Kids, will a Lightstick glow longer in hot or cold weather? Many chemical reactions produce both light and heat, such as a burning candle. When a candle is lit, its flame glows and becomes hot. It is much less common for a chemical reaction to produce light without heat. The light from such reactions is called cool light, because there is no heat. Such reactions are called chemiluminescent. Fireflies produce light without heat by a natural chemiluminescent reaction. In this activity you will examine a commercial chemiluminescent chemical reaction inside a Lightstick. Lightsticks are available at many sporting goods stores, camping supply stores, and hardware stores. Amusement parks and carnivals often have them in the shape of bracelets and necklaces. 

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

What to do:

1. Remove a Lightstick from the wrapper. What does it look like? What color is it? Is anything inside the Lightstick? [See the 1996 edition of ChemShorts for Kids for a description under “Light on a Stick”].
2. Before activation, record the date and time.
3. Follow the directions on the wrapper to activate the Lightstick (bend it just enough to break the thin glass tube inside, then shake to mix the contents).
4. Observe in a darkened room. What is the color of the glow? Does the glow come from the entire Lightstick or only from the liquid inside?
5. Immerse the Lightstick in a glass of ice water for five minutes. Does chilling affect its glow?
6. Immerse the Lightstick in a glass of warm water for five minutes. [NOTE: don’t use boiling water or place in an oven because the plastic shell can melt]. What happens to the glow with warmth?
7. Summarize how temperature affects the glow.
8. Now put the glowing Lightstick in the freezer for at least 24 hours. Does it continue to glow in the freezer?
9. Remove from the freezer and warm to room temperature. Does the glow come back?
10. How does the glow change with time? How long does it take for the glow to disappear? What could be done to preserve the glow of a Lightstick?

In this activity you observed the effect of temperature on the glow of a Lightstick. Like all chemical reactions, the reaction that produces the glow is slower at lower temperatures and faster at higher temperatures. In a Lightstick, the faster the reaction is, the longer the glow lasts. When the reaction in a Lightstick occurs at a faster rate, it uses up the reactants inside more quickly than when the reaction occurs more slowly. 

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
April 2010

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References:  http://scifun.chem.wisc.edu/HomeExpts/Chemilum.html
For additional information, see CHEMICAL DEMONSTRATIONS: A Handbook for Teachers of Chemistry, Volume 1, by Bassam Z. Shakhashiri, The University of Wisconsin Press, 2537 Daniels Street, Madison, Wisconsin 53704.