A LESSON PLAN ON THE CHEMISTRY EXPERIMENT CARRIED OUT AT DAUGAVPILS SECONDARY SCHOOL NO. 3 IN LATVIA

GLOW STICK REACTION

Introduction

            Glow sticks have wide recreational use, but they were originally patented as a signalling device. This function is different from molecular chemical signalling – glow sticks were intended as emergency flares minus the open flame. Their reliable light source could be deployed in an emergency or by first responder services. Military personnel, divers, police and fire fighters were equipped with glow sticks to illuminate their fields of operation.

Some chemical reactions release energy; the chemical reaction in a glowstick releases energy in the form of light. The light produced by this chemical reaction is called chemiluminescence.

There are three components of a glowstick. There need to be two chemicals that interact to release energy and a fluorescent dye to accept this energy and convert it into light. Although there is more than one recipe for a glowstick, a common commercial glowstick uses a solution of hydrogen peroxide that is kept separate from a solution of a phenyl oxalate ester together with a

fluorescent dye. The colour of the fluorescent dye is what determines the resulting colour of the glowstick when the chemical solutions are mixed.

Specifically, the chemical reaction works like this: The hydrogen peroxide oxidizes the phenyl oxalate ester, to form phenol and an unstable peroxyacid ester. The unstable peroxyacid ester decomposes, resulting in phenol and a cyclic peroxy compound. The cyclic peroxy compound decomposes to carbon dioxide. This decomposition reaction releases the energy that excites the dye.

Objectives: To recreate reaction used in commercially available glow sticks and learn the mechanism of chemiluminescent processes.

Equipment:

  1. ≈ 5 ml Glass Bottle with a Screw Cap
  2. 3 ml Polystyrene Pipets

Reagents:

  1. Ethyl acetate, 5 ml
  2. Hydrogen peroxide (35% water solution), 2 ml
  3. TCPO, 100 mg
  4. Dye, 2 mg (Rhodamine 6G; 9,10-diphenylantracene; Rubrene)

Experimental procedure:

  1. Add TCPO powder to the test tube with a screw cap.
  2. Add dye, followed by sodium acetate and ethyl acetate.
  3. Close test tube with a screw cap and shake it gently for a few seconds.
  4. Add hydrogen peroxide solution to the mixture, close test tube and shake it again.

Precautions:

Hydrogen peroxide is corrosive and can cause skin burns. Ethyl acetate is moderately toxic and can absorb through the skin and respiratory organs. TCPO can irritate skin and eyes.

Use all safety equipment (lab googles, protective gloves, lab coats).

Expected results:

Participants have learned how to recreate reaction used in glow sticks and know general mechanisms according to which the reaction proceeds.                                                            

 

Resources:

https://www.goldbio.com/articles/article/the-science-and-history-of-glow-sticks

https://www.thoughtco.com/how-do-lightsticks-work-607878