By: Tom Wickersham

Explorit Looks at the Chemistry of Fireworks

Whether you celebrate tomorrow's holiday by raising a flag, having a bar-b-que, or traveling out of town, chances are that at the end of the day you'll find yourself on a blanket surrounded by lots of other people on blankets all looking up at the sky.

Every year, millions of Americans celebrate their country's birthday by watching a fireworks display. Lots of "ooohs" and "ahhhs" and booms can be heard as the sky is filled with a dazzling color show of reds, blues, yellows and greens. These sounds and colors are the result of chemical combustion.

Pyrotechnics, or the art of manufacturing or setting off fireworks, began hundreds of years ago in China with war rockets and explosives. Arabia also used fire works early on. Later, fireworks were introduced in Europe and today fireworks are enjoyed worldwide.

Fireworks usually include two explosions. The first propels the rocket into the air. The second produces light and/or sound. The colors we see are due to the characteristic energies of the light given off by specific compounds. Copper salts like copper acetoarsenite produce a blue light. If you see red, you're seeing a lithium or strontium reaction. Barium compounds such as barium carbonate or barium chloride produce greens and sodium compounds produce yellow.

How about the Earth-shaking BOOMS? With the right oxidizer and fuel, the fireworks will produce sound. Salts, such as sodium salicylate, used as a fuel, burn one layer at a time emitting gas in "spurts." These rapid emissions cause vibrations which produce sound.

So if you're in Davis tomorrow, check out the fireworks display at the Community Park. See if you can "analyze" the chemistry of the reactions. Identify the number of explosions in each firework. See what colors are used more frequently. What about the colors you see infrequently? Think about why some colors might be used more than others.

One final note: in honor of Independence Day, Explorit Science Center will be closed July 4, but will reopen on Sunday, July 5, from 1:00 to 4:30 pm.

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Do you, perhaps, remember the "experiments" with toys you conducted as a kid? If you had cars and race tracks, for example, you might have tested all your cars to see which one jumped the farthest. Here's your chance to try those experiments again.

After July 4, visit The Way the Ball Bounces: The Science of Toys and Games at Explorit. Try experiments to answer the following questions: which ball bounces highest, a tennis ball, superball(TM), or a racquetball? What if they are bouncing on wood? Carpet?

Try the parachute launcher. Which material makes the best parachute? How does a parachute's shape affect its flight? And finally, test those race cars. What does it take to complete a loop? Can you get the car to complete two loops?

Try these and dozens of other activities and experiments at Explorit. Here's your chance to bring in the kids (or be a kid again) and play with all sorts of toys. You just might learn a thing or two about science.

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Explorit Science Center is located at 3141 5th Street in East Davis. The current exhibition is The Way the Ball Bounces: The Science of Toys and Games. Public hours are Saturday from 11:00 a.m. to 4:30 p.m., Sunday from 1:00 to 4:30 p.m., and Tuesday through Friday from 2:00 to 4:30 p.m. Regular admission is $3; members, teachers (with school ID) and children under 4 are free.