Dry Ice Crystal Ball Bubble
Widely renowned for being the key to smoking, bubbling, fog-filled science, dry ice is also an important ingredient for seeing into the future. You don't believe us? You clearly haven't experimented with the Dry Ice Crystal Ball Bubble! In this experiment, you'll create a crystal ball bubble just by using some household items and a bit of dry ice.
- Dry ice
- Large bowl with rounded rim
- Dish soap
- Heavy glove or tongs
- Long, narrow piece of cloth
- Small plastic cup
- Warm water
- Mix 2 tablespoons (30 mL) of liquid dish soap with 1 tablespoon (15 mL) of water in a plastic cup.
- Cut a strip of cloth that is about 1" (25 mm) wide and 18" (46 cm) long.
- Soak the strip of cloth in the soapy solution you made in step two. Make sure the entire cloth is submerged in the solution.
- Find a bowl or bucket that has a smooth rim and is smaller than 12" (304 mm) in diameter. You don't need a clear bowl or bucket, but trust us, you'll want one.
- Fill the bowl half full with warm water.
- Using heavy gloves or tongs, transfer two or three pieces of dry ice into the warm water. You don't want too little or too much fog to be produced.
- Dip one or two fingers in the soap solution and run your fingers on the lip of the bowl. (Be careful not to get soap in the water, otherwise you'll end up doing another experiment.)
- Remove the strip of cloth from the soapy solution and run the cloth between your thumb and forefinger to remove excess soap.
Stretch the cloth between your hands and slowly pull the soapy cloth across the rim of the bowl. The goal is to create a soap film that stretches across the entire bowl.
HINT: Getting the soap film to stretch across the rim of the bowl can take a little practice until you get the technique mastered. If all else fails, try cutting a new strip of cloth from a different type of fabric (try an old t-shirt) or change the soap solution by adding more water or more soap.
- Once you've made the soap film, it will start to expand and fill with the dry ice fog. Once it bulges out, it looks just like a crystal ball.
- When the giant bubble bursts, the cloud of "smoke" falls to the floor, followed by an outburst of ooohs & ahhhs!
Try placing a waterproof flashlight in the bowl along with the dry ice so that the light shines up through the fog. Draw the cloth across the rim to create the soap film and, if you're inside, turn off the lights. The crystal ball bubble will emit an eerie glow and you'll be able to see the fog churning inside the transparent bubble walls.
How Does It Work?
When you drop a piece of dry ice in a bowl of water, the gas that you see is a combination of carbon dioxide and water vapor. So, the gas that you see is actually a cloud of tiny water droplets. The thin layer of soap film stretched across the rim of the bowl traps the expanding cloud to create a giant bubble. When the water gets colder than 50ºF, the dry ice stops making fog, but continues to sublimate and bubble. Just replace the cold water with warm water and you're back in business.
Bob Becker presented this activity during a lecture at the National Hands- on Science Institute (www.nhosi.com) in Denver in 1997. Bob is a chemistry teacher from Kirkwood, Missouri, who constantly searches for new ways to turn students on to the wonders of science.