Ms. Justyna Prazuch
Mr. Joseph Cohen

Title of the lesson:

Gummy Bear Terminator

Topic: Electrochemistry

Grade Level: Grade 10 and Grade 11

Time needed: One 45-minute period

 

Science or Math background material for the teacher

This demonstration vividly and dramatically illustrates the concept of a strong oxidizer.

Chemistry curriculum in the following ways:

This can be used as a "gee whiz" demonstration, or better as an illustration of the basic idea of a strong oxidizer. If used for the latter purpose, it should be presented as part of a discussion of oxidation and reduction. The bottle label states that potassium chlorate is a strong oxidizer, and this demonstration shows what that means.

Molten KClO3 can cause very severe burns. Think of your skin or the top of the lab bench as another gummy bear. Exercise your best safety technique while presenting this demonstration. It will set a good example for your class. There is also a lot of smoke produced during the oxidation (steam and KCl?), so this experiment should only be done in a room with good ventilation.

Instructional Objectives:

SWBAT:

1.     List evidence suggesting that a chemical reaction (decomposition) has occurred.

2.     Describe exothermic reactions.

3.     Identify atoms that are oxidized or reduced through electron transfer.

4.     Identify redox reactions by analyzing changes in oxidation numbers for different atoms in the reaction.

5.     Balance equations for oxidation-reduction reactions.

6.     Describe the effect that catalyst can have on reaction rate and how this effect occurs.

National Science Education Standards met by this lesson:

Core topics: VIII.1, VIII.2, VIII.3, VIII.4, VII.5, VIII.6, VIII.7

Major Understandings: 3.2d, 3.2 e, 3.2f, 3.2g, 3.2h, 3.2i, 3.3b

Equipment and Materials:

 

Procedure:

 This demo gives an example of an extremely exothermic reaction. It is also an example of a decomposition reaction that occurs rapidly when a catalyst (heat) is used. In addition, it provides the opportunity to apply the glowing splint test to test for the presence of oxygen.

Safety Considerations:

Because this reaction is extremely exothermic, be sure to take careful consideration for the points mentioned below.

       Ensure that the safety shield is between the apparatus and your students

       Check the Pyrex test tube for any defects. If any flaws (small cracks, etc.) are present, refrain from using it.

       Make sure that you wear safety shield and a lab coat.

       Be sure to point the test tube away from you and your students.

1. Fill the test tube to a depth of about one inch with potassium chlorate.

2. Clamp the test tube in place at an approximately 45 angle.

3. Set up the ring stand-clamp-test tube assembly behind a safety shield in front of the class.

4. Connect the burner so that the test tube can be heated easily.

5. Light the burner and heat the test tube at the bottom until the solid melts (mp is around 350 C).

6.  Once the solid KClO3 has begun to liquefy, test for the presence of oxygen using the glowing splint test.

7. If the test has worked you can remove the Bunsen burner and turn it off.

8.  Stand behind the safety shield and carefully drop one gummy bear into the test tube using tongs or forceps.

9. A violent flame-shooting reaction ensues and lasts for about one minute. You class will remember it for years!

Include discussion questions and possible answers:

Key Questions:

Questions to be asked before the demo

  1. What is a decomposition reaction? 
  2. Discuss and balance the chemical equation for this reaction. 
  3. How do we test for the presence of oxygen in a reaction? 
  4. Why do we use a catalyst for some reactions? What are some examples of a catalyst? 
  5. What is the difference between an exothermic and an endothermic reaction? 

Questions to be asked during the demo

  1. Why do we use a Bunsen burner in this reaction? 
  2. Why do we do the glowing splint test before putting the Gummy Bear into the test tube? 

Questions to be asked after the demo

  1. What caused the Gummy Bear to explode? 
  2. Examine what the products are. 

Explanation:

The chemical equation of the reaction for this demo is:

2 KClO3(s)2 KCl (s) + 3 O2 (g)

1. The symbol “r”, or the word “heat” can be written above the arrow to show that heat is used as a catalyst.

2. The heat from the Bunsen burner is used as a catalyst to increase the rate of reaction. The glowing splint will re-light once there is a presence of oxygen, meaning that the decomposition reaction has begun.

3. Because this reaction is extremely exothermic, the heat given off of the reaction causes the sugar in the Gummy Bear to explode into a marshmallow-like substance.

Closure:

The gummy bear is mostly sugar, which is easily oxidized by something like molten potassium chlorate. Ideally, a balanced equation would show sucrose (C12H22O11) being converted to carbon dioxide and water while the KClO3 becomes KCl. The actual reaction does not seem to go to total completion since there is usually a little gunky residue left behind.

Assessment :  “Showdown Activity” Students answer questions without help. Teams then check and coach. Teams each have set of review cards stacked in the center of the table. Teacher select the captain of each team. Captain draws the top card and reads the question aloud. Working individually, all students write their answers. Then teammates share the answers.

Extension activities: Provide some suggestions for students who want to learn more on this topic.  These could be activities that could be done at home or online.  

Bibliography/References: (List any useful books, articles, web sites)

1. Plumb, D. (2005). Structures for Success in Chemistry, High School Activities: Kagan Publishing.

2. Amato, I. (1997). Stuff- The Materials The World Is Made Of. New York: Avon Books.

3. Myers, T. (2004). Chemistry, the Physical Setting. National Science Teachers Associations.