SUBZERO SCIENCE— Cool Science with Dry Ice
Amazing and easy dry ice experiments to explore the states of matter
Halloween is the perfect time for smoking, bubbling, eye-catching potions. But you don’t have to wait for Halloween to have fun and learn about the states of matter using dry ice. Now that you’ve read the safety rules, try these awesome dry ice experiments and prepare to be amazed!
- Dry ice
- Heavy duty gloves or tongs
- Liquid dish soap (Dawn works well)
- Drinking glass
- Plastic cylinder (optional)
- Food coloring
- Glowing light sticks (optional)
- Small fish aquarium
- Bubble wand and bubble solution
Here’s a quick experiment to help friends better understand why it’s called dry ice. Use tongs to place a regular ice cube on one plate and a similar size piece of dry ice on a second plate. Keep both plates out of the reach of children. If you ask your friends to predict what will happen to the ice during the next few hours, most will likely say that the pieces of ice will turn into puddles of water.
Allow everyone to view the plates after 1 hour and they’ll discover the difference between real ice and dry ice. There should be a puddle of water on the plate where the real ice was, but the dry ice plate will be “dry.” Where did the dry ice go? Dry ice is not made from water, it’s frozen carbon dioxide (CO2). The dry ice turned into invisible CO2 that disappeared into the air. Magic? No, it’s science.
Burping, Bubbling, Smoking Water
Use the tongs or gloves to place a piece of dry ice in a glass of warm water. Immediately, the dry ice will begin to turn into CO2 and water vapor, forming a really cool cloud. This cloud is perfectly safe for you to touch and feel as long as you are careful not to reach into the water and accidentally touch the dry ice.
To create the best effect, be sure to use warm water. Over time, the dry ice will make the water cold and the “smoking” will slow down. Replace the cold water with warm water and you’re back in business. While the term “smoke” is often used to describe what you see, it’s technically a cloud of water vapor fog.
Who would have guessed that you could have this much fun with soapy water and a chunk of dry ice? Fill a tall glass or plastic cylinder with warm water and add a squirt of liquid dish soap like Dawn or Joy. Use gloves or tongs to place a piece of dry ice into the soapy water.
Instead of the dry ice just bubbling in the water to make a cloud, the soap in the water traps the CO2 and water vapor in the form of a bubble. The bubbles climb out of the cylinder of warm, soapy water and explode with a burst of misty fog as they crawl over the edge.
Add some food coloring to the water to make the demonstration more colorful. If you want to give the bursting suds an eerie glow, drop a glowing light stick into the water along with the dry ice. The light stick will give the bursting bubbles an eerie look, perfect for any Halloween party.
Make a Bubbling Beverage
The next time you have a craving for a sparkling beverage, make your own batch using what you know about dry ice. Fill a bowl or pitcher with apple juice and use tongs to add a few large pieces of dry ice. While the mixture is bubbling and burping, the apple juice is being carbonated by the dry ice. CO2 mixes with the juice to make a “sparkling” drink. Your local hobby or craft store is sure to have a spooky-looking Halloween cauldron that would hold a large batch of apple juice and dry ice. Wait until the dry ice is completely gone before serving the apple juice. It’s a spooky carbonated drink.
You’ll notice that when you add dry ice to water, the cloud of CO2 and water does not float up into the air, but instead falls toward the ground. Why? This cloud-like mixture of CO2 and water is heavier than the surrounding air. You’ll use this little piece of science trivia to perform the amazing “Floating Bubble” trick.
A small fish aquarium works well for this activity. Fill the bottom of the aquarium with about an inch of warm water (take the fish out first!). Use gloves or tongs to add a few pieces of dry ice. Of course, the dry ice will begin to smoke as it turns into CO2 and water vapor.
Using a bubble wand and a bottle of bubble fluid, blow a few bubbles into the aquarium (it’s a little difficult so be patient). To everyone’s amazement, a few bubbles will appear to float in midair inside the aquarium. The bubble is really just floating on a cushion of invisible CO2. Of course, the spooky Halloween story is up to you . . . but I think I heard that the aquarium is the home of a ghost who has been known to play with soap bubbles!
How Does It Work
By doing the activities described in this section, you’ve learned that dry ice is frozen CO2. Under normal atmospheric conditions, CO2 is a gas. Only about 0.035% of our atmosphere is made up of CO2. Most of the air we breathe is nitrogen (79%) and about 20% is oxygen. CO2, along with a handful of other gases, make up the remaining 1% of the air we breathe.
Did you know that dry ice is often mixed with regular ice to save shipping weight and extend the cooling energy of water ice? Dry ice gives more than twice the cooling energy per pound of weight and three times the cooling energy per volume than regular water ice.
How is dry ice made? The first step in making dry ice is to compress CO2 until it liquefies, at the same time removing the excess heat. The CO2 will liquefy at a pressure of approximately 870 pounds per square inch at room temperature. Once liquid CO2 is formed, the CO2 is sent through an expansion valve and enters a pressure chamber. The pressure change causes the liquid to flash into a solid and causes the temperature to drop quickly. About 46% of the gas will freeze into “dry ice snow.” The rest of the CO2, 54%, is released into the atmosphere or is recovered to be used again. The dry ice snow is then collected in a chamber where it is compressed into block, pellet, or rice-size pieces using hydraulics.