posted by Beret
Ages: 6 and up. Actually, any age is probably ok, as long as your kid can wear goggles and gloves and responds appropriately to “No!” and “Don’t touch that!”
Included in this post:
- What is Dry Ice?
- Getting Started
- Balloon Blow-Up
- Film Canister Rockets
- Bubbles and Fog
- Freeze-drying Plants
- Where to get dry ice and how to store it
Due to a healthy dose of good fortune, each of my kids has befriended a small person whose mom is a scientist. It’s hard to explain how groovy that is.
Imagine that you invite a couple of your kids’ friends over to do a science project, and one of the moms brings THE MOST AMAZING MICROSCOPE. Not the kind you buy at the toy store; not the kind you use for middle school science classes. The kind you use in the lab. I couldn’t wait to get my turn. Once the kids wandered off to do other things, I started rummaging through the refrigerator for molding items to examine.
I never know what to expect on playdates at their houses, either. I’ve overheard things like, “Do you want to pet our dead cat?” and “Want to make sunprints?” in addition to the usual, “Let’s try to tie up my dad again like last time.”
One Saturday in May, we were invited over for some experimentation in the garage. “I’ll get some dry ice,” science mom added.
What is dry ice? Dry ice is the solid form of carbon dioxide, and it is about -110° Fahrenheit (-78°C). That means it’s darn cold. Very brief, hot potato-style contact with the skin is usually harmless, but at that temperature, it doesn’t take long to freeze and damage your your tissues permanently.Another handy thing to know: at normal air pressure, dry ice does not melt. It sublimates, or turns directly from a solid to a gas. That is why it ‘smokes’ and looks so awesome.
Getting started: Dry ice is not just cold; it’s also cool. Be sure to give kids plenty of time to ooh and ahh, and get to know the stuff. Just watching it and chopping it is pretty entertaining. If you press a quarter against the ice, for example, it will make a screaming sound. Lucky for me, my kids figured out that pressing it with the hammer in a certain way made farting noises. They probably could have done that all day, but I had a few other activities in mind. Blowing things up, for example.
Like balloons, not people, of course.
Balloon Blow-up.Using tweezers or tongs, put a small piece of dry ice into a balloon. Crush it a little with gloved hands, and tie a knot in the balloon. As the dry ice sublimates, the balloon will expand with CO₂.
Film Canister RocketsYou can ask for empty film canisters at a local film developing shop or art school. Using tweezers, put a small chunk of dry ice inside, secure the cap, and stand back. Voilá, a film canister rocket. As sublimation occurs, the canisters will fly up and pop open. Remind kids: don’t point these at anyone!
Bubbles and Fog
Put warm water in a glass or beaker (or bucket, even), and add a piece of dry ice. The warm water speeds the sublimation process, so fog forms quickly. (See photo at the top of the post). If you like, try adding food coloring to the water after a while, to see what happens…or doesn’t.
To warm water, add dishwashing liquid and a piece of dry ice.
Bubbles will start climbing up the sides. Mesmerizing to watch. I love when large bubbles burst and release a cloud of CO₂.
We put several exceedingly generous squirts of soap into our 1000ml measuring cup, which turned out to be waaaaay more than necessary. We also put in a couple of fairly large chunks of dry ice, and that potion bubbled for a couple of hours. We started adding food coloring, too, to see what might happen. Wandering back now and then to check on it, we noticed that a little blue cave of ice formed in the solution.
Freeze drying plants.
If you add a chunk of dry ice to a container of denatured or rubbing alcohol, it becomes a kind of “super freeze” solution. Dip in a daisy until it looks frozen, then try dropping it on the ground. If it’s fully frozen, it will shatter. Try other plants, rubber bands, whatever intrigues you.
Science mom is braver than I am. She stood back and let the kids do their own experiments all afternoon. The were completely focused for a couple of hours, and I was pleasantly surprised that nothing irreversibly terrible happened to anyone or anything after dry ice, bubble liquid, rubbing alcohol, Diet Coke, Mentos, and more were added to buckets and observed. Did I mention the gloves and goggles, though?
I got several of the activities listed above from www.usafa.edu.
Lawrence Hall of Science puts out great resources for science projects at home and at school. Here is book called Dry Ice Investigations which contains 11 science investigations for grades 6-8, plus all kinds of information for teachers.
Where to get dry ice and how to store it:
In San Francisco, it’s a no-brainer: head to the San Francisco Ice Company in Bayview. It’s a dollar a pound, with a minimum purchase of ten pounds, and open seven days a week. For those of you who live elsewhere, party supply stores and grocery stores often have it. Just Google “dry ice” + your city. Since many people use it to make ice cream, it’s not too tough to find.
Sublimation takes place quickly, so purchase the dry ice as close as possible to the time you will use it. When I asked how long it would last in the freezer, I was told not to put it in there. The air blowing in the freezer will cause the dry ice to sublimate in a number of hours. Instead, I was advised to keep it in a cooler, where it would last for about two days. Evidently, a styrofoam ice chest is the best place for storage–my apologies, Mother Earth–because it is insulated, but not air tight. There is some danger that it will cause an explosion if kept in an airtight container. Also, do not leave dry ice in a car with the windows rolled up. I doubt it would blow up the car, but it isn’t healthy for the people and pets inside.
On the other hand, if your refrigerator breaks, tossing in a chunk of dry ice is a great temporary fix.
One science mom used dry ice on a canoe trip, and managed to have cold beers on the seventh day of 100° weather. Don’t put it in the cooler with the beer, however. That results in disaster. Use it to keep a cooler of ice frozen instead.
For more information on dry ice safety, click here.
For other uses for dry ice–including making rootbeer and eradicating gophers!–click here.
***Special thanks to Katherine Nielsen and Petra Dekens for being so awesome, and for having great kids the same ages as mine.