Glow Stick Experiment - Rate of Chemical Reaction

Who doesn't love playing with glow sticks? Grab a pair and use them to examine how temperature affects the rate of chemical reactions. It's good science, plus it's helpful information for when you want to make a glow stick last longer or glow more brightly.

Glow Stick Experiment Materials

• 3 Glow sticks (the short ones are idea, but you can use any size)
• Glass of ice water
• Glass of hot water 

How To Do the Glow Stick Experiment

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Are Glow Sticks Endothermic or Exothermic?

By Anne Marie Helmenstine, Ph.D.

Yes, you can just activate the glow sticks, put them in the glasses, and see what happens, but that wouldn't be an experiment. Apply the scientific method:

1. Make observations. Activate the three glow sticks by snapping them to break the container inside the tube and allowing the chemicals to mix. Does the temperature of the tube change when it starts to glow? What color is the glow? It's a good idea to write down observations.
2. Make a prediction. You're going to leave one glow stick at room temperature, place one in a glass of ice water, and place the third in a glass of hot water. What do you think will happen?
3. Conduct the experiment. Note what time it is, in case you want to time how long each glow stick lasts. Place one stick in the cold water, one in the hot water, and leave the other at room temperature. If you like, use a thermometer to record the three temperatures.
4. Take data. Note how brightly each tube glows. Are they all the same brightness? Which tube glows the most brightly? Which is the dimmest? If you have time, see how long each tube glows. Did they all glow the same length of time? Which lasted the longest? Which stopped glowing first? You can even do math, to see how much longer one tube lasted compared with the other.
5. Once you have completed the experiment, examine the data. You can make a table showing how brightly each stick glowed and how long it lasted. These are your results.
6. Draw a conclusion. What happened? Did the outcome of the experiment support your prediction? Why do you think the glow sticks reacted to temperature the way they did?

Glow Sticks and the Rate of Chemical Reaction

A glow stick is an example of chemiluminescence. This means luminescence or light is produced as the result of a chemical reaction. Several factors affect the rate of a chemical reaction, including temperature, concentration of reactants, and the presence of other chemicals.

Spoiler alert: This section tells you what happened and why. Increasing temperature typically increases the rate of the chemical reaction. Increasing temperature speeds up the motion of molecules, so they are more likely to bump into each other and react. In the case of glow sticks, this means a hotter temperature will make the glow stick glow more brightly. However, a faster reaction means it reaches completion more quickly, so placing a glow stick in a hot environment will shorten how long it lasts.

On the other hand, you can slow down the rate of a chemical reaction by lowering the temperature. If you chill a glow stick, it won't glow as brightly, but it will last much longer. You can use this information to help glow sticks last. When you are done with one, put it in the freezer to slow down its reaction. It may last until the next day, while a glow stick at room temperature would stop producing light.

Are Glow Sticks Endothermic or Exothermic?

Another experiment you can perform is to determine whether or not glow sticks are endothermic or exothermic. In other words, does the chemical reaction in a glow stick absorb heat (endothermic) or release heat (exothermic)? It's also possible the chemical reaction neither absorbs nor releases heat.

You might assume that a glow stick releases heat because it releases energy in the form of light. To find out whether this is true, you need a sensitive thermometer. Measure the temperature of a glow stick before activating it. Measure the temperature once you crack the stick to start the chemical reaction.

If the temperature increases, the reaction is exothermic. If it decreases, it's endothermic. If you can't record a change, then the reaction is essentially neutral as far as thermal energy is concerned.