Program Module #2: Polymers

Program Module #2: Polymers (Day 1 of 4)

 

[Note that the quizzes provided are named based on the material they cover, and NOT on the day that they are given.  I.e. The quiz labeled “Quiz – Electronics (day 1)” is the quiz that asks about the material covered on day 1 of the electronics module, and is meant to be given on day 2 of the electronics module.]

 

Materials needed every day:

  1. Nametags
  2. Markers
  3. Scissors
  4. Tape
  5. Safety glasses
  6. Calculators 
  7. Student notebooks 

 
Materials Needed:
 
1.) Copies of quiz

2.) Copies of notebook templates

3.) Black and yellow tetrahedron models

4.) Nylon Demo

5.) Computers (3 or 4 towers, with internal workings exposed)

6.) Dried thin films of glue (PVAc) on glass slides

7.) A few mL of 2M HCl to etch glue films

8.) Wooden stir sticks


 
Lesson Plan:
Objectives:

  • Outline the section and explain how/where polymers are used in computers
  • Provide students with a solid understanding of the terms atom, molecule, and polymer.
  • Provide students with a limited understanding of chemical bonding as it relates to the sharing of electrons in a covalent bond.
  • Students will understand that polymers are repeating units.
  • Apply knowledge of polymers as repeating units in elementary math calculations.
  • Use models of molecules to understand the concept of cross-linking.


Agenda:
 
1.)    Big picture talk (5 min)
2.)    Administer quiz (10 min)

3.)    PC ‘autopsy’ activity (15 min)
4.)    Lithography demo (5 min)
5.)    Lecture – atoms, electrons, bonding, and molecules (20 min)

6.)    Work time for related lecture problems (15 min)
7.)    Lecture – polymerization/Demo – producing nylon (5 min)
8.)    Demo – linear polymers, cross-linking, and the differences between the two types of materials (15 min)
 
Additional Information about Agenda Items:
 
3.)    Students are asked to identify polymer components of the PC.  The most common answer is the insulation of the wiring.  Other answers to look for include:  Glues/adhesives, the casing itself, resist on the circuit boards, and the monitor screen.

4.)    To etch the PVAc, just use a wooden stir stick to put some drops of HCL on the film, and after 30 sec wipe HCL and etched PVAc away with paper towel. This allows you to make a mask (like a stencil) out of PVAc and this type of patterning of polymers is very important to making computer chips out of a silicon wafer.

5.)    Timing can be difficult for this lecture.  Some students have strong science backgrounds and already know most of this material, while others have had very few classes in the physical sciences and will be almost visibly struggling right off the bat.  Be as complete and concise as possible, and be prepared to provide 1:1 assistance to students who may require it. You may need to keep the class moving relatively fast and rely on 1-on-1 help from the grad student volunteers for some of the students with less background knowledge.  
7.)    Go quickly here.  Focus on identifying and drawing a monomer from a diagram of the polymer, or vice versa.
8.)    Modeling kits are typically used to demonstrate the flexibility of linear chains (~10 carbons long), and the relative stiffness of the same chains once they’ve been cross-linked together.  Another possible demo that has worked very well in the past is to have the students form human chains of 4-5 students each by joining hands.  No matter how tangled up, a linear chain of students can slowly work its way free.  Instructors can then “cross-link” the student chains by holding on (separately from the joined hands) to 2 students from different chains, which will result in dramatically reduced chain mobility.

 

Handouts and presentations:

1.)     Notebook pages - Polymers (day 1)

2.)     Quiz – Previous Module (day 4)

 

 

Program Module #2: Polymers (Day 2 of 4)

Materials needed every day:

  1. Nametags
  2. Markers
  3. Scissors
  4. Tape
  5. Safety glasses
  6. Calculators 
  7. Student notebooks 


Materials List:
1.)    Polyurethane foam kits
2.)    Elmer’s glue (~40 mL per pair of students)
3.)    Sodium borate solution (saturated solution of “borax” in water) (~40 mL per pair of students) 4.)    Newspapers (to serve as placemats)

5.)    Paper or plastic cups (10 per pair. 4 for making slime (1 borate solution cup and 3 glue cups) and 6 for     

         polyurethane foam (3 each for part A and part B volumes))
6.)    Wooden stirrers (minimum 2 per pair, one for each activity)

 
Pre-Class Preparations:
1.)    Make copies of quizzes, handouts
 
Lesson Plan:
Objectives:

1.)    Students will gain additional appreciation of how cross-linking affects the properties of polymers.
2.)    Students will gain an increased knowledge of monomers and how they interact to form polymers
3.)    Students will apply knowledge of the effects of crosslinking to evaluate the expected/observed   

         stiffnesses of their prepared materials (both foams and slimes)


 
Agenda:
1.)    Big picture talk (5 min)

2.)    Administer quiz (10 min)
3.)    Make foams (20 min)
4.)    Make slimes (30 min)

5.)    Evaluate materials, and discuss findings related to crosslinking (25 min)
6.)    Distribute “careers in science” articles (5 min)
 
Additional Information about the Agenda Items:

1.)    The different PU foam kits we’ve used show a relatively wide range of reactivity.  Some mixtures, stirred just three times and allowed to sit for a few minutes, will overflow the paper cups in which they are mixed.  Others display hardly any volume change, despite vigorous stirring for several minutes.  Some pre-experimentation before the activity is given to the students is highly recommended to establish the optimal mixing protocol to produce the desired effects.  Additionally, the foams are hazardous to skin contact until they are completely dry (no longer tacky or sticky to the touch).  30 minutes is usually sufficient for most samples, but be careful about allowing the students to handle the foam directly.

