Inside the Witch’s Cauldron: The Science of Dry Ice

It’s the season for all things spooky and scary! From witches and warlocks to jack o'lanterns and sweet treats, there’s so much wonder to behold during the Halloween season.

Looking for a fun activity to get in the festive spirit? With a few simple ingredients, you can make your very own witch’s cauldron for decoration. All you’ll need is some dry ice—and water, of course!

How can ice be dry?

At Aqua, we’re always fascinated (but never surprised) by water’s versatility and the ways that it can teach us new lessons about the world around us. Though there’s nothing spooky about water, it’s a key ingredient in a DIY witch’s cauldron that’s sure to wow trick or treaters.

 The other key ingredient is dry ice, which is exactly what it sounds like: ice without water. That may be hard to imagine, but it’s possible because of carbon dioxide.

Believe it or not, dry ice is colder than ice made with frozen water. Essentially, dry ice is carbon dioxide (with no moisture or air) that’s frozen at -109.3°F, while regular ice freezes at 32°F. So what happens if water and dry ice meet? Let’s just say things can get spooky.

When the dry ice meets water, it immediately undergoes sublimation, which means it changes from a solid to a gas without ever becoming a liquid. The best part of it all? Water is a catalyst that helps to create this phenomenon!

How to make a DIY witch's cauldron

First and foremost, you’ll need the main ingredient: dry ice. If you aren’t sure where to buy it, call your local grocery store to see if they carry it. If not, search online for a supplier near you.

 Next, look for a cauldron at a Halloween store, or use a large cooking pot from your kitchen. Even if it doesn’t look exactly like a witch’s cauldron, your bubbling potions will still look festive.

Fill the cauldron about halfway with hot water and a dash of dish soap, which will help to give you bubbles. Then, using tongs, place small chunks of dry ice into your soapy water mixture and watch as the kettle starts to gurgle and bubble. Remember to handle the dry ice with care—due to its negative temperature, touching it with bare hands can give you frostbite.

To keep the potion going, add more hot water when needed. Your neighbors and friends will surely be wowed by your crafty decor.

Whether you’re trying this craft out in your kitchen with the kids, in the classroom with students, or at a party with friends, we hope you enjoy watching this fascinating scientific reaction unfold.

Happy Halloween!

Share This Post: