Classroom Activities
In previous lessons and activities, students were presented concepts of chemical bonding, chemical reactivity, molecular structure and solution chemistry. The activities offered in this unit will extend the student's understanding of these concepts while developing others. The goal of the unit is to teach students about polymers while assisting them in understanding their physical world. The activities will be supplemented with text resources and multimedia. Formative assessment will be conducted throughout, using interactive notebooks and check in exercises.
Day 1
Students explore natural and synthetic materials. They will categorize materials based on physical properties. Materials will be sorted as natural and synthetic. Introduce the term "polymer." Introduce "hair" as an example of a polymer. Students will view the film clip "Good Hair". Students will record comments and notes in interactive journals. Qualitative mini-lab: How do hairs Fibers compare?" Students will compare types of hair.
Day 2
Explicit instruction – Prezi or PowerPoint presentation "What is a polymer – polymeric structure?" Re-loop: hair is a polymer.
Qualitative lab: How do hairs Fibers compare?" Students will compare synthetic hair fibers and textile fibers. Use guided questions to facilitate in-group discussions. Students will record observations and comments in an interactive journal. Students will create 3D models of polymer structures (cross linked, branched, linear) using Velcro and synthetic hair, sketch models and record in journals. Pair-share using guided questions. Whole class board meeting – Debrief activity: "How do hairs Fibers compare?" via board meeting and poster session. Use Oral report evaluation.
Day 3
Explicit instruction, Prezi or PowerPoint – homopolymer and copolymer use mini lab- Building simply polymers using gummy bears/marshmallows as mers.
Explain that synthetic hair is a copolymer.
Day 4 and 5
Lab – Making polymers.
Students will make, plate and test 2 types of polymers: Slime and cornstarch plastic
Day 7
Culminating activity: Testing synthetic hair fibers sing various solvents: acetone, water, acid solution, base solution, oil, peroxide.
Testing mechanical and thermal properties of synthetic hair fiber
Three techniques: heating to add curl, to remove curl, and using a flat iron with water and without.
Activity 1: Comparing Everyday Materials
Introduction to polymers
Objectives: Students will compare the properties of various materials and identify as natural or manmade.
Display several samples of polymeric materials (10-15) – oil, paper, synthetic hair, rope, yarn, bottle, corn syrup, acrylic nails, marshmallows, tape, denim, cereal, gelatin, glue sticks, rubber bands, coffee stirrers, etc. Have students to make a data table with the following categories in their interactive journals
- Type of materials
- Distinguishing properties
- Natural material
- Manmade material
Encourage students to use a hand lens and other appropriate tools to observe the properties of the materials. Have the students record all their observations and predictions in the table
Ask students to compare data tables and use guided questions to engage students in small group discussions. Students' response to guided questions should be recorded in the journal. Examples of questions: What similarities or differences are observed in the samples? What materials could be considered, both synthetic and natural? What common properties do all synthetic materials share? What common properties do all natural materials share? Allow students a few minutes to discuss their observations and predictions with each other. Afterward, have a few students share data. Explicit instruction: Describe and define polymers. Select five to seven materials, including synthetic hair and natural hair, from the listed materials and display their molecular structure on the board or in a power point slide. Molecular structures can be downloaded from Google images or created using software chemsketch: http://www.brothersoft.com/acd-chemsketch-133131.html Point out to students the repeating units in each molecular structure. Explain to students how each material observed is a polymer. Reference molecular structures of natural hair and fibers (polyesters, polyvinyl) used in synthetic hair. Introduce the unit, the objectives and the rationale to the students. Use an appropriate clip of the film "Good Hair" to further support the rationale and to spur student discussion.
Students will record their comments and notes on the film in their interactive journals.
Activity 2: How do hair "fibers" compare?"
Objectives: Students will
- compare the properties of synthetic hair fibers and textile fibers
- describe the fibers' texture, strength (break ability), elasticity, etc.
- create 3D models of polymer structure
Have students to make a data table with the following categories in their interactive journals
- Type of materials
- Visual representation
- Distinguishing properties with subcategories – texture, strength, elasticity
Encourage students to use a hand lens and other appropriate tools to observe the properties of the materials. Students record observations and comments in interactive journal. Use guided questions to facilitate in-group discussions. Students' response to guided questions should be recorded in the journal. Examples of questions: What makes each of these materials different? What do the properties suggest about the structure of the materials? How does structure effect function? What properties do the fibers share? Explicit instruction: Debrief activity with whole class. Use power point or Prezi to help students relate activity to content. Use background information on polymeric structure to create Prezi or power point. Images of polymeric structures can be found in General Chemistry textbooks or through Google images. Allow to time to answer clarifying questions. In the next section of the activity, students will create 3D models to represent polymer structures – branched, linear, and cross linked. Provide students Velcro, synthetic hair, 2 ring stands, 2 clamps, 1 cross bar, scissor, and images of polymeric structure. Assist students in building models by showing a prototype. Advise students that Velcro should be used for the links or branches, and you can recommend a maximum number of Velcro links. Have students consider the fineness of the hair fibers, when attaching the Velcro. Students may want to use smaller strips between fibers. Allow time for students to construct, sketch and play with models. Use guided questions to facilitate in-group discussions. Have students sketch images of models on a dry erase board. Each model should be labeled and the polymeric structure identified. Facilitate the board meeting, using the guided questions as discussion prompts. Possible guided questions: How does structure effect movement? Why do some structures appear rigid? Which structure shows the least rigidity? How does structure affect various properties of hair – comb ability, brushing, curls, tangles, bounce, etc? Which model shows the greatest integrity and why?
