Everyday Chemistry: Fireworks

 
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Have you ever head the result of the equation above? If you've ever attended a Fourth of July celebration, you're probably familiar with this equation even if you don't recognize it. Black powder, also known as gunpowder, is a key chemical explosive used to liven up the night sky with colorful fireworks.

For a long time, gunpowder existed as the only known explosive. It's believed to have been first used way back in 1200AD in China. Although it eventually found use in military applications, the fireworks industry is one of the last to actively use traditional gunpowder. Three chemicals play an important roll in giving gunpowder it's combustive properties: potassium nitrate (75%), charcoal (15%) and sulfur (10%). The latter two are well known components of organic compounds.

As for the mechanics of gunpowder's explosive effect, potassium nitrate decomposes at a high temperature which provides oxygen for the reaction to take place. Charcoal, or carbon, acts as the main fuel. Sulfur can also play a part as a fuel source, but is mainly included to provide more energy and lower the ignition temperature of the charcoal. This is due to sulfur going through reactions that produce heat, also known as exothermic reactions. The reaction that produces the explosion is actually a complex chain of reactions which result in a mixture of solid and gaseous products, and a small amount of water. To get the ideal explosive property, the three chemicals must be thorough mixed, moistened, and ground to produce the proper reactive mixture.

Gunpowder is necessary to propel the firework into the air. The fuse and burning element itself can also use gunpowder. When you see the sparkling trails that follow the firework into the sky, you're seeing the charcoal burning off. The main event that gives way to a multitude of dazzling colors (and another series of chemical reactions) is the result of the ignition of gunpowder in the bursting charge.

When you're out tonight watching that triumphant grand finale, remember it's all thanks to chemistry!

 

 
Will Schneller