How to Keep Your Light Sticks Lit Up Longer

Research Questions:

• Does temperature affect the strength of chemiluminescence?
• Can heat add energy to the chemical reaction in a light stick?

On a fall night, you’ve probably seen fireflies glowing in the bushes. Fireflies use chemiluminescence, a very efficient process that converts energy to light. Light sticks use a similar process. Do you think that temperature affects how bright light sticks or fireflies can glow? This experiment will help you find out.

Materials:

• Four foam cups
• Permanent marker
• Four identical light sticks
• Four thermometers
• Stopwatch
• Graph paper, optional

Experimental Procedure:

1. Label the cups “hot,” “warm,” “cold,” and “freezing.”
2. Fill the “hot” cup with boiling water, the “warm” cup with warm tap water, the “cold” cup with cold tap water, and the “freezing” cup with ice water.
3. Drop a thermometer into each cup, and wait about a minute to make sure that the temperatures have been measured correctly.
4. Activate each light stick, and start your stopwatch at the same time.
5. Simultaneously, drop each light stick into a cup of water and stir them for one minute.
6. Turn off the lights. Compare the brightness of the sticks and record your observations. Try to rank them in terms of brightness, with “4” being the brightest and “1” being the least bright.
7. Turn on the lights again.
8. Use the sticks to stir the cups of water for exactly five more minutes.
9. Turn off the lights and compare the brightness of the sticks again. Record your observations.
10. Leave the light sticks in the cups for one hour. Then compare the brightness of the sticks again.
11. Analyze your data. You can either average the three rankings of each light stick and then compare the averages, or graph the ranks on a line graph.

Terms/Concepts: Heat Energy; Endothermic and exothermic reactions; Chemiluminescence and bioluminescence; What makes fireflies glow?; What makes light sticks glow?

References:

First Place Science Fair Projects for Inquisitive Kids, by Elizabeth Snoke Harris. Pp. 102-103.