Activity 3: Mini lab – Building simple polymers
Students will build models for polymers, polyethylene and polystyrene. Working in teams of three persons, they will construct linear and branched, homopolymers and copolymers. Prepare polymer cards in advanced, showing the molecular structure for each model. Use a power point slide to cut and paste images for the polymer cards. Images can be obtained from an internet search. Encourage students to use the cards to guide them in this activity.
Mini lab – Building simple polymers.
Pairs or team of 3 persons.
Objective: Students will build simple models of polymers using gummy bears and marshmallows.
Create a data table with the following categories in their interactive journals
- Homopolymer
o subcategories: linear and branched
- Copolymers
o subcategories: blocked, random, graft
- Visual representation
Materials: gummy bears, marshmallows, pipe cleaners, long toothpicks, and polymer cards. Special note: needle and thread may be used to link the polymers together.
Procedure:
Building the homopolymers with monomers, ethene and styrene.
The monomer, ethene will be represented by gummy bears. The marshmallows with piper cleaner are used to represent the monomer, styrene
1. Students will gather materials to build linear models of polyethylene and polystyrene.
2. Cut a minimum of six pipe cleaners in half. Each half will be used to fashion the ring structure for styrene. Bend the pipe cleaner to form a loop and place the extend end into the marshmallow. This is the monomer, styrene.
3. Follow the structural sequence shown on the polymer cards to build models.
Building the copolymers, polyethylene and polystyrene.
4. Combine the polymers, polyethylene and polystyrene, randomly to form a random copolymer.
5. Rearrange this copolymer to form a block copolymer.
6. Rearrange the copolymer again to form a graft copolymer.
Possible Post activity Questions:
How do the properties of a copolymer differ from the properties of a homopolymer?
Why would synthetic hair be a copolymer?
Polystyrene is the polymer in Styrofoam and polyethylene is the polymer in plastic storage containers; as copolymers, what properties would they exhibit?
Debrief activity by eliciting comments in whole group discussion with students. Students' response to post lab questions should be recorded in the journal.
Activity 4 – Part A: Making polymers
Students will make two types of polymers – slime, and cornstarch plastic. Each of the polymers will be plated and tested. The slime polymer requires a 4% solution of polyvinyl alcohol be mixed with a 4% solution of borax. To make the needed concentration of polyvinyl alcohol, dissolve 40 grams of polyvinyl alcohol in 960 grams of hot water (80 oC). The borax or sodium borate solution is prepared by dissolving 4 grams of borax in 96 grams of water. Each of these solutions should be prepared at least a day in advance. To make the cornstarch plastic, no advanced preparation is needed.
Lab: Making polymers – Slime and Cornstarch
Teams of 3 persons
Objective: Students will
- make two different polymer solutions
- observe changes in properties of the two polymer
- test the chemical and mechanical properties of the two polymers
Create a data table with the following categories in their interactive journals
- Description of polymers
o subcategories: slime and cornstarch
- Observation of process
o Subcategories: before, during and after
- Visual representation of monomers
o Subcategories: before, during and after
- Distinguishing properties with subcategories – texture, strength, elasticity, compression
Materials: For cornstarch polymers – cornstarch, oil, plastic sandwich bag, water, paper cup, food coloring, and 100-250 ml beaker.
For slime polymer – 4% borax solution, 4% polyvinyl alcohol solution, wooden stick, sandwich bag, paper cup, food coloring, 150-250ml beaker.
Procedure:
Cornstarch polymer
1. Weigh 9.6 grams of cornstarch place in a beaker.
2. Add 20 ml of water to the beaker, along with 2 drops of corn oil ~ 0.5 ml.
3. (Optional) add 2 drops of food coloring to the mixture.
4. Stir until the contents of the beaker are well mixed.
5. Pour half of the mixture into a petri dish and the other half onto a second petri dish.
6. Cover each dish with plastic. Poke small holes in the plastic covering to vent the solution.
7. Place the plated petri dishes in the microwave for 10-20 seconds on high.
8. Remove the plated petri dishes after 10-20 seconds, uncover and allow them to stand undisturbed for 24 hrs.
9. Make a second batch of cornstarch plastic. Repeat steps 1-6. Place the plated petri dishes in the microwave for 20-30 seconds on high.
