Weekend Diversion: The Physics of Fireworks!

"Celebrate the independence of your nation by blowing up a small part of it." -The Simpsons

For those of you who aren't from the U.S. or U.K., this coming Monday is the day that my nation celebrates the birth of it's independence. This date, of course, as Aimee Mann will sing to you, is the
4th Of July.
And the most common way to celebrate our Independence Day? Fireworks.

How do they work? That sounds like a question for science! (Inspired by Janet Stemwedel's article from 2007, as well as a recent article over at Scientific American.)

You start with three simple ingredients: sulfur, charcoal, and a source of potassium nitrate. Charcoal, in this case, is not the briquettes you use on your grill, which often contain no actual charcoal, but is the carbon residue left behind by organic matter (like wood) once it has been charred (or pyrolyzed), and all the water removed. Potassium nitrate is found in sources like bird droppings or bat guano. Take a mortar and pestle, mix them together, and what you'll get is a fine, black powder.
Gunpowder, in fact. All you need now is some oxygen -- readily found in our atmosphere -- ...