Author: Jon Valasek
The following is a guide that the participants will use to conduct the exercise. However, they should be encouraged to modify the instructions below to conform to the learning cycle model and inquiry practices. This exercise should be changed to make use of the resources available. If a fume hood is not available then delete that portion of the procedures that requires that equipment.
Engagement: Polymers are all around us. Polymers are versatile as you note from the various uses in the materials around and on you and resource efficient as polymers consume only 4 percent of the world's oil supply. Polymers reduce oil consumption and carbon dioxide emissions. This investigation focuses on the physical and chemical properties of polymers. Facilitators will ask participants what physical and chemical characteristics of polymers they would test. Ask each group to brainstorm the question.
Assessment: After the brainstorming have each group report their findings to the group. Make a list of these and arrive at agreement. The list might include: physical appearance, density, strength, solubility, chemical reactions, combustion, melting, and biodegradability. These are the areas you are planning to have them explore. If others are suggested say that you did not bring materials for those investigations.
Exploration: Next have the participants devise test procedures for each investigation. A sample set of procedures follows. You might have to guide them to use solutions of known densities to determine the density of their polymer because polymers are light and their volumes are hard to measure.
Sample procedures. You will be given a sample of a polymer from your teacher. For each polymer perform the following:
- A. Describe the polymer to include color, hardness, flexibility, opaque or transparent, odor, etc. and record your observations on the data sheet. Compare your results.
- B. Determine the density of your sample by placing the sample in the test solutions provided by your teacher. Record whether the sample sinks or floats in each solution and decide the approximate density. To find a more precise density for each sample, mass your sample, find the volume by water displacement, then divide mass by volume to calculate density. Compare your results with the tests you preformed at the beginning of this procedure.
- C. Determine the strength of your sample by attempting to tear, bend, twist, or stretch it. Record your results for each sample. What happens when you hit your sample with a hammer?
- D. Use the fume hood and place a small piece of your sample in the second blue flame of a Bunsen burner. That is the part of the flame further from the barrel. Observe and record results.
- E. Introduce your sample close to a candle flame. Make observations and record results.
- F. Place 10 mL of each of the following in separate test tubes or glass containers: water, ethyl alcohol, acetone, ethyl acetate, 3M sulfuric acid, 3M nitric acid, 3M sodium hydroxide, 3M sodium chloride, and mineral oil and then add a small piece of your sample to each container. Stopper test tubes or place the lid on the glass containers. Make initial observations and then record results after 30 minutes, and 24 hours.
- G. Place a piece of your sample in the "Is it biodegradable" container and observe monthly.
Assessment: Have groups compare their test procedures and arrive at agreement on which procedures they will use and how they will document the test results. This could be in the form of tables or narratives but all participants need to agree on the same format. Discuss why that is important.
Explanation: Have participants compare results and communicate their findings to the entire group. Have the participants discuss how they would insure that their students should communicate their results. Conduct a discussion about various kinds of polymeric materials and the physical and chemical properties of each.
Assessment: Check the participants' findings and reports for accuracy and completeness.
Elaboration: Have participants develop a plan (see below) to implement this activity into their science courses. Possibly they could have groups of students form companies and test unknown polymers to determine their identity. Also the participants could plan for their students to adopt a polymer and generate a report which would include the test data. Also teachers could help form student advocacy groups for polymer use and education.
Assessment: Have groups correctly identify unknowns. Have participants give oral reports on their advocacy efforts.