Archive for October 27th, 2010

Science Wednesday: How Glow Sticks Work

by Katie Bowell, Curator of Cultural Interpretation

Glow Sticks

For the past few years, every Halloween I hear a rumor that you can mix hydrogen peroxide, baking soda and Mountain Dew together to make the soda glow in the dark like a glow stick. There’s only one problem: it doesn’t work.

The videos circulating the internet showing you how it’s done are fakes, and even though Mountain Dew is already a rather disturbing glow-y green color the beverage won’t be a substitute for glow sticks any time soon.

So if Mountain Dew isn’t the secret ingredient, what does make glow sticks glow without a bulb or a battery? It’s actually pretty simple: chemiluminescence.

Chemiluminescence is a chemical reaction that makes light. There are many ways to make light, but they all involve atoms releasing photons, or particles of light, after being excited by an outside of energy. In the case of glow sticks, the source of energy comes from chemistry.

Here’s how it works. There are two chemical compounds in a glow stick: hydrogen peroxide and a phenyl oxalate ester mixed with a fluorescent dye. When the two compounds are combined in a basic solution, the atoms making up each compound rearrange themselves to form new compounds. The atoms are excited when they mix together, and those atom’s electrons temporarily rise to higher energy levels. When the electrons return to their lower levels, they release energy in the form of light.

So how does the reaction happen?

Each glow stick is composed of four parts:

  • The glow stick
  • A solution of phenyl oxalate ester and a fluorescent dye inside the glow stick
  • A thin glass tube inside the glow stick
  • A solution of hydrogen peroxide inside the thin glass tube

Glow stick diagram

It’s the combination of the phenyl oxalate ester and the hydrogen peroxide that makes a glow stick glow. Snapping a glow stick breaks the thin glass tube that holds the hydrogen peroxide and lets the solutions mix.

Glow stick chemistry

Here’s the chemical reaction broken down:

  • First, the hydrogen peroxide oxidizes the phenyl oxalate ester, creating the chemical phenol and unstable peroxyacid ester
  • The unstable peroxyacid ester decomposes, creating more phenol and a cyclic peroxy compound
  • The cyclic peroxy compound also decomposes, forming carbon dioxide
  • The decompositions release energy into the fluorescent dye
  • That energy causes the electrons of the fluorescent dye atoms to rise to higher energy levels and then fall back down to their original state, releasing energy in the form of light as they go

Here’s a video showing the chemistry behind the glow. If you feel like trying this yourself, be sure you have the supervision of someone who knows what they’re doing and always wear safety gear.

The result is a bright, chemiluminescent glow that’s the perfect accessory to any Halloween costume.


October 2010
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