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PLASTICS IN OUR LIVES
MASTER TEACHER Nancy Long
GRADES 6-8
OVERVIEW
This chemistry lesson presents the physical and chemical
properties of polymers to the middle-school student. Students will learn
what a polymer is and how polymers are produced. They will have hands-on
experience with the properties of various polymers. They will create a
cross-linked polymer in a lab investigation and compare its properties to those
of its components. They will examine the issue of how polymers have changed
our lives in the last 100 years. They will use the Internet to research
information about polymer production, usage, and disposal and will report their
findings to the class.
ITV SERIES
World of Chemistry #119 The Age of
Polymers
Land to Landfill #102 Food Packaging and the
Food System
LEARNING OBJECTIVES
The student will be able to
* identify the properties of polyethylene, polystyrene,
polyester, and polyamide
* name the uses of various polymers
* produce a cross-linked polymer and compare its properties to
the properties of its components
* explain the benefits of using polymers over some natural
materials
MATERIALS
(Pre-viewing activity)
1 empty plastic milk jug
1 nylon windbreaker
1 plastic food storage bowl
1 dry-cleaner clothes bag
1 nylon knee-high stocking
1 CD
1 football or basketball, not leather
1 meter of weedeater line or fishing line
(lab activity – per participant)
1 small plastic cup
1 spoon or stir stick
30 ml Elmer’s Glue-All
60 ml water
30 ml 20 Mule Team Borax
1 plastic recloseable sandwich bag
1 large beaker or Pyrex measuring bowl (one for the whole group)
PRE-VIEWING ACTIVITY
Assemble the milk jug, windbreaker, knee-high stocking, food
storage bowl, dry-cleaner bag, CD, ball, and weedeater or fishing line in view
of the class. Ask students to describe each item by answering these
questions: Is it flexible? Is it transparent? Is it hard? Ask
students to predict how all of the items are alike.
FOCUS FOR VIEWING
To give students a specific responsibility for viewing, ask them
to watch to find out how all of our displayed objects are alike and what other
items fall into the same category.
VIEWING ACTIVITIES
START the World of Chemistry #119 The Age of Polymers video
at the picture of the toy train. The sound of the train whistle is heard. PAUSE
the tape at the picture of the scientist looking out of the laboratory window.
The words, The Age of Polymers, appear on the screen. The narrator has
just said, “We live in an age of polymers.” Ask students, “What are
all of our items made of?” (Polymers) “What else did you see that can be
made of polymers?” (Toys, automobile parts, clothing, food wrap, artificial
ice for skating, artificial turf for sports, dishes, artificial heart) RESUME
the video. PAUSE when the scientist is running his hand over the side of
the red car door. Ask students, “ How did the test show that polymers
make car doors better?” (The door was not dented by the wrecking ball.)
Focus students’ viewing by asking, “What do you think polymers, or plastics,
are made of?” Call on students to respond. Say, “Let’s watch to find
out if our answers were correct.” RESUME the video. PAUSE
it when the two green ovals appear on top and bottom of the carbon atoms.
The narrator has just said, “Ethylene’s ability to form polymers comes from
the double bond between the carbon atoms.” Call on a student to come to
the screen and label the carbon atoms with a washable overhead transparency
marker. Call on another student to label the hydrogen atoms. Call on
another student to label the double bonds between the carbon atoms. Ask
the class if the labels are correct. Thank the participating students. RESUME
the video. PAUSE when the two polymer chains touch and the reaction
stops. The narrator has just said, “The reaction ends when two polymer
chains link up.” Ask, “What are polymer chains made of?”
(monomers) “What causes them to link up?” (Free radicals, molecules
with unpaired electrons) Focus students’ viewing by saying,
“Let’s watch to learn about the most widely-used polymer, polyethylene.”
RESUME the video. STOP when the hand reaches to pick up the green
soft-drink bottle. The narrator has just said, “Soft-drink bottle caps
are made of cross-linked polyethylene.” Ask, “What does
cross-linking do to a polymer?” (Cross-linking makes it tougher and stronger.)
Say, “We are going to make another kind of cross-linked polymer.”
ACTIVITY
Give each student a small plastic cup. Have each measure
30 ml of 20 Mule Team Borax into the cup and pour in 30 ml of water. Wait
about two minutes for the borax to become saturated. While waiting, explain that
20 Mule Team Borax, a laundry additive, is sodium tetraborate. Ask,
“What are the properties of the dry sodium tetraborate?” (It is granular or
powdery). Pour off the water, leaving the wet borax in the bottom of the cup.
Ask, “What are the properties of the wet sodium tetraborate?” (It is
grainy.) In a large beaker or Pyrex measuring bowl, mix 30 ml of
Elmer’s Glue-All per participant with an equal amount of water and stir until
it is thoroughly combined. While stirring, say, “Elmer’s Glue-All is
polyvinyl alcohol. What are the properties of polyvinyl alcohol? (It is
viscous, sticky, and wet.) Say, “We are mixing it with water.
