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Chemistry
The Chemistry of Fireworks Colors
Metal salt emission spectra and electron transitions
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Fireworks colors come from chemistry, not from dyes or paint. Inside each firework star are metal salts, fuels, oxidizers, and binders packed into small pellets that burn in the sky. When the mixture ignites, it reaches high temperatures that excite electrons in metal ions. As those electrons fall back to lower energy levels, they release photons with colors set by the element.
Key Facts
- Strontium salts produce red light, often from Sr2+ emission.
- Copper compounds produce blue light, but blue is hard to maintain because copper species can break down at high temperature.
- Sodium salts produce intense yellow light, especially near 589 nm.
- Barium salts produce green light, commonly from Ba2+ emission.
- Photon energy is related to color by E = hf = hc/lambda.
- An oxidizer supplies oxygen for combustion, while a fuel releases energy as it burns.
Vocabulary
- Metal salt
- An ionic compound containing a metal ion that can emit characteristic colors when heated in a flame.
- Emission spectrum
- The specific set of wavelengths of light released by excited atoms or ions of an element.
- Excited state
- A higher energy condition of an atom or ion in which an electron has absorbed energy.
- Photon
- A packet of light energy released when an electron drops to a lower energy level.
- Oxidizer
- A chemical that provides oxygen or another electron-accepting species to help fuel burn rapidly.
Common Mistakes to Avoid
- Thinking fireworks colors come from colored powder, which is wrong because the visible color mainly comes from light emitted by excited metal ions.
- Assuming hotter always means brighter blue, which is wrong because blue-producing copper compounds can decompose if the flame is too hot.
- Mixing up sodium and strontium colors, which is wrong because sodium gives a strong yellow emission while strontium salts are used for red.
- Ignoring the oxidizer, which is wrong because the fuel needs a chemical oxygen source to burn fast enough inside a firework star.
Practice Questions
- 1 A sodium emission line has wavelength 589 nm. Using c = 3.00 x 10^8 m/s and h = 6.63 x 10^-34 J s, calculate the energy of one photon.
- 2 A firework star contains 12.0 g of mixture that is 25.0% strontium nitrate by mass. How many grams of strontium nitrate are in the star?
- 3 A designer wants a deep blue firework and considers increasing the burn temperature as much as possible. Explain why this may make the blue color worse instead of better.