University of Virginia
Physics Department

Chemiluminescence: The Blue Glow

A Physical Science Activity

2003 Virginia SOLs

 

Objectives

Students will

Motivation for Learning

Driving Question

Have you ever wondered how fireflies light up or what causes lightsticks to work? Both are caused by chemical reactions in which energy is released or given off as “cool” light. More specifically, these reactions involve chemiluminescence. Chemiluminescent reactions that occur in living organisms are called bioluminescent reactions.

A firefly lights up when an enzyme called luciferase (meaning “light-bearing”) in its lower abdomen reacts with oxygen to produce energy emitted as light. Lightsticks are composed of two solutions, one of which is contain in a glass tube. By bending the lightstick, the glass tube is broken allowing the two solutions to mix. The result of this chemical reaction is the glow of the lightstick.

Ideas for motivation: Decorate your classroom with pictures of living organisms such as fireflies, certain bacteria, fungi, sea animals, and insects that make chemical compounds from cells in their bodies that can produce light. (bioluminescent reactions)

Place “glow-in-the-dark” toys or items (such as stars) around the room. The stars are made of a phosphorescent pigment, which stores light that hits the surface of the stars, then releases it gradually.

Show examples of lightsticks, which are sold at sporting goods or camping supply stores. They are also sold as necklaces and bracelets at carnivals and amusement parks.

Background Information

The student activity involves chemiluminescence, which occurs when chemical energy is converted into cool light. The released energy is absorbed by electrons in certain molecules. The electron jumps (makes a quantum leap) to a higher level and is in an excited state. As the electron returns to the lower ground state, it releases energy that can be seen as a photon of light. The amount of energy is called a quantum.

In this activity, liquid chlorine bleach serves as the oxidizing agent. This means that oxygen reacts with the luminal to produce the blue light. The luminal is converted to an excited-state product (3-aminophthalate ion), which decays to the ground state and causes the release of a photon. This release is seen as “chemiluminescence.”

Due to the reactive nature of the liquid bleach, the chemical reaction occurs very quickly and the light is very bright. The light may be bright enough to see even with the lights on in the room.

Another option for this experiment is the substitute hydrogen peroxide for liquid chlorine bleach. Use a more concentrated solution than when using bleach. Also, a copper sulfate crystal or corroded penny may be used as a catalyst. 

Student Activity

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Materials

WARNING: Bleach is very reactive. It will combine and change in chemical reactions very quickly and with lots of energy. This also makes it very dangerous.

Resources:

Chemical Demonstrations: A handbook for Teachers of Chemistry, Vol. 1, by Bassam Z. Shakhashiri

http://www.scifun.chem.wisc.edu/HomeExpts/Chemilum.html

http://ice.chem.wisc.edu/materials/light/lightandcolor7.html

http://www.omniglow.com/classrm.html

Procedure

  1. Use a balance to measure 0.12 grams of luminol. First, find the mass of a piece of paper. Place the luminol on the paper and measure the mass again. Find the difference of the masses until you have the proper amount of luminol.*
  2. Make the luminol solution by dissolving 0.12 grams of luminol in 250 mL of distilled water.
  3. Make the bleach solution by mixing 25 mL of liquid chlorine bleach with 225 mL of distilled water.
  4. Place the solutions in an ice bath, but do not let them freeze.
  5. Measure the temperature of each of the solution.
  6. Darken the room.
  7. Use a funnel connected to a plastic tube and pour the contents of both beakers into the funnel at the same time. The tubing will empty into another beaker.**
  8. Measure the temperature of the mixture.

*If available, electronic balances would allow more precision.

**If the funnel and plastic tube are not being used, then simply pour the contents of both the luminol and bleach solutions into another beaker at the same time.

Data Sheet

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Temperature of luminol solution___________________

Temperature of bleach solution___________________

Final temperature of mixture_____________________

  1. Describe the solution that was made when you mixed the luminol with the distilled water.







  2. Describe the liquid chlorine bleach solution.







  3. What happened when you mixed the two solutions together?







  4. Describe the evidence that a chemical reaction occurred.







  5. Was there any difference in temperature before and after the luminol and bleach solution were mixed together?







  6. Was this an endothermic or exothermic reaction? How do you know?







  7. How might chemiluminescence be useful to living organisms such as fireflies?







  8. Name some practical uses of chemiluminescence by humans.







Extensions

Fluorescence and phosphorescence are other kinds of luminescence. Students can do research on these and present their findings to the class. (glow-in-the-dark toys; Sensodyne toothpaste)

Students can use the internet to find out several real-life applications for luminol.

Students can devise an experiment to test triboluminescence, or the production of light involving pressure or friction being applied to a crystal. (sugar crystals or wintergreen lifesavers)

Students with Special Needs

All students should be able to participate in this activity.

Click here for further information on laboratories with students with special needs.

 

Assessment

To print out the Data Sheet only, click here.

  1. What is chemiluminescence?
  2. What is the difference between an endothermic and an exothermic reaction?