So, it's 4th of July. You and all your pals are standing on the roof of your building watching the dazzling display from downtown. Ever wonder what puts the crack in those crackerjacks? If so, here's how to understand how they work.
Every firework is a different chemical compound or similar compounds with slightly different compositions. Those falling stars are different from the bright, cackling sparklers. The greens, the blues, the reds, the purples are all made up of different chemical compositions. A little understanding of basic chemistry goes a long way!
There are three basic types of energy produced by fireworks: sound, light, and heat. These are produced by several different chemical reactions.
The huge booms you hear on the ground are due to the quick release of energy into the air, which causes the air to expand more quickly than the speed of sound, causing a sonic boom! The whistling you hear in some fireworks is due to air expanding out of tiny holes as the interior of the firework burns - it's a lot like whistlin' Dixie.
The colors and general "firepower" of fireworks come from the chemical reactions of different types of metal salts, which are added together in specific combinations for the desired reaction. The explosions and colors of fireworks are due to heating these different elements in conjunction with black powder and other chemical agents.
The colors themselves are the fun part. Each element added to a firework has a unique chemical composition which, when heated, gives off different colors of the spectrum.
For example: to get a red blast, you would add together strontium and lithium salts along with strontium carbonate. These chemical agents are then packed into little lumps called "stars" which are what give the firework its pattern and appearance. The stars are further packed into cardboard and then placed inside the firework shell, where they await a time-delay fuse. After the initial ignition of the firework, the time-delay gives this little chemical combustion factory a chance to get up to the sky before it shows all its glory.
Of course, there is much more to understand and learn about the chemical reactions in fireworks. Hopefully, next 4th of July we can all look up at the sky at have a little better understanding of what we're seeing.