In our experience, the polyurethane components don’t keep very well (may begin to self-polymerize within a year). So aim to order a new kit before the experiment and use it all within a relatively short amount of time.

2.)    Speedy, vigorous, and thorough mixing are important points with this experiment.  If you are too slow, or too gentle, cross-linking will occur at a large enough extent to make mixing difficult.  This will exclude some of the borax solution from the reaction, leading to anomalous results.

3.) The scientists featured in the “careers in science” handout are Cesar Garza, a photolithography engineer who includes a schematic of the lithography process in his interview. The other scientist is Stephanie L Kwolek, the inventor of Kevlar and she introduced the nylon rope demonstration in a 1959 Journal of Chemical Education article.

 

Handouts and presentations:

1.)     Handout - Careers in Science - Polymers (day 2)

2.)     Notebook pages - Polymers (day 2)

3.)     Quiz - Polymers (day 1)


 
Program Module #2: Polymers (Day 3 of 4)

 

Materials needed every day:

  1. Nametags
  2. Markers
  3. Scissors
  4. Tape
  5. Safety glasses
  6. Calculators 
  7. Student notebooks 

 
Materials Needed:

1.)    Cubes or strips of PVC and nylon (1 set per pair of students)
2.)    Saturated KBr and NaCl solutions of known densities

3.)    2 to 4 crystallizing dishes for KBr and NaCl solution float/sink tests

4.)    Tongs (2-4 pairs)

5.)    Graduated cylinders (one per pair of students)

6.)    Pop-bottle diver demo
7.)    Rulers or calipers (1 per pair of students)
8.)    Balances

9.)    Samples of PET and PVC for flame tests

10.)  ‘Shrinky Dinks’ sheets

11.)  Colored pencils or markers (The pencils work better)

12.)  Grocery bag (to serve as an oven liner)

13.)  Oven – preheated to 160 C (325 F)

  
Pre-Class Preparations:
1.)    Prepare copies of handouts and quiz for the day.
 
Lesson Plan:
Objectives:

1.)    Provide students with a review of density and density calculations
2.)    Provide demos that illustrate the concept of density as it relates to both liquids and solids.
3.)    Have students apply density calculations to the identification of unknown objects whose density is

         known.
4.)    Students will learn how to collect data related to the mass and volume of objects.
5.)    Students will observe the effects of temperature on polymers.
 
Agenda:
1.)    Big picture talk (5 min)
2.)    Administer quiz (10 min)
3.)    Lecture – Density, measurements of density (10 min)
4.)    Work time for notebook activity #1 (15 min)

5.)    Lecture – lab prep (10 min)

6.)    Activity - Density measurements (30 min)

7.)    Activity - Prepare Shrinky Dinks
8.)    Demo – flame tests (5 min)
 
Additional Information about the Agenda Items:

1.)    A good talking point here is the fact that density is a relatively easy-to-measure property that differs between different polymers, which allow us to easily sort recyclable plastics.  The pop-bottle diver demo provides an excellent physical demonstration of the effects of density changes, and the validity of the float/sink tests.
2.)     Each group of students will have samples of two different polymers.  Each group will measure the mass of each sample.  Each group will use dimension measurements (using rulers and/or calipers) to calculate the volume. They will also determine the volume using volumetric displacement in the graduated cylinders. The samples should be large enough to create a measureable displacement but also must be able to fit into the cylinder.  Place all measurements in the student notebook.  Students will also use two beakers containing different density liquids to observe the behavior of their polymers and verify their density calculations.  Students should be able to identify the polymer samples from their collected data, and the table of literature values provided in the notebook pages. Students will likely have to decide which volume determination (dimension measurement or volumetric displacement) was more accurate. Volunteers should engage students in discussion about the pros and cons of each type of volume determination.

3.)    Make sure the students are drying the sample as thoroughly as possible after it is exposed to any of the test liquids to avoid cross contamination, or erroneous mass data.  This activity always seems to take much longer than expected.  Plan to be nudging the students along as quickly as possible.

