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Glowsticks: how do they work?

The emission of light is the only physics principle involved here, but the chemistry isn’t that hard to understand the basis of. Glowsticks work by mixing two compounds, typically hydrogen peroxide and a phenyl oxalate ester. The hydrogen peroxide is kept in a separate glass tube, which is broken when the glowstick is bent. The ester is then oxidized by the hydrogen peroxide, which creates a chemical called phenol and an unstable peroxyacid ester. That peroxyacid ester decomposes and additional phenol is released amongst a cyclic peroxy compound, which decomposes into carbon dioxide. This decompostion releases a substantial amount of energy, which is not observed without the presence of a fluorescent dye. Moving on.

The dye is the component capable of chemiluminescence, which is why light is not emitted without it. When the energy from the decomposing cyclic peroxy compound is transferred to the dye, the electrons are temporarily excited into a higher energy level and when they eventually fall back to the ground state, the loss of energy of the electron is released as a photon. The colour, or frequency of this photon depends on how much energy it is released with. The higher the energy, the further toward the violet end of the spectrum the light emitted will be. Different dyes rely on different amounts of energy to excite electrons, which is why other frequencies are emitted. 

The speed and intensity of the reaction is dependent on the chemicals used, but also the temperature. Putting a glowstick in the freezer slows the atoms’ collisions down, therefore releasing less energy over the same amount of time which causes less photons to be emitted. However, the reaction lasts a lot longer. The opposite is true for higher temperatures, where the light is brighter, but the glowstick won’t last as long. In conclusion, glowsticks are really cool.