Chemistry

Glow Stick Kinetics

October 10, 2013

Want to illuminate the concepts of kinetics? Try Glow Sticks! Glow sticks are a very popular accessory around Halloween because they are cheap, portable and they give off a ghostly glow. But do students understand the chemistry behind the plastic tube that gives them light? 

The "glow" from a glow stick is the result of a process called chemiluminescence - a chemical reaction that provides the energy to emit light. A glow stick is housing for two separate chemical solutions. The outer plastic chamber contains a mixture of a phenyl oxalate ester and a fluorescent dye. The inner glass vial contains hydrogen peroxide. When the glow stick is bent, the glass vial breaks releasing the hydrogen peroxide and activating the reaction.

Students familiar with glow sticks will remember that the light fades over time. This fading provides a perfect backdrop for introducing students to kinetics.

 

Initial Investigation

To study the glow stick fading, you can use a Light Level Sensor. Create a reaction vessel using a Calorimeter Cup and some black electrical tape.

Calorimeter Cup, Glow Stick, Electrical Tabe and Light Level Sensor

 

Tape the Calorimeter Cup to ensure a dark baseline. Leave a hole in the top for the Light Level Sensor.

Light Level Sensor over Reaction Vessel

 

Create a graph of Light Level vs. Time using SPARKvue®  software.  Remove the reactants from the plastic casing to eliminate interference with the Light Level Sensor. 

CAUTION: The reactants are non-toxic and non-flammable, but contact with skin or eyes may cause discomfort. In case of contact, rinse with water. Reactants can also permanently stain clothing or furniture. Use appropriate precautions.

Carefully cut a hole in the top of the glow stick and pour the phenyl oxalate ester and fluorescent dye mixture into a small beaker. Then break the glass vial and pour the hydrogen peroxide into the small beaker.  

Glow Stick reaction

 

Cover the reaction vessel with the lid and the Light Level Sensor, and start data collection.

Room Temp Glow stick light level

The light intensity is decreased to half its original value after about 5 minutes.

 

Exploration

Now that it is established that the reaction can be studied with the Light Level Sensor, you can ask your students to explore factors that would affect the reaction. Some possible ideas for exploration could include:

  • Can you make the reaction brighter?
  • How does temperature affect the reaction?
  • Does the concentration, or amount of reactants affect the reaction?

For example you could have the students look at temperature. Create a hot water bath. Cut the top off of the glow stick and heat it up in the hot water bath.

 Hot water bath

 

Once the hot water bath with the glow stick has reached a sufficient temperature (about 600C), pour some of the hot water into the Calorimeter Cup. Add a Fast Response Temperature Probe to the water in the Calorimeter Cup.  Build a page with a graph of Light Level vs. Time and digits display of Temperature. Prepare the glow stick components as before and start data collection.

Glow Stick - high temperature reaction

The initial light level is much higher than the room temperature glow stick, and the reaction happens at a much faster rate. 

 

Using the Light Level Sensor, a Calorimeter and a glow stick provides a unique way to to explore kinetics with materials that are both familiar and fun!

 

Questions or Comments: Please contact me at chemistry@pasco.com

 

Related Products:

  • PASPORT Light Level Sensor (PS-2177)
  • SPARKvue Site License (PS-2400)
  • Calorimetry Cups (6) (TD-8825A)
  • PASPORT Fast Response Temperature Probe (3 pack) (PS-2135)