If you've ever just wanted to muck about with some dry ice, here are some YouTube videos with fun experiments to try — starting with making your own.
Dry ice is a curious substance. It's not water at all, but frozen carbon dioxide, which needs a temperature below -78.5 °C in order to freeze. When the temperature starts to rise, the carbon dioxide does something curious: it skips the liquid form most substances undergo and sublimates — that is, transforms directly into a gas.
While this is all very interesting scientifically, and makes dry ice great for keeping food cool during transportation, it also has the potential to be a heck of a lot of fun.
First of all you have to get your hands on some. Not literally, because it can burn your skin off. (As an interesting aside, this is why you should never put ice on a burn. Run it under a cold tap for at least 20 minutes, then, if it is open and weepy, cover it with something clean and non-adhesive. Hospitals prefer cling film.)
If you have a spare CO2 fire extinguisher just kicking about, you could try Dr Gareth Francis' method for making it yourself. We suspect, however, it would be a lot easier to just buy dry ice than somehow locate a fire extinguisher that no one wants.
Anyway, however you get it, pretend you now have some dry ice. What are you going to do? Firstly, go get some safety equipment: thick insulated gloves or tongs for handling the ice, and some safety glasses. Make sure you perform all experiments in a well ventilated area and never store it in an airtight container, unless you want a CO2 explosion. You can read some more safety tips here.
Okay. Now gather yourself up a plastic bowl and cup, some dish soap, some cloth strips and some warm water. You're going to make yourself an spooky bubble filled with CO2, courtesy of Steve Spangler. He also shows how to make some smaller bubbles here.
For something a little more grown-up, Dr Anne Helmenstine shows you what happens when you put dry ice in the microwave. It won't harm your microwave, so you can go ahead and try it yourself, then refer back to Dr Helmenstine's videos to find out why the dry ice did what it did.
For something a little bigger, who has a swimming pool? (The good bit starts at 1.30.)
Though not surprising, this actually looks really cool. So cool, in fact, that we think it's time to up the gas ante by mixing dry ice with liquid nitrogen.
Oh, heck with it. Let's just go with these explosions.
Maybe don't try this one at home.