Chemistry - Gummy bear sacrifice in foam city Lab
- 1. Name _____________________________________________ Date ________________ Gummy Bear Sacrifice in Foam City Introduction Today in lab we are going to look at two of my favorite reactions in an attempt to practice our skills in writing and balancing chemical reactions. The reactions we are looking at today are decomposition reactions, and combustion reactions. In a decomposition reaction, a single substance breaks down into two or more substances. We say the original substance has “decomposed” which means it has broken apart. Every decomposition reaction looks something like this. AB A + B A combustion reaction is a chemical reaction that involves oxygen and produces energy (heat) so rapidly that a flame results. This reaction occurs between certain compounds, especially organic compounds, oxygen, and hydrocarbons, which are carbon and hydrogen attached. The products of this reaction include carbon dioxide and water. Every combustion reaction looks something like this C(X)H(x) + O2 H2O (g) + CO2 (g) Foam City (Elephant’s Toothpaste) In this reaction, we will decompose hydrogen peroxide (H202) into its components using the catalyst KI. Elephant’s toothpaste observations: Write the balanced equation for the elephant’s toothpaste reaction:
- 2. Describe the elephant’s toothpaste reaction in a sentence: ___________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ ____ The Gummy Bear Sacrifice This demonstration can be used to illustrate the vast amount of energy which is available from the oxidation of carbohydrates, such as sugar. An excess of oxygen, generated by the decomposition of potassium chlorate, will react with a gummy bear and release a large amount of energy quickly and dramatically. When heated, potassium chlorate decomposes, producing sufficient oxygen to ignite the sugar in the gummy bear. Since the oxidation of the sugar is very exothermic, potassium chlorate continues to decompose to oxygen, and the rate of combustion becomes very rapid. Materials one 25x150 mm test tube one ring stand with clamp for test tube 5.0 grams potassium chlorate Bunsen burner one candy gummy bear Procedure 1. Set up the stand and clamp, and support the test tube in the clamp in a vertical position. 2. Add approximately 5 grams of potassium chlorate to the test tube (about 1 cm in depth). 3. Gently heat the tube with the burner until the potassium chlorate is completely molten. Bubbles of oxygen will begin to form. 4. Remove the burner and use crucible tongs to drop in the gummy bear, and then stand back! For added piece of mind, the reaction can be performed behind a safety shield. 5. Allow the tube to cool, and then remove from the clamp. The tube should be soaked in water for about 15 minutes and then cleaned with a brush to remove the residue. These chemicals may be washed down the drain. Gummy Bear Sacrifice Reaction Observations:
- 3. This reaction takes place in two steps, first the potassium chlorate decomposes, and then the oxygen produced from the decomposition reaction is used in a combustion reaction with the carbohydrates in the gummy bear. Write the balanced equation for the decomposition of the potassium chlorate: Write the balanced equation for the combustion reaction of the carbohydrates in the gummy bear: Describe in sentences, the complete chemical reaction that takes place in the gummy bear sacrifice reaction. (You need to include both the decomposition reaction and the combustion reaction.) _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________ _______________________________________________________________________
- 4. _______________________________________________________________________ _______________________________________________________________________ _______________ Questions 1. Why doesn’t the hydrogen peroxide or the carbohydrates react spontaneously on their own? 2. What gas is formed in the elephant’s toothpaste experiment? How could you test it? 3. What was the purpose of the soap in the elephant’s toothpaste experiment? Predict how this reaction would look of you forgot to add the soap. 4. What was the purpose of the potassium iodide? Predict what would happen if you forgot to add the potassium iodide. 5. In the gummy bear sacrifice experiment, what is the evidence that a chemical change has taken place? (Write as many as you can think of.) 6. According the law of conservation of mass, the mass of the products is equal to the mass of the reactants. If we weighed the contents of our test tubes after the gummy bear sacrifice, it would not equal the mass of the reactants that were used. How can you account for this?
- 5. Bonus: Write a short story for why the people of foam city sacrifice gummy bears. Your story must include something accurate about the science responsible for these chemical reactions