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The Challenge: Make fireworks

What range of colors is available?

The main colors produced by fireworks are yellow, orange, red, green and blue. Yellow is produced via atomic emission. The other colors in fireworks are produced by a combination of atomic emissions and molecular emissions.

Animation showing Atomic Emissions and Molecular Emissions

When you heat a substance, the heat energy can go into the electrons of the atoms or molecules. The heat raises the energy of the electrons. As they fall back to a lower energy they give off photons. The energy of these photons, and hence their wavelengths, differs between substances and so we see a range of colors.

Molecules have another way of absorbing or radiating energy. Energy can be stored by the vibrations of the different parts of the molecule. Whole atoms, or groups of atoms, can vibrate relative to each other. The overall color that we see from an excited substance is a combination of the atomic and molecular energy changes. Red is the lowest-energy visible light, so in a red-hot object the atoms are just getting enough energy to begin emitting light that we can see. If you apply enough heat energy the electrons will generate all the colors and appear white.