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Chemiluminescence and Anti-oxidants
Objectives:
-to explore a chemiluminescent reaction
-to observe the effects of temperature on the rate of a reaction
-to observe the effects of anti-oxidants on the rate of a chemiluminescent reaction
Equipment/Materials
Procedure I:
2-3 green or red/orange lightsticks
ice water bath
warm water bath (temperature < 70 °C)
Procedure II:
4 green or red/orange lightsticks
1 Vitamin C tablet (250 mg or 500 mg) (no sweetener)
1 Vitamin C tablet, chewable (250 mg or 500 mg) w/
sweetner*
½ teaspoon (2.0 g) sucrose (table sugar)
Duct tape
sharp knife
masking tape and/or permanent marker
You will also need an area that can be darkened (such as a closet or interior bathroom) where the
lightsticks can be observed.
*Sweetener needs to be a sugar (such as dextrose). Artificial sweeteners such as Aspartame® will not work. Both
of the Vitamin C tablets need to be the same dosage (i.e. both 250 mg or both 500 mg.)
Introduction
Chemiluminescence
If you have ever seen the glittery display of fireflies on a summer evening or the eerie
nighttime glow produced by the wake of a boat or crashing waves in the ocean, you have
observed a chemical reaction that is releasing energy. Many chemical reactions produce energy,
typically in the form of heat. However a small class of reactions produces energy in the form of
light; these reactions are called chemiluminescent reactions. Man-made versions include the
glow sticks or lightsticks that are sold for camping, novelty, and roadside emergencies. The
biological version of this process (e.g. fireflies, glow worms) is called bioluminescence.
Chemiluminescent reactions typically involve the oxidation of a compound. The
oxidized form is produced in a chemically excited state of higher energy. As it returns to a more
stable form, it emits its extra energy as light. (See Figure 1.) The color of the light depends on
the energy gap between the excited state and the lower energy ground state. Chemiluminescence
can also result when energy from an excited molecule is transferred to another molecule. This
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second molecule then emits the light energy as it returns to its ground state. (See Figure 2.)
Most commercially available lightsticks utilize the latter process.
Commercial lightsticks typically utilize dilute hydrogen peroxide to oxidize a phthallic
ester in the presence of a dye. The high energy oxidation product transfers its energy to the dye
molecule which then emits light, as is illustrated in Figure 2. Different dyes produce different
colors. The lightstick is constructed of an outer thick plastic tube around a smaller inner tube
made of glass which contains the hydrogen peroxide. The inner tube is cracked and the two
chemicals are mixed and the reaction occurs.
L(reduced) oxidation

→
L(oxidized)high energy
light
L(oxidized)low energy
Figure 1. Schematic representation of the chemiluminescent reaction of molecule, L. The oxidized form of L is
produced in a high energy excited state. As it returns to the more stable ground state, it gets rid of the extra energy
as light.
L(reduced) oxidized
→
Mhigh energy
L(oxidized)high energy
transfer
+ M energy

→ L(oxidized)low energy +
energy
transfer
L(oxidized)low energy
+
Mhigh energy
light
Mlow energy
Figure 2. In this example the energy is transferred from the oxidized form of L to a different molecule, M. M then
returns to a more stable, lower energy form and emits light in the process. The light released in this case is often a
different color than the example in which the oxidized form of L emits light directly.
Typically, lightsticks are wrapped in an airtight, light blocking foil wrapper. If the
wrapper is damaged, light emission is reduced over time. The chemiluminescence of a
commercially available lightstick can be slowed down by cooling and accelerated by heating.
Furthermore the reaction can be inhibited by the addition of selected anti-oxidants.
Antioxidants
Antioxidants are a class of chemical compounds that are gaining increased media
coverage for their importance in healthy cellular processes. They help to rid the body’s cells of
dangerous “free radicals” which, if left unchecked, can promote oxidative processes that harm
the cell. Free radicals are a natural by-product of normal metabolism, and your body has several
mechanisms for dealing with them. However, antioxidants such as vitamins A, C, and E can also
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assist your cells in protecting against free radical damage. Ascorbic acid, or Vitamin C, is an
important water soluble antioxidant that you’ll use in this experiment.
