by STEM Scouts
This post is an edited version of an experiment write-up originally appearing on Steve Spangler Science.
Watch our experiment on the STEM Scouts Facebook page.
- 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.
- 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.
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 bubble will emit a 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.