Dry ice is fun stuff to play with, but be careful. Wear gloves, and don’t be a dumbass, because there is the potential for substantial injury. You’ve been warned, now there are some real cool things you can do too. I probably don’t know the half of it.
You can make a good liquid nitrogen substitute by mixing the ice with water, and dipping things in to freeze them. Watch your fingers! But the coolest aspect of the dry ice and water reaction is called sublimation, where the frozen carbon dioxide changes directly from solid to gas.
One of my favorite (I might not have been the brightest) games to play when I was younger was to fill a plastic bottle with a quarter sized piece of dry ice and water, lightly screw the cap on, and wait for it to shoot off. It wouldn’t go all that straight, but there was a general aim involved, and I could hit a target maybe twenty feet away.
My new quest is to build a self pressurizing rocket out of a 2 liter bottle. I made a quick test bottle yesterday, screwed the cap on lightly and rigged the nozzle in a downward direction set for launch and then took my distance from the bottle. I started to get worried as the plastic cracked and filled, the pressure was getting past the point that it would normally blow the cap off. I didn’t dare walk over to it – and all the sudden it blew open with quite a crack. Now thank god this wasn’t a two liter bottle, it was only 16 ounces. But it sure did make a loud bang.
So now I’m starting to think how I could make the best kind of launcher for a rocket. Ideally it would monitor the pressure in the launch chamber, and trip a release when it arrived at the right level, with no human factor involved. There is a neat design to launch air and water pressure rockets this way – the clark cable launcher. It looks like a real neat one, but I can’t find any of the right sized pipes in my garage. I’m going to do a test today with an improvised rubber stopper in the bottle mouth – an old bicycle inner-tube wrapped around itself to fit. I’ll see how far that gets me.