Group Members:
Emily Yang
Deborah Ohiani-Jegede

Chemical Colors

Chemical Colors from Jegede on Vimeo.

Chemistry Background Information
When two molecules react chemically so that there is a release of energy (an exothermic reaction), that energy sometimes manifests itself not as heat but as light. This occurs because the energy excites the product molecules into which it has been funneled and a molecule in this excited state either relaxes to the ground state, directly emitting light, or transfers its energy to a second molecule, which becomes the light emitter. This process is referred to as chemiluminescence.
All of our experiments featured the oxidation of luminol which is a chemiluminescent reaction. To exhibit its luminescence, the luminol must first be activated with an oxidant. Usually, a solution of hydrogen peroxide (H2O2) and a hydroxide salt in water is used as the activator. In the presence of a catalyst such as a copper compound which is what we used in our experiment. A catalyst is any substance that accelerates the rate of a reaction without The hydrogen peroxide is decomposed to form oxygen and water.When luminol reacts with the hydroxide salt, a dianion is formed. The oxygen produced from the hydrogen peroxide then reacts with the luminol dianion. The product of this reaction, an organic peroxide, is very unstable and immediately decomposes with the loss of nitrogen to producing a compound called 3-aminophthalate. The electrons in the 3-aminophthalate are in an excited state. Blue light is emitted as energy is released when the electrons return to the ground state


In addition to Copper and its compounds, other substances can catalyze the luminol reaction. Iron and Iron compounds, horseradish, and bleach also cause the solution to glow. In fact luminol can be used to detect blood at crime scenes because of this characteristic. The luminol solution is sprayed where blood might be found. The iron from the hemoglobin in the blood serves as a catalyst for the chemiluminescence reaction that causes luminol to glow, so a blue glow is produced when the solution is sprayed where there is blood. Only a tiny amount of iron is required to catalyze the reaction. The blue glow lasts for about 30 seconds before it fades, which is enough time to take photographs of the areas so they can be investigated more thoroughly.

Light, in general, is produced in a similar manner to chemiluminescent reactions. Light is produced in quantized amounts by the displacement of electrons in individual atoms.Electrons circle the nucleus in fixed orbits ;however when atoms are energized, the electrons "jump" from one every level to another before returning to their ground state level. A photon of light is produced whenever an electron in a higher-than-normal orbit falls back to its normal orbit. During the fall from high-energy to normal-energy, the electron emits a photon -- a packet of energy -- with very specific characteristics. The photon has a frequency, or color, that exactly matches the distance the electron falls (its wavelength).


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Additional Resources: on electrons and how they emit light

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