If an antioxidant is present, oxidation reactions are inhibited. This means that they either
don’t occur at all, or occur more slowly than if the antioxidant weren’t present. Other
compounds enhance oxidation processes. Since a chemiluminescent reaction gives off light,
you’ll be able to observe the presence and absence of an antioxidant.
Procedure
I. Effect of temperature on the behavior of lightsticks.
Unwrap the lightsticks and follow the manufacturer’s instructions to initiate the reaction. This
typically involves cracking the inner glass tube by bending the outer plastic container and
shaking to mix the two solutions of chemicals.
Place one lightstick in the warm water bath. To avoid melting the plastic casing, do not exceed
70 °C. Place a second light stick in an ice water bath. The optional third lightstick can be used
as a control for comparison.
Allow the lightsticks to equilibrate to the temperature of the baths (~10 minutes). Record the
effect of temperature on the intensity of light emitting from each of the lightsticks.
II: Effect of anti-oxidant compounds on chemiluminescence.
CAUTION: In this procedure you will be using a sharp knife to
cut open the lightsticks. Use caution!
CAUTION: The chemicals contained within the lightsticks are not
toxic. However they will cause discomfort in the case of eye
contact. As with all procedures you should WEAR SAFETY
GOGGLES WHEN PERFORMING THIS EXPERIMENT.
Crush the regular Vitamin C tablet in a bowl or on a plate. Crush the chewable Vitamin C as
well, taking care to keep the two powdered tablets separate. Measure or weigh out the sucrose.
Unwrap the lightsticks and follow the manufacturer’s instructions to initiate the reaction. This
typically involves cracking the inner glass tube by bending the outer plastic container and
shaking to mix the two solutions of chemicals.
Secure one of the lightsticks vertically by stabilizing it against a wall or the refrigerator. Very
carefully (Don’t cut yourself!) cut the top of the stick ¾ of the way off. (See Figure 3.) Leave a
portion of the cap intact so it can be used to cover the tube for the purposes of mixing later in the
experiment. Use caution when cutting the top of the lightstick off both to prevent knife injuries
and to prevent the chemicals within the lightstick from splashing out. Securing the lightstick
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against a hard vertical surface is very important, as is wearing safety goggles during the entire
procedure.
After cutting into the top of the lightstick, fold back the cap and pour the sucrose into the tube.
Fold the cap back into place and seal with duct tape. Try to ensure that your seal is airtight.
Gently upend and the stick for 20-30 seconds to mix, label the tube and set aside.
Repeat the above process for each of the two Vitamin C samples.
The fourth lightstick will act as the control, but you should open the tube and seal it with duct
tape as you did the others. (Why?)
Record the relative (to each other) brightness of each of the four tubes. Note their relative
appearance after one hour, after two hours and after several hours.
Further experimentation for interested students. Read an article on antioxidants. Repeat this
experiment with some of the foods, herbs, and/or vitamins that are considered to have
antioxidant behavior.
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Copyright © 2000 by Doris Kimbrough, all rights reserved
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Download Data Sheet
Report
1. Discuss the effect of temperature on the intensity of light from the lightsticks. What
conclusions can you draw about the rate of reaction with respect to temperature? Why
does placing activated lightsticks in the freezer prolong their life?
2. Discuss the effect of the added compounds in Procedure II, on the course of the reaction.
Make a table that lists each compound and the corresponding effect on the
chemiluminescent reaction. When (if ever) was the reaction inhibited? When (if ever)
was the reaction enhanced? Provide a plausible explanation for the differences that you
observed.
3. Why did you cut open the lightstick that was acting as your control?
4. Suggest other compounds that might enhance or inhibit this reaction? Postulate as to
how you could use this reaction as a way to monitor the presence of antioxidants in
foods. If you tried any additional substances, report on your results.
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Copyright © 2000 by Doris Kimbrough, all rights reserved
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