Dry Ice Crystal Ball Bubble

This is by far my favorite science experiment to do with the kids.  I have done it with my kids numerous times, but I've also done it at a class Halloween party and at a home Halloween party, and in both cases, it was a huge hit.  The bubble grows and grows, and stays around for at least 30 seconds, and sometimes up to a minute before it bursts into a cloud of fog (which is cool in and of itself).  It gets so big, it ends up looking like a crystal ball, which makes it perfect for Halloween.  Everyone has their favorite part...  some like to watch the fog that builds up inside it, some like to blow on it and see it move and form into different shapes (see below),  and some like to watch the rainbow of colors that forms on top of it (the prism effect).  In any case, whatever your kids' and audience' favorite part is, I can pretty much guarantee a series of ooohs & ahhhs as they're watching this thing grow and burst.

Preparation

To find dry ice in a store near you, you can use this dry ice directory.  Dry ice should be purchased right before you plan to use it as its temperature is cooler than the freezer's, and even in there it will last just a few hours before it evaporates.  Because of its extremely cold temperature, dry ice will burn the skin.  I use a hammer to break it, and a heavy duty glove (picked up from the gardening section at our local hardware store) to pick it up.  The kids are not allowed to get near it - not even with a heavy duty glove.  Sorry, but there's a whole lot of other cool stuff they can do in this experiment.  As you can see in the photos below, my four year old pretty much did the whole experiment by herself.  But, the dry ice is MY job.

A rounded rim for the bowl you're using is absolutely necessary, and the experiment will not work without it.  I used this Pyrex 2-1/2 quart mixing bowl.  You'll have to experiment with the fabric - just keep in mind if the experiment does not, you're probably using the wrong type of fabric.  I used some leftover fabric I bought at Joann's Fabrics by the yard, and it worked like magic.  T-shirt material did not work for us, and also folding the fabric does not work - it has to be completely spread out.  You'll need a strip of fabric about 1'' wide and about 18'' long (or about 4-5 inches longer than the diameter of the bowl you're using).

The Experiment

Take your small cup, and fill it up with about 1/3 cup of warm water.  Then add 2 tbsp dish soap, and mix well.  Now soak the strip of fabric in the soapy solution (#1).  Make sure the fabric is completely submerged in the bubble solution (#2).  Fill the bowl about half full with warm water.  Using your heavy glove, transfer two pieces of dry ice into the warm water.  You should immediately see some fog produced (#3).

Dip a finger in the soap solution, and run your finger on the lip of the bowl (#4).  Be careful not to get soap in the water.  Remove the strip of fabric from the soapy solution, and run it between your thumb and forefinger to remove excess soap (#5).  Stretch your fabric between your hands, and slowly pull it  across the rim of the bowl.  Soap film should start to stretch across the bowl (#6).  It should eventually stretch across the entire bowl in which case all that's left to do is wait!

If this doesn't work for you, try a couple more times, but most likely it's not how you're doing it, but the stuff you're using to do it.  Either your ratio of water to soap is a bit off in your bubble solution.  In which case you can just play with it a bit, or just use any old bubble solution (either store-bought or homemade - both worked for me).  Like I said before, the other factor that could be contributing to the bubble not forming is the fabric.  Just try a few types of fabric, and you'll figure it out.  Mine worked on the second try...



The soap film will start to expand and fill with the dry ice fog.  You can see the bubble starting to form on #7 above.  And in #8 you can see it pretty much at its full size right before it burst.  In #9 below, you can see the rainbow of colors that formed when the light hit the bubble and bended, causing it to separate into the many colors it's made up of.  Isn't it beautiful?!  In #10 below, one of the kids blew on it, and it actually did not burst (which is what usually happens!).  Instead, it created this really cool shape my friend was actually able to take a picture of!

How Does It Work?

Dry ice is frozen carbon dioxide.  When you drop pieces of dry ice into water, a gas bubbles out of the water.  This gas is a combination of carbon dioxide gas and water vapor.  The thin layer of soap film stretched across the rim of the bowl traps the expanding cloud of gas to create a giant bubble.

Ready for More?

If your dry ice supplier is anything like our local grocery store, they'll not sell you just a few pieces of dry ice.  Of course, you can do this experiment over and over again (and I can't imagine you'll hear any objections), but another experiment that goes really well with it, is Boo Bubbles.  The Boo Bubbles experiment is based on the same concept as the Crystal Ball Bubble, but the kids actually get to hold and bounce the fog-filled bubbles, which if you're a kid (or a kid at heart) adds a whole new dimension to the whole thing!  So, head over to my Boo Bubble Experiment post if I've inspired your curiosity, and head over to my Halloween Science Party post for more Halloween science ideas.

I hope you had fun with this!  Please share your experiences!  

See you soon,