Gummy Bear Demonstration (Diana Van Pelt)

Title: Gummy Bear Demonstration

Principle(s) Investigated:

· Decomposition reactions

· Combustion reactions

· Exothermic reactions

Science Content Standards of California

· 9-12 chemistry 2.1.c - Distinguish reaction types, including single replacement, double replacement, synthesis, decomposition, and combustion

· 9-12 chemistry 7 - Energy is exchanged or transformed in all chemical reactions and physical changes of matter.

· 9-12 chemistry 7.b - Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.

Materials:

· Potassium Chlorate (KClO3)

· Gummy Bears

· Pyrex Test Tube

· Ring Stand

· Test Tube Clamp

· Bunsen Burner

Procedure:

1. Set up ring stand and clamp. Support test tube in clamp making sure that the mouth of the test tube is facing away from students. Raise clamp high enough so Bunsen burner can be placed underneath.

2. Add small amount of potassium chlorate (approx.1 cm high) in bottom of test tube.

3. Heat test tube with Bunsen burner until the potassium chlorate becomes a liquid.

4. Remove Bunsen burner.

5. Using tongs, drop gummy bear into test tube.

6. Stand back

Student prior knowledge:

· Students should know how to distinguish chemical change from physical change.

· Combustion reactions are exothermic reactions during which energy is released.

Explanation:

In this demonstration, two reactions occur. First is the decomposition of potassium chlorate with heat being the catalyst for the reaction:

2KClO₃(s) --> KCl(s) + 3O₂(g)

Potassium chlorate is an extremely powerful oxidizer- which means it readily transfers oxygen atoms. It is important to note that when heated, it can spontaneously react with many things. This first reaction produces an oxygen rich environment inside the test tube and when the gummy bear is added, the sugar in the gummy bear ignites.

The second reaction is a combustion reaction. The sugar rapidly combines with the oxygen releasing large amounts of energy in the form of heat and light. It is a very exothermic reaction.

C₁₂H₂₂O₁₁(s) + 12O₂(g) ---> 12CO₂(g) + 11H₂O(g) + heat + light

*Notice it’s similarity to cellular respiration.

The demonstration can be used when discussing:

· chemical reactions such as decomposition and combustion

· exothermic reactions

· metabolism of sugar or cell respiration in biology

· energy change or bond energy

· the difference between chemical changes and physical changes

Questions & Answers:

1. What causes the rapid increase in reaction rate after adding the gummy bear?

The heat that is produced when the sugar of the gummy bear ignites (combustion) causes the potassium chlorate to release more oxygen. This creates a positive feedback loop and the rate of the reaction rapidly increases.

2. What causes the lavender color in the flame during this reaction?

The lavender color indicates the presence of potassium, much like the flame test.

3. Write an equation for cellular respiration.

glucose + oxygen --> carbon dioxide + water + energy(ATP)

or

C₆H₁₂O₆ + 6O₂ --> 6CO₂ + 6H₂O + 36ATP

4. Where does the energy that is released during the reaction come from?

The bond energy inside the gummy bear (glucose molecule) is converted to a different form of energy. That being heat energy (that you can feel) and light energy (that you can see).

Applications to Everyday Life:

1. Metabolism - humans can’t survive long without oxygen. Every cell in

the body uses oxygen to oxidize sugars or other food molecules to

produce ATP. ATP is the energy that powers cell functions.

2. Combustion - we depend on combustion of fuels to power our vehicles,

heat our homes, and heat our food.

3. Matches and explosives - potassium chlorate is a strong oxidizing

agent and has been used in the production of matches, explosives and

pyrotechnics.

Photographs:

Videos: Link to demonstration video on youtube.

http://video.google.com/videoplay?docid=7433492777550198070#

References

1. "Chemistry Demonstrations, Experiments, Labs & Projects." Chemistry - Periodic Table, Chemistry Projects, and Chemistry Homework Help. Web. 14 Nov. 2010. http://chemistry.about.com/od/chemistrydemonstrations/ht/gummibear.htm

2. "Gummy Bear Demo- Teacher Notes Student Handout - Metabolism." Docstoc – Documents, Templates, Forms, Ebooks, Papers & Presentations. Web. 14 Nov. 2010.

http://www.docstoc.com/docs/59174103/Gummy-bear-demo--teacher-notes--student-handout---Metabolism.

3. Herr, Norman. Hands-On ChemistryActivities with Real-Life Applications. 1st. ed. San Francisco, CA: Jossey- Bass, 1999.