Instant Light

Introduction

Add several teaspoons of Instant Light crystals to water and watch as the solution instantly produces an eerie blue glow that will last for several minutes.

Concepts

• Chemiluminescence
• Oxidation–reduction

Materials

Safety Precautions

Please review current Safety Data Sheets for additional safety, handling and disposal information. Instant Light contains sodium perborate and sodium carbonate from Clorox 2^® (see Tips), along with potassium ferricyanide and luminol. Potassium ferricyanide will emit poisonous fumes of hydrogen cyanide if heated or in contact with concentrated acids. The powder may be irritating to mucous membranes. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron.

Disposal

Allow the Instant Light solution to fully react (stir for 15 minutes) and then flush down the drain with excess water according to Flinn Suggested Disposal Method #26b.

Procedure

1. Fill a beaker with distilled or deionized water, and place the beaker on a magnetic stirrer. The size of the beaker and amount of water is up to you.
2. Turn off the lights in your classroom.
3. Add some Instant Light crystals to the water. One teaspoon for every 200 mL of water works well.
4. The blue chemiluminescent glow will begin instantly and last for several minutes.

Student Worksheet PDF

12260_Student1.pdf

Teacher Tips

• Instant light uses Clorox 2^® as the souce of sodium perborate and base. Due to formulation variations of the Clorox 2, actual times of the chemiluminescent glow may vary greatly from one batch to another. The glow should last from 1½ to 5 minutes depending on the formulation. To enhance the glow, make sure the room is completely dark.
• Adding a small amount of a fluorescent dye along with the luminol will produce different colors of light. Try small amounts (0.005 g) of disodium fluorescein (yellowish green) or Rhodamine B (red).
• Use hot or cold water to see how temperature affects the kinetics of the chemiluminescent reaction.
• Sprinkle Instant Light crystals on a wet towel; they will light up like stars.

Answers to Questions

1. Describe what happened in this demonstration.
   

   Crystals of an unknown mixture were added to a beaker full of deionized water. The solution began to glow blue. This continued for several minutes.

2. The Instant Light mixture contained potassium ferricyanide, luminol and Clorox 2, which includes sodium perborate and sodium carbonate. Which of these chemicals served as a catalyst in this reaction?
   

   The potassium ferricyanide, which yielded a ferricyanide ion, provided the catalyst in this reaction.

3. In chemiluminescence, a molecule in an “excited” state (i.e., electrons are at a high energy level) is produced. The electrons in the molecule then must return to their stable state (i.e., lower energy level). Explain how this is linked to the production of light.
   

   When an electron drops to a lower energy level, energy must be released. This energy is released in the form of light.

Discussion

The oxidation of luminol is the best-known example of chemiluminescence. The following equation represents the reaction:

The chemiluminescence, or generation of light, actually occurs as the product (species II) changes from an activated state (electrons not occupying their lowest energy orbital) to its ground state (Species III). The excited electrons release energy in the form of light, hυ, as they return to their ground state.

In this demonstration, sodium perborate and sodium carbonate serve as the oxidizing agents. The ferricyanide ion serves as a catalyst—first activating the oxidizing agent and then assisting the electron transfer from the perborate ion to the luminol.

References

Rhonda Reist, Olathe High School, Olathe, KS, for bringing this demonstration to our attention.

Dr. Phillip Pankiewicz, Stockton State College, Pomona, NJ; presented at the 1988 NSTA Convention in St. Louis.

Shakhashiri, B. Z. Chemical Demonstrations; University of Wisconsin: Madison, 1992; Vol. 1, pp 156–167.