4.)    Sheets of Shrinky Dink material are cut into ~4”x3” panels.  The students are free to draw anything that strikes their fancy on their section.  Completed panels will be placed onto the grocery bag, and placed in the oven.  Do this in batches of 6 or 8 panels at once to prevent the oven door from opening frequently enough to cool the oven.  After 3-5 minutes, the panels will have shrunk considerably.  Should any panels be curled or folded in on themselves, they can be gently pulled apart and flattened with a pair of tongs provided the panel is still warm.  Do this while the panel is still in the oven.  By the time the grocery bag has been removed from the oven, and placed on the counter, the panels are usually too rigid to easily reshape
5.)    Heat a length of copper wire, and touch the hot end to the polymer sample in question to melt a quantity of the polymer onto the wire.  Return the wire to the flame and observe any color changes in the flame.  PET and PVC have nearly the same density, but in the presence of copper, Cl in the PVC will create a sea green flame, while the flame test of the PET will show no change (typical orange/yellow flames).

 

Handouts and presentations:

1.)     Notebook pages - Polymers (day 3)

2.)     Quiz - Polymers (day 2)
  
 

Program Module #2: Polymers (Day 4 of 4)
 

Materials needed every day:

  1. Nametags
  2. Markers
  3. Scissors
  4. Tape
  5. Safety glasses
  6. Calculators 
  7. Student notebooks 


Materials Needed:


1.)    Happy/Sad balls (one pair per pair of students)

2.)    Graph Paper or prepared blank graphs (20-30 copies)

3.)    Dry ice in an appropriate insulated container

4.)    Ice

5.)    Salt

6.)    4 beakers (>=800 mL) or large crystallization dishes

7.)    2 hotplates

8.)    5 pairs of Tongs

9.)    Meter sticks (1 per pair of students)

10.)  Liquid nitrogen demo materials: Liquid nitrogen, cryogenic gloves, objects to shatter.

11.)  “Hammer a rubber nail through balsa wood with a banana” demo (also uses liquid nitrogen)

12.)   Atomic trampoline demo (ball bearings bouncing on polycrystalline vs amorphous metal surfaces)

13.)   Thermocouple to measure dry ice temperature

14.)  4 thermometers (-20 to 100 C range)
 
Pre-Class Preparations:


1.)    Make copies (15-20) of quizzes and graph paper for the day and the template for the day.
 
Lesson Plan:
Objectives:

1.)    Students will gain an appreciation of the properties of polymers.
2.)    Students will observe and collect data and conclude for themselves how temperature can affect the

         properties of polymers.
3.)    Provide the formula for the coefficient of restitution and have students calculate this value for a variety

         of situations.
4.)    Students will use a laboratory notebook to collect data from an experiment.
5.)    Students will analyze data from an experiment graphically and draw conclusions from their analysis. 
 
Agenda:
1.)    Big picture talk (5 min)

2.)    Administer quiz (10 min)
3.)    Demo - Liquid nitrogen and atomic trampoline (5 minutes)

4.)    Lecture – Coefficient of restitution, lab prep, atomic trampoline demo (10 min)

5.)    Activity - Coefficient of restitution (45 min)
6.)    Create an average graph on the board and discuss the significance of the data collected. (15 minutes)

 


Additional Information about the Agenda Items:
 


1.)     Be sure to provide some “theatrics” when performing the demos and allow the students to ask questions, encourage questions, and let the students examine, with safety, the product of each demo. For the “hammer a rubber nail through balsa wood with a banana” demo, it is important to have the banana in the liquid nitrogen for about 10 minutes so it is frozen all the way through. The atomic trampoline demo facilitates a class discussion of which surface to do the happy/sad ball experiments on (lab bench or floor).
2.)    Students will be working in pre-determined pairs for this experiment.  Each station must be set up well ahead of time and must be monitored closely by an adult.  The students are required to place their polymer balls in the desired temperature at each station for a specific amount of time.  Be sure consistent time is given to each station and be sure that students use consistent measuring technique when collecting data for the coefficient of restitution.  The atomic trampoline demo reinforces this point nicely by showing the students that the surface upon which the balls are bounced can strongly influence their results.  If students are having trouble measuring by eye, smart phones are capable of filming the bounces with high enough frame resolution to easily measure the peak height of the bounce.  If time is expected to be tight, each group can take measurements of a subset of the different temperatures rather than at every station.  As long as there are multiple measurements taken at each different temperature, the overall data still looks pretty good. A grad student volunteer should handle the happy/sad balls coming out of the dry ice and from the boiling water bath.
3.)    Place a chart on the board with the student pairs clearly labeled along with a data chart to place all the data that the students collected.  Students will be instructed to graph their own data using graph paper.  Adults must patrol the room very carefully to be sure that students place height on the y-axis and temperature on the x-axis.  (dependent vs. independent variable).  Adults must also monitor the students to be sure that spacing is even throughout the graph.  Providing prepared blank graphs, rather than blank graph paper will help to alleviate these concerns.
4.)    Once all data is collected and analyzed, have students draw conclusions and place those conclusions in their notebook.  Discuss specific student findings as a class discussion.

Handouts and presentations:

1.)     Notebook pages - Polymers (day 4)

2.)     Quiz - Polymers (day 3)