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The colors of fireworks come from the burning of metallic salts. Originally, only amber from charcoal and white from gunpowder and sulfur were used. In 1630, French chemist Jean Appier added copper sulfate, which burned a green color. Later, zinc was found to burn a greenish blue. By the 1850’s, formulas for the various colors to be used in fireworks were created. Two French chemists, F.M. Chertier and Claude Ruggirei did much of this work. Many of the salts they described are still being used today: barium for green, calcium for orange, copper for blue, sodium for yellow and strontium for red. By the turn of the century, aluminum and magnesium were also being used for white.
Fireworks were not the only used for the colors given off by these salts. Scientists were using flame tests to determine the colors given off when a chemical is burned. Potassium burned purple, while lithium burned a bright red. But what caused these colors to appear?
Scientists decided it must be due to the electrons located within the atoms. When an atom is heated the electrons jump into a higher energy level. Essentially, the electron absorbs energy. Later, the electron will “fall” back into its previous energy level and release energy. This released energy is in the form of light, and in this case, colored light. Different atoms give off different colors of light.
Today, scientists can use this method to determine the substances burning at the heart of stars. For example, if a star is burning bright red, it might very well contain a high level of strontium.
1. What colors do the following substances burn?
Charcoal
Gunpowder and Sulfur
Calcium
Barium
Sodium
Potassium
Lithium
2. Explain the process of how different colors of light are produced.
3. How do scientists use these techniques today?