10. Remove the plated petri dishes after 20-30 seconds, uncover and allow them to stand undisturbed for a few minutes.
11. Use this sample cornstarch to test the mechanical properties of the polymer.
12. Compress and stretch the sample. Test the elasticity.
13. Record all observation, questions, and comments in the journal
Slime Polymer
1. Measure 100 ml – 4% polyvinyl alcohol and place in a 250 ml beaker.
2. Slowly stirring the solution add 10 ml – 4% borax to the polyvinyl alcohol.
3. Place about one third of this solution onto a petri dish. To another petri dish, add a similar amount. Allow the plates to stand undisturbed for 24 hrs.
4. Using the remaining slime to test for compression, elasticity, strength, etc.
5. Record all observation, questions, and comments in the journal.
Possible Post activity Questions: How do the two polymers differ? Describe the cornstarch plastic upon heating? What physical changes occurred? How does adding oil to the cornstarch affect the properties of the plastic? How did the properties of the polyvinyl alcohol change when the borax was added? How would adding more borax affect the properties of the slime?
The slime activity was adapted from: http://chemistry.about.com/od/chemistryactivities/ss/slimerecipe.htm
The cornstarch lab adapted from: http://www.scienceoffcenter.org/science/310-corn-starch-plastic
Activity 4- Part B
In this activity, students test the effects of solvents on the polymers, as well as record the effect of temperature on the properties of the polymers. Students will note the time it takes for the polymer to degrade or deform.
Lab: Testing polymers – Slime and Cornstarch
Teams of three persons
Objective: Students will
- examine two different polymers after 24 hrs
- observe changes in properties of the two polymer
- test the chemical and mechanical properties of the two polymers
Create a data table with the following categories in their interactive journals
- Description of polymers – after 24 hrs
o subcategories: slime and cornstarch
- Observation of processes
o Subcategories: acid, acetone, base, boiling water, cold water, room temperature water
- Visual representation of polymers
o Subcategories: before, during and after processes
- Distinguishing properties with subcategories – texture, strength, elasticity, compression
Materials: 0.0001 M HCl, 0.0001 M NaOH, commercial acetone, water, beakers, thermometers, tongs, scissors, digital balances, hotplates, stopwatch.
Procedure:
1. Record observations of the polymers after 24 hrs.
2. Cut each polymer into seven – ~ 0.098 to 0.1 gram samples. Record the mass.
3. Label four beakers: HCl, NaOH, acetone, and water.
4. Add 100 ml of each solvent to a beaker, accordingly.
5. Heat the beaker fill with water to 100 o C.
6. Obtain two more beakers – add 100 ml of tap water to one and 100 ml of ice water to another.
7. To each beaker, add approximately 0.1 gram of cornstarch. Record the time.
8. Watch for the sample cornstarch to degrade or deform. Record the time it takes for the sample to degrade.
9. Repeat steps 3-8, for the slime sample.
Possible Post activity Questions: How do the two polymers differ after 24 hrs? What changes have occurred in the structure of these polymers? What do you notice about the solutions when the polymers dissolved? How does the relative strengths of the polymers compare? How can the degradation rate be determined for each polymer given the condition?
Debrief the activity with a board meeting, using the guided questions as discussion prompts.
Activity 5: Testing synthetic hair fibers
This is the culminating activity. Be confident that students can work independently to meet the objective. They are the scientists. Student may require assistance setting up equipment or mounting the hair sample. Provide each group a sample of synthetic hair. No group will share the same type of hair. The teams will test the three strands of hair for deformation or degradation in different solvents – acetone, water, acid solution, base solution, oil, and hydrogen peroxide. Have students test for elasticity, tensile strength, comb ability, curl resilience, and heat resistance. Students will write a formal lab report for this culminating activity. Assist the students in connecting the content to the activity. Guide them to use their journal when writing their reports. Providing students a rubric may help them with the report.
Lab: Testing synthetic hair fibers
Cooperative groups of three persons
Objective: Students will
- test the chemical and mechanical properties of synthetic hair fibers
- work independently to design the experiment and write the procedure
- write a formal lab report
Create a data table. Possible categories may include:
- Description of hair fibers
- Observation of processes
o Subcategories: acid, acetone, base, boiling water, oil, peroxide
- Visual representation of hair fibers
o Subcategories: before, during and after processes
- Distinguishing properties with subcategories – elasticity, tensile strength, comb ability, curl resilience, and heat resistance.
Materials: 0.0001 M HCl, 0.0001 M NaOH, commercial acetone, water, 30% hydrogen peroxide, ring stands, clamps, cross bar, Velcro, beakers, thermometers, tongs, scissors, digital balances, hotplates, stopwatch.
Comments: