it ice. As temperatures warm up and the H2O molecules heat up and start to move around, it turns into a liquid. Turn up the temperature even more and H2O turns into water vapor or steam, which is a gas. These are the different states of matter.
CO2 as dry ice transforms from its solid state directly into its gas form. It completely skips the liquid state. This is called sublimation. And it lets us do some very cool things!
And when I say cool, I mean cool. It freezes solid at 109 degrees below zero Fahrenheit. That’s about 100 times colder than the ice in your freezer!
Before we get started with our cool activities, let’s talk safety. Because it is so cold, dry ice can give us a cold burn or frostbite very easily. Always have a responsible adult around when working with dry ice. It might be best for the adult to be the only one handling the dry ice.
You need to use heavy-duty gloves when handling dry ice. Lay a towel down over the big block of ice and then use a hammer to break it up into smaller pieces. Use tongs (plastic is best!) to transport pieces. Treat any minor burn like you would frostbite or a burn from heat. Seek medical attention in severe cases.
Making fog
In a tall glass, add dry ice to the bottom. Then add hot water. (The water should be steaming but not boiling.)
What happens? You created fog (a gas) that floats over and down the glass thanks to the sublimation. Do you notice that the fog sinks to the bottom of the table? That is because it is denser than air. If you put your hand in the CO2 fog, you will notice it still feels very cool!
Making bubbles
Now add dish soap to the glass. We love Dawn because it creates strong bubbles.
What happens? That’s right, bubbles full of CO2 foam out of the glass. They are fun to play with! Do they pop? Yes. If you grab at the ghostly bubbles with a glove, do they pop? No! It’s because we have oils on our hands that are the natural enemy of bubbles. With the glove to protect them, we can play with the foam for a while first. Such fun!
Make a bubble dispenser
With a few extra supplies, you can create massive ghostly bubbles. You need a container with a lid (big enough to hold between 2 liters and 1 gallon), a couple feet of plastic tubing, a small potion-sized plastic cup, duct tape and scissors. Cut one hole in the side of the large container and another hole in the bottom of the cup that are large enough to fit the plastic tubing. Connect the large container and the cup with the plastic tubing. Seal with tape so no air can escape. You’ve created a bubble dispenser!
Next get a small bowl and fill it with water. Add enough soap (Dawn again!) so that the water turns light blue.
Put dry ice in the bubble dispenser. Add hot water, then screw on the bubble dispenser’s lid. Take the bubble dispenser’s cup and dunk it in the bowl of soapy water. Once you’ve created a soap seal over the cup, pull it up and watch as large ghostly “boo” bubbles form. The carbon dioxide is trapped inside!
Because CO2 is denser than air, the bubbles will fall down. They will pop once they hit a hard surface or your hand if there is any dirt or oil on it. But add a towel on the table or put a glove on your hand and it will stick around. Can you hold the ghostly bubble in your hand?
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