Glow-in-the-dark Chemistry

By Amy Cowen on October 27, 2011 10:53 PM

Glow-in-the-dark items can be fun year-round, but the eerie glow of a chemiluminescent reaction like the one shown here fits right in at Halloween! Image: Wikipedia.

It wouldn't be Halloween in many houses without an assortment of light-up sticks. My kids call them "glow sticks," and though they don't last all that long, they're always fun for trick-or-treating. Really, they're fun throughout the year. Many bedtime hours are interrupted by the discovery of a forgotten canister of glow sticks, all of which simply have to be activated right then. (Why is one at a time never enough? Mom logic says that the canister could last an entire week rather than just a few minutes of snapping and a few hours of glowing. Kid logic says differently!)

When I was growing up (back in the nineteen hundreds, as my kids like to remind me), glow sticks were more a safety feature. You kept light-up sticks on hand in the house for emergencies or power outages. I remember them being thicker, brighter, typically neon green, and not intended as a toy. But, getting to break out and break up a light-up stick was always a treat—even if it meant the electricity was out!

Today, glow sticks are everywhere. Circuses. Ball games. Concerts. Amusement parks. Today's sticks appear in many colors and are thinner and less expensive. No longer are these sticks destined to be tucked away for a cool-Mom-rainy day or a true blackout. They're good for anytime. Did I mention they're thinner? And cheaper?

Tale of a Stick Gone Bad

A stash of glow sticks turned up in my house recently, which meant some bedtime procrastination, all in the name of 'glow' fun. As the tube of sticks was divvied up and activated, one of them broke during the bend-and-crack phase. The snapping of the sticks, of course, is one of the cool things about glow sticks. The sensation of breaking the inner core, breaking it again, and again, and again until the core is completely liquefied is undeniably fun.

We didn't realize the outer plastic casing had broken on one until the lights were turned off, and we realized a set of hands were dotted with a few specks of 'glow.' With the lights back on, we tried to see where the 'glow' had come from. My young detective waved the stick all over the place and shook it hard, trying to reveal the break. While the leak wasn't large, it was there. When we turned the lights off again, the rug showed a star-studded smattering of glow dots from the shaking. Bending the stick a bit more, we finally saw where the liquid was escaping, and we "drew" on a paper towel with it for a bit, the neon liquid the ink on our white paper towel—a glowing signature.

Even a broken glow stick can be fun.

But they don't last all that long.

And, really, they aren't all that bright.

Turn those statements into questions, apply a bit of electronics know-how, and you're all set for a cool and illuminating science project!

Measuring 'Glow'

The Measure Luminescence in Glow-in-the-Dark Objects chemistry Project Idea lets you put the 'glow' in glow sticks to the test. Just how bright are they? For how long? And does it make a difference if you crack them open in hot weather or in cold?

In this science project, you can find out!

What's Going On In There?

At the heart of a glow stick is a chemical reaction that starts when you twist or bend the stick. A reaction between two of the chemicals in the stick releases enough energy to "excite" the electrons in the fluorescent dye causing a fluctuation in energy levels and the release of light—the chemiluminescence and the "ahhhh" moment in the dark.

In this project, you are guided through the assembly of a light detector, a circuit that lets you measure the light produced by these sticks. The sticks themselves will be closed up in a jar. You might miss seeing the 'glow,' but you'll get a lot of satisfaction tracking the readout on the light sensor—and knowing you built the circuit yourself!

Still... make sure you stock up on some extra glow-sticks, just for fun! And, once you're done with the experiment, you can re-use the jar from the project (without the foil covering), cut open a bunch of cracked and glowing sticks, dump the contents together in the jar, and enjoy an unusual "night light" for a few hours!