Discovering the Physical and Chemical Properties of Polymers by gvl14091

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									Discovering the Physical and Chemical Properties of Polymers
Jon Valasek

       Area                                   Description
Science Standards     Content:
    Content          Science as Inquiry: as a result of activities, in grades 5-8,
    Technology       all students should develop
    Professional           abilities necessary to do scientific inquiry
      Development     Physical Science: as a result of activities, in grades 5-8,
                      all students should develop an understanding of
                            properties and changes of properties in matter
                      Professional Development:
                      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:
                           involve teachers in actively investigating
                              phenomena that can be studied scientifically,
                              interpreting results, and making sense of findings
                              consistent with currently accepted scientific
                              understanding.
                           Build on teacher’s current science understanding,
                              ability and attitudes.
                      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
                           Use inquiry, reflection, interpretation of research,
                              modeling and guided practice to build
                              understanding and skill in science teaching.

Abstract              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.
Audience              Physical Science teachers, grades 5-9
Key Concepts/Skills   Process skills
                          • Make observations
                          • Make measurements
                          • Compare results


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                               • Communicate results
                             Content skills
                               • Polymer physical and chemical characteristics

Rationale                    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.”1 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.
Goals                        To teach participants how to conduct an inquiry based
                             lesson involving observation and discovery of the physical
                             and chemical properties of polymers.
Objectives                   Participants will be able to analyze and draw conclusions
                             from the their observations.
                             Participants will be able to discover the physical and
                             chemical properties of polymers.
                             Participants will be able to produce and implement a
                             lesson plan to lead their students through the discovery of
                             the physical and chemical properties of polymers.
Best Practice(s)             Learning cycle, inquiry, observation, synthesis
Content/Skills               Facilitators should be familiar with the physical and
Background                   chemical properties of polymers. See explanations of the
                             science for details.
Timeframe                    Preparation time: 120 minutes
                             Lesson time: 60-90 minutes
Materials                        • 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, a bunsen burner

1
 Taylor, Beverley, et. al , Teaching Physics with TOYS Easy Guide Edition, Terrific Science Press, Miami
University Press, Middletown, Ohio, 2005,pg8.


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                         •    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.
Preparation               • Acetone is available in finger nail polish remover.
                          • Prepare 3.0 M sulfuric acid by pouring 16.6 mL of
                             concentrated acid into 63.4 mL of water.
                          • Prepare 3.0 M sodium hydroxide by dissolving 12.0
                             grams of NaOH into enough water to make 100 mL
                             of solution.
                          • Prepare 2.5 M nitric acid by pouring 12.5 mL of
                             acid into 87.5 mL of water.
                          • Prepare 3.0 M sodium chloride by dissolving 17.6
                             grams of NaCl in enough water to make 100 mL of
                             solution.
                          • Prepare a 0.868 g/mL density solution by mixing
                             80.0 mL of ethanol with enough water to make 100
                             mL of solution.
                          • Prepare a 0.914 g/mL density solution by mixing
                             60.0 mL of ethanol with enough water to make 100
                             mL of solution.
                          • Prepare a 0.945 g/mL density solution by mixing
                             43.0 mL of ethanol with enough solution by mixing
                             43.0 mL of ethanol with enough water to make 100
                             mL of solution.
                          • Distilled water should have a density close to 1.00
                             g/mL.
                          • Prepare a 1.09 g/mL density solution by dissolving
                             12.0 grams of sodium chloride in 88.0 mL of
                             distilled water.
                          • Prepare a 1.25 g/mL density solution by dissolving
                             54.0 grams of sucrose in 46 mL of distilled water.
                          • Prepare a 1.48 g/mL density solution by dissolving
                             45 grams of potassium carbonate in 55 grams of
                             distilled water.
                          • Prepare a biodegradable container by cutting the
                             base of a 2.0 L soda bottle. Invert the top into the
                             base and fill the bottle with moisten soil. The soil
                             can be enriched with lime, worms, or other
                             materials that would simulate what is found at a
                             dump site.
Safety and disposal   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



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             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.
Procedures   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



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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, 3 M 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.



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                     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.
Assessment           The participants should show through lesson plans and
                     student work the implementation of the activity into their
                     course.
Explanation of the   The densities of the polymers are as follows:
Science              Recycle code 1, PET, polyethyleneterphthalate, 1.39 g/mL
                     Recycle code 2, HDPE, high density polyethylene, 0.95-
                     0.97 g/mL
                     Recycle code, 3, PVC, polyvinylchloride
                     Recycle code 4, LDPE, low density polyethylene, 0.92-
                     0.94 g/mL
                     Recycle code, 5, PP, polypropylene, 0.90-0.91 g/mL
                     Recycle code, 6, PS, polystyrene, 1.05-1.07 g/mL
                     PMP, poly-4methyl-1-pentene, 0.83 g/mL
                     Plexiglas, polymethyl metacrylate 1.24 g/mL
                     PTFE, Teflon, polytetrafluoroethylene, 2.2 g/mL
Extensions
Equity               Be sensitive to gender, ethnic, and religious backgrounds.
Additional           N/A
Considerations
Credits/References   This exercise was modified from Polymers: A General
                     Experiment in Polymer Chemistry, Robert Liscomb,
                     National Science Teachers Association, 1997, pp 203-205

LESSON PLAN TEMPLATE

Learning Outcomes for Students: What do you want students to know and be

able to do?




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Activities Done by the Teacher:




Activities Done by the Students:




Materials Needed:




Safety Concerns:




Assessment of the Students’ Learning:




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