How Chemical Reactions in Fireworks Produce Sounds and Colors


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Fireworks provide vibrant displays of color for festivities: Image by shilders

Many people enjoy fireworks displays on the fourth of July, the new year, and other festive holidays. These fireworks displays produce many loud sounds and vibrant colors, but how?

How Do Fireworks Make Noise?

When the fuse on a firecracker is lit and burns, it sets off a chemical reaction.

If the gunpowder is confined in some way, the gas is not released harmlessly. Instead, it explodes.

In a bullet, the shell confines the gunpowder so that the high pressure gas released by the chemical burning reactions propels the bullet down the barrel of the gun.

In firecrackers or other fireworks, the cardboard shell of the firecracker explodes with a loud popping sound when the chemical burning reaction releases the gas.

What Produces the Colors of Fireworks?

Another notable feature of fireworks displays is the vibrant colors. In the USA, red, white, and blue are of course popular July 4th colors. Many other colors are also possible. What produces these colors?

Firecracker explosion: Image by ABFin the gunpowder. Burning gunpowder releases large amounts of hot gas. If the gunpowder is not confined in any way, the chemical burning reactions release the gas harmlessly, and it does not explode.

Various chemical elements mixed in with the gunpowder produce a wide variety of colors.

  • Sodium, as found in common salt, emits a strong yellow color when it burns.
  • Copper causes a blue color.
  • Chemical compounds containing the elements lithium and strontium produce a red color.
  • Compounds containing barium burn green.
  • Compounds containing the element calcium burn orange.

To produce a bright white color, the chemical reactions must burn at a very high temperature. Mixing aluminum or magnesium in with the gunpowder will produce a white hot chemical burning reaction.

Just as artists produce colors by mixing primary colors, fireworks displays can also produce colors that are mixtures of other colors. For example mixing the chemicals that produce red and blue colors will produce a purple colored firework display.

To get red, white, and blue fireworks, use lithium or strontium for the red. Use magnesium or aluminum for the white, and use chemicals containing copper for the blue.

A Red Fireworks Display Image by Bouncey2k

What Chemistry and Physics Happens in the Atoms?

The chemical burning reactions in the gunpowder in the fireworks vaporize the gunpowder and the color producing chemicals mixed in with the gunpowder. The hot gas atoms frequently collide with each other in the firework explosion.

These collisions push the electrons to higher energy levels, which are higher orbitals, in the atoms. After a short time the electrons jump back down to the lowest energy level, which scientists call the ground state.

The electrons must release the extra energy, and they release this energy as light. The color of the light depends on the exact amount of energy released when the electron jumps to the ground state.

Physicists and chemists call the specific colors of light emitted when the electrons jump to lower energy levels the emission line spectrum. Each element has its own unique colors or emission line spectrum. Engineers designing fireworks displays select the chemical elements or compounds that have the right emission line spectrum to produce the desired colors for the display.

Understanding the chemistry and physics of fireworks can increase the enjoyment of a fireworks display.

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