Elephant+Toothpaste

Amanda Palenchar (alp303@psu.edu) Leanna Feeney (lef5039@psu.edu)


 * 1. Elephant Toothpaste**

This lesson is developed for middle school students of grade level six through eight and covers the topic of catalysis. The student will be introduced to catalysis via the demonstration of a reaction with and without a yeast catalyst. The students will be able to observe that the reaction proceeds faster with the catalyst and produces “elephant toothpaste” quicker.
 * 2. Grade Level and Topic:**

• Develop descriptions, explanations, predictions, and models using evidence. - Students should be able to base a prediction on what will happen when a “mystery substance” is added to one of the two trials of the experiment. • Think critically and logically to make the relationships between evidence and explanations. - Students should be able to receive an explanation of a catalyst and what it does to a reaction and relate that knowledge to the fact that when yeast was added to the second trial of the reaction, the reaction did in fact happen faster.
 * 3. National Science Education Standards:**

• 3.2.7B: Relate energy sources and transfers to heat and temperature. - The students will be able to feel the bottle that the reaction is done in and notice that it is warm. They will then be able to postulate that the heat was generated by the reaction and the reaction gives off energy in the form of heat.
 * Pennsylvania Education Standards:**


 * 4. Instructional Objectives:**

As a result of this lesson, students should be able to recognize that the reaction is exothermic because gives off heat. This will be able to be seen by the students because the reaction container will feel warm. Also, the students will be able to understand that a catalyst speeds up the reaction. This will be depicted by performing the reaction once without a yeast catalyst and once with, showing the students that elephant toothpaste can be made quicker with a catalyst.


 * 5. Content Explanation:**

The content of this experiment will cover exothermic reactions and catalysis. The students will first discuss chemical reactions and energy (how some reactions can either produce or consume energy). The students will then be given a fictional story starring an elephant that needs to brush his teeth. The students will be told that we will be making two batches of toothpaste, one with a secret ingredient and one without, and will be asked to write a prediction for the batches. The demonstration will then be performed. The students will be able to feel the reaction chamber to see that the bottle is warm and will then be able to discuss exothermic reactions. Because the bottle with “the secret ingredient” will have reacted faster than that without, the students will then also be able to discuss why this may have occurred (catalysis).

In order to manage the activity, before performing the actual experiment with the Elephant toothpaste/catalyst reaction, the students will be provided with a short story to catch their attention and allow for application. They will then be presented with their material and safety classes and asked to identify what they have in front of them. All materials will have labels on the bottom so student can first predict and then check. The only unlabeled substance will be our “mystery substance” the yeast catalyst. The student will then be presented with information on chemical reactions involving water and peroxide. An inquiry-based discussion will occur promoting accurate predictions for what will happen with and without the yeast substance. After the demonstration occurs, student will be asked to explain whether their predictions were correct. Then they will be ask to feel the bottle, that we will first check to make sure the temperature is not too warm. Students will then ask what they believe is happening and discuss why heat may be given off.
 * 6. Administrative Considerations **

Have students put on their safety glasses. The students should have a pair of cake pans, plastic bottles, Dawn in small cups, food coloring, 1/2 cup peroxide, and one of the dissolved yeast mixtures. Stand the bottle up in the center of the cake pan. Put the funnel in the opening. Add 3-4 drops of food coloring to the peroxide and pour the peroxide through the funnel into the bottle. Show a water molecule diagram and a peroxide molecule diagram, pointing to the extra oxygen that will be set free in the reaction. Explain the reaction to them. Add the Dawn detergent to the peroxide in the bottle. Ask the children to make a prediction of whether or not the yeast will have any effect at all on the reaction. (Will it be the same, speed up, slow the reaction?) Ask them to give reasoning for their prediction. Pour the yeast mixture into one of the bottles and quickly remove the funnel. The students can touch the bottle to feel any changes that take place. Prevent them with a question on why the bottle may be warm.
 * 7. ** **Materials, Equipment, & Set-up**
 * 16 oz empty plastic soda bottle (preferably with a narrow neck such as those made by Coca-Cola)
 * 1/2 cup 20-volume hydrogen peroxide (20-volume is 6% solution, purchased from a beauty supply store)
 * Squirt of Dawn dish detergent
 * 3-4 drops of food coloring
 * 1 teaspoon yeast dissolved in approximately 2 tablespoons very warm water
 * Funnel
 * Foil cake pan with 2-inch sides
 * Safety glasses

a) **Predict: (5 minutes)** The students will then be given a fictional story starring an elephant that needs o brush his teeth. The students will be told that we will be making two batches of toothpaste, one with a secret ingredient and one without, and will be asked to write a prediction for the batches. The students will be working in groups of 2 or 3. Together they will work through their thoughts and then we will come together as a whole. They will follow a think-pair-share format to come to conclusions together. b) **Observe** (3-5 minutes): The students will observe first the demo without toothpaste and then with. Safety goggles will be worn and we will ask them to not touch the reaction while it is occurring. We will ask them to write down any differences seen and why they believe this is so. c) **Explain** (approximate time frame): The student will be presented with information on chemical reactions involving water and peroxide. An inquiry-based discussion will occur promoting accurate predictions for what will happen with and without the yeast substance. Information of the effects of a catalyst will also be given after some of their predictions have been shared.
 * 8.** ** Body of the Lesson (POE): **