Author: Jon Valasek
In this lesson participating teachers will be led through an exercise using their observation skills to discover the physical and chemical properties of polymers. This is an example of an inquiry based lesson, whose methodology can be adopted in other lessons. No prior knowledge of polymers is necessary. The instructor for this exercise should be familiar with resources that define the physical and chemical properties of polymers, given in the Explanation of Science section.
In this activity facilitators will need to gather polymers from various food containers, recycling codes 1 through 6. Cut each type into small pieces and place in separate containers.
Facilitators will need the following reagents: distilled water, ethanol, acetone, 3.0 M sulfuric acid, ethyl acetate, 3.0 M sodium hydroxide, 2.5 M nitric acid, mineral oil, and 3.0 M sodium chloride.
Potassium carbonate, sodium chloride, and distilled water.
Electronic balances or else use large pieces of polymers and manual balances to determine their densities.
Alcohol lamps or candles.
Beakers or small containers to hold reagents.
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.
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.
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:
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.
AHave 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.
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.
Teaching with inquiry can be defined as giving: "students ample opportunities to apply the reasoning and procedural skills of scientists while learning the principles and concepts of science along the way." Typically teachers use activities as a way to introduce students to new concepts. This exercise is designed to lead teachers in a series of observations to discover the physical and chemical characteristics of polymers. Once the teacher feels comfortable with this activity, he/she can guide his/her own students through the same process and allow them to become more independent and actively involved in their own learning processes. Also this activity can lead to lessons on recycling and recyclable materials.
Content, Technology, and Professional Development:
Science as Inquiry: as a result of activities, in grades 5-8, all students should develop:
Physical Science: as a result of activities, in grades 5-8, all students should develop an understanding of:
Standard A: Professional development for teachers of science requires learning essential science content through the perspectives and methods of inquiry. Science learning experiences for teachers must:
Standard B: Professional development for teachers of science requires integrating knowledge of science, learning, pedagogy, and students; it also requires applying that knowledge to science teaching. Learning experiences for teachers of science must
Preparation time: 120 minutes
Lesson time: 60-90 minutes
Specific information on the reagents can be found at www.ilpi.com/msds/index.html Your should use the following precautions with acids and bases: avoid contact with skin, eyes, and mucous membranes. If you come in contact with the acid, base or acetone flush with plenty water and if the eyes are affected see a physician. Do not breathe acetone vapors. Wear goggles, aprons, and gloves when handling these chemicals. Solutions should be neutralized and poured down the drain with plenty of water. Acetone and ethyl acetate can be put under the fume hood and allowed to evaporate.
The participants should show through lesson plans and student work the implementation of the activity into their course.
The densities of the polymers are as follows:
None available for this module.
None available for this module.
Be sensitive to gender, ethnic, and religious backgrounds.
None available for this module
This exercise was modified from Polymers: A General Experiment in Polymer Chemistry, Robert Liscomb, National Science Teachers Association, 1997, pp 203-205