Explaining the science in the sky

CMU professor breaks down the chemistry of fireworks

​ ​​​​With the Fourth of July holiday around the corner, explosions of fireworks in the night sky are the official sights and sounds of summer. It's one of the best times of the year for Gabriel Caruntu, a professor of chemistry and biochemistry at Central Michigan University and expert in the science behind the colorful bursts.

 "The chemistry of fireworks is complex and I think that makes it interesting for everyone," he said.

 

When teaching students about the inner working of fireworks, Caruntu's favorite demonstration is one he calls the "chemical volcano." Similar to fireworks, this reaction starts with thermal energy – in the form of a flame – added to an orange chemical. When the flame reaches the solid, it initiates a reaction where the orange solid "erupts" and changes to a fine green powder.

As the chemicals react with one another, gases are emitted. These gases cause the green powder to float above the reaction, simulating a volcanic eruption. Chemical reactions in a solid state like this experiment and those in fireworks, are unique. Typically, reactions take place in a solution.  Another unique aspect can be the release of high amounts of energy, which sometimes causes the air to expand faster than the speed of sound and produces a shock wave – called a sonic boom – giving fireworks their signature sound. 

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