Rainbows and Chemistry

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Rainbows and Chemistry

• Radha Pyati
• Department of Chemistry, UCCS
• Curiosity Unlimited Presentation
• Friday, November 14, 2003

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Meet a Chemistry Student

• Amber Hodges, B.S. 2003

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How Does Chemistry Create Color?

• When the electrons in certain molecules are
  excited, they absorb a particular color of light
  in the visible region of white light.
• Our eyes see the color that is roughly
  complementary to the absorbed light.
• Light absorption involves moving an electron from
  a lower to a higher energy level.

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Chemistry and Color in Manganese Compounds
Each of these manganese compounds has a different
electronic structure, so it absorbs a different
wavelength (or color) of light.
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Elements Emit Different Colors Depending on Their
Electronic Structure

• Each layer will emit flame based upon the energy
  levels of electrons in the atoms in that layer.
• These differences are characteristic of each
  elements electronic structure.

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Fire and Sparks and Molten Iron!

• Thermite reaction
• Thermite mixture of aluminum and iron(III)
  oxide (rust)
• Used in welding and explosives
• Part of Hindenburgs skin, making skin easily
  ignitable by spark (hydrogen was simply the fuel
  for the fire)
• Reaction Al Fe2O3 ? Fe Al2O3
• To provide the reaction with enough heat to
  start, permanganate oxidizes glycerin (like the
  spark that ignites the flame in a butane lighter)

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Diagram of Thermite Reaction
Glycerin
Potassium permanganate
Al Fe2O3
2 ? 2Fe Al2O3
Extremely exothermic! Gives off enough heat to
make molten iron!
Fe(l)!

• Melting point of iron 1,530C 2,786F