Make Smoking “Boo” Bubbles from Dry Ice
In this science experiment, kids safely experiment with dry ice while exploring sublimation and phase changes.
Dry ice is frozen carbon dioxide. When it melts, unlike water, it does not become a liquid first. Instead, it immediately assumes a gas form. This is called “sublimation.” The melting dry ice is the “smoke” you see in this activity. The warm water helps speed up the sublimation process.
Because carbon dioxide gas is heavier than air; it sinks down toward the ground. So, for example, when carbon dioxide gas pours down and surrounds a flame, it suffocates the flame by displacing the oxygen that the fire needs to burn. (Fire needs three things to burn: oxygen, fuel and heat.)
"Smoking bubbles" are carbon dioxide gas surrounded by a soapy film layer. Placing your bubbles on a soapy, wet, soft surface allows the soapy film layer of the bubble to stay intact for longer. Be sure to experiment with what happens when you let the bubbles drop on a dry, hard surface!
We want to thank Steve Spangler for inspiring our design; years ago we saw a "Boo Bubble" maker for sale on his website, BeAmazingToys.com, and decided it would be fun to make our own from recycled stuff around the house!
- Dry ice is dangerous and should only be handled by an adult. If touched, it can cause severe burns. If enclosed in an air-tight container, it can also cause the container to pop open unexpectedly. Always keep children out of reach of the dry ice, always use tongs or thick leather gloves when moving the dry ice, always store it in a container with ventilation, and never attempt to chop or break it in a way that bits could fly up into someone’s face or eyes.
- Part of this experiment also involves an open flame; children should never light a match or experiment with fire unsupervised.
- Recycled plastic tub (such as a container for pretzel rods, cheese balls or craft supplies)
- 1” plastic tubing or similar (the wider the tube, the bigger and faster your bubbles will grow) - 24 inch total
- Funnel (or chop off the top of a 2 liter plastic bottle to make the same shape)
- Tape or hot glue
- Dry ice
- Warm water
- Dish soap
- Paper towel
Cut a hole in the side of the plastic tub that is just slightly smaller than your tubing, about 1/3 of the way down from the top.
Push one end of the tubing into the hole and secure with tape or hot glue as necessary.
Attach the other end of the tubing to your funnel, again using tape or hot glue as necessary. Done!
AN ADULT using tongs and/or heavy gloves should carefully place a piece of dry ice into the tub (about the size of a ½ c. measure) and add a cup of warm water. Place the lid on the tub and “smoke” should begin pouring out of your funnel! This is carbon dioxide gas.
To make a fire extinguisher: AN ADULT should light a candle. Place the smoking funnel above the flame without touching it. The carbon dioxide gas flowing from the funnel will drop down around the flame and extinguish it!
To make smoking bubbles: pour dish soap into a shallow dish to a depth of about ½ inch. The dish should be wide enough for the funnel to fit down into it. Dip a paper towel in soapy water and place on a plate. Now dip your smoking funnel down into the dish with the dish soap then gently pull up. A bubble will begin to form on the end of the funnel. Gently place the bubble on the wet paper towel; with any luck the bubble will hold its shape and sit there until you pop it and the smoke comes out!