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 – See Lab Safety below.
- 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
- Adult supervision
Here’s a quick activity 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!
Crystal Ball Bubble
A thin layer of soap film stretched across the rim of a bowl traps an expanding vapor cloud from dry ice to create a giant Crystal Ball Bubble. It’s a little tricky but very much worth the effort.
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, makes up the remaining 1% of the air we breathe.
NOTE: Whenever you use dry ice, always be aware of the rules for handling it safely.
- This is not a toy. It’s for demonstration purposes only.
- Use dry ice only with adult supervision.
- Dry ice must be handled using heavy gloves or tongs. It will cause severe burns if it comes in contact with bare or unprotected skin.
- Always wear safety goggles when handling dry ice. The debris and shards are extremely dangerous to your eyes. When tapping dry ice with a hammer, first cover it with a towel to keep the pieces in one place.
- Never put dry ice in your mouth.
- Never store dry ice in an airtight container. As the dry ice sublimates, gas pressure will build and the container will explode. Make sure your container is ventilated or has a loose-fitting lid.
- Do not store dry ice in your freezer. It will cause your freezer to become too cold and the freezer may shut off. On the other hand, if you lose power for an extended period, dry ice is a good way to keep things cold if you can get it.
- In the unlikely event of a dry ice burn, treat it the same as you would a heat burn. See a doctor if the skin blisters or comes off. Apply antibiotic ointment to prevent infection and bandage mild burns.
What is Dry Ice?
Dry ice is not frozen water – it’s frozen carbon dioxide (CO2). Unlike most solids, dry ice does not melt into a liquid as the temperature rises, but instead, changes directly into a gas. This process is called sublimation. The temperature of dry ice is –109.3°F (-78.5°C). Dry ice is particularly useful for keeping things cold because of its temperature. Dry ice does not last very long, however, so it’s important to purchase the dry ice you need for these science activities as close as possible to the time you need it. The best place to store dry ice is in a Styrofoam ice chest with a loose fitting lid that allows the CO2 to escape as the ice sublimates.
Some grocery stores and ice companies will sell dry ice to the public especially around Halloween. Dry ice is typically sold as flat, square slabs a few inches thick or as cylinders that are about three inches long and about a half-inch thick. Either size will work fine for these experiments. When you need to break it into smaller pieces, wear goggles and gloves and be sure to cover it so tiny pieces don’t go flying in all directions.
Remember the science when purchasing dry ice. Dry ice in a grocery bag will vanish in about a day. The experts tell us that, depending on weather conditions, dry ice will sublimate at a rate of 5 to 10 pounds (2.3 to 4.5 kg) every 24 hours even in a typical Styrofoam chest. So, again, it’s best to purchase the dry ice as close to the time you need it as possible. Last minute shopping is necessary. If you are planning to perform a number of dry ice demonstrations or have a lot of people involved, purchase 5 to 10 pounds (2.3 to 4.5 kg). A little dry ice does go a long way in these activities.
How is Dry Ice Made?
The first step in making dry ice is to compress carbon dioxide gas (CO2) until it liquefies while at the same time removing excess heat. The CO2 will liquefy at a pressure of approximately 870 pounds per square inch (4500 cmHg) at room temperature. Once liquid CO2 is formed, the CO2 is sent through an expansion valve and enters a pressure chamber. This 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, about 54%, is released into the atmosphere or recovered to be used again. The dry ice snow is collected in a chamber where it is compressed into block, pellet, or rice-sized pieces using hydraulics. It’s complicated but really cool science – really cool.
Can you make your own dry ice? Sure, anything is possible, but it’s not practical (unless you have a huge tank of compressed CO2 sitting around and lots of extra time and equipment on your hands). For around $2 US a pound, it’s hard to beat the convenience of just purchasing it at the store.
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.