Water is a chemical too. What are the properties of water?” (It is a clear,
colorless liquid.)
Give each student a spoon or stir stick. Pour an amount of
the glue-water mixture equal to the amount of borax into each person’s cup and
have them stir until the contents of the cup become solid (a few seconds).
Have students remove the new substance from the cup and experiment with its
properties. Ask, “What is our cross-linked polymer like?” (It is solid
when compressed, but liquid when allowed to rest; it is dry and cold; it forms
bubbles when resting; it is stretchy when pulled slowly, but brittle when pulled
quickly.) Ask, “Are the properties of the new substance like those of
the borax? (No) Like the Elmer’s glue? (No) Like the water? (No). Say,
“The chemical change that occurred when the molecules of the sodium
tetraborate combined with the H20 and the polyvinyl alcohol changed both the
physical properties and the chemical properties of the substances.” Take
up the cups and spoons and provide each student with a sandwich bag to hold the
new polymer.
RESUME the video. STOP when the worker
throws the large piece of polystyrene on top of the stack. The narrator
has just said, “It’s bulky, but light-weight and easy to work with.”
Ask, “ How is polystyrene different from polyethylene?” (It is stiffer and
more brittle. Expanded polystyrene is very light in weight and makes excellent
packing material.)
EJECT the tape. Say, “ One of the most common
ways we use plastics is in food packaging. How is that good?” (It keeps
food fresher; it is cheaper to produce; It makes it easier to transport food to
stores and to our homes.) Say, “How was food packaged before we had
plastics?” (It was in glass bottles, metal cans, or paper cartons or
wrapping.) Ask, “Have you ever wondered how food was packaged in pioneer days?
Let’s watch to see what one group of kids learned about food packaging then
and now.” INSERT THE TAPE Land to Landfill #102,
Food Packaging and the Food System. START the tape where the three young
people are walking down the path. The girl is saying, “ I guess we need
SOME sort of packaging to hold food in.” STOP the tape when the rat is
seen running behind the barrel. The girl has just said, “I just saw a
rat.” Ask, “What did the students learn about the production of
food packaging?” (It uses up natural resources and energy.) Ask, “What
did they learn about food packaging in 1830?” (There wasn’t much food
packaging. Most people grew their own food. The General Store had bulk
foods in barrels, which was not very sanitary.)
POST-VIEWING ACTIVITIES
Say, “Now that we know something about how polymers are made
and used, let’s extend our knowledge base by doing some research on the
Internet.” Give each student a copy of the research questions on
plastics. Explain that they will have two class periods to complete the
assignment, and they may work with a partner. Students may also work on
the assignment at home, in the classroom after school, or at the public library.
ACTION PLAN
Conduct an experiment to see which polymer is strongest without
breaking. Use strips of plastic cut from food packaging and organized by
recycling code number. Calculate the density of each polymer and analyze
the data to see if there is a correlation between density and strength.
Participate in a neighborhood effort to increase awareness of
the need to recycle plastic containers and grocery bags.
Work with a group to decide which polymer is best for
packaging various products. Students must select a product to be sent
through the mail from the following list: an egg, a set of photographs, a bottle
of dye, a banana, or a small radio. They must decide what kind of
protection the item needs and what polymer is best suited to pack the item for
mailing. They must then report to the class which packaging they chose and why
they chose it, based on the properties of the polymer.
Visit a local petrochemical company to see how polymers are
made.
EXTENSIONS
Language arts
Write a story about a student who invents a new kind of polymer
with amazing properties.
History
Create a time line showing the development of synthetic
materials through history.
Art
Create a sculpture using recycles plastic items. Use as
many different kinds of plastic as you can.
Math Calculate the density of various polymers using the
formula Density = mass/volume.
Research the weight of plastic grocery bags vs. paper grocery
bags, the amount of weight each will hold without breaking, and the amount of
storage space needed for 1000 of each kind of bag. Graph your results.
Use the Internet to find out the tonnage of recycled plastic for
this town over the last year. Calculate to see how much plastic is
recycled per capita.
Physical Education
Conduct an inventory of sports equipment in this school to see
how many items are made of polymers and how many are not. Determine the
percent of sporting goods on hand that are made of polymers.
Interview a coach to find out what he or she thinks are the
advantages and disadvantages of sporting goods made of polymers.
Career Investigations
Find out about careers in petrochemicals and polymer production.
Plastics in Our Lives
Objective: Use the Internet to get information about polymers
and their uses.
Instruction: You have two class periods to complete this
assignment. You may work with one partner. You may work on the
assignment at home, after school in the classroom, or at the public library.
Part 1: Go to http://www.plasticsresource.com
Find the answers to the questions below in the
Glossary/FAQ pages of that website.
1. What is plastic made of?
2. What kind of plastic is used for:
soft drink bottles?
bottles for household chemicals?
meat packaging film?
bottle caps?
egg cartons?
3. Why do car manufacturers use plastic parts?
4. Give an example of how plastics can help save energy.
5. How much plastic is recycled?
Part 2: At the beginning of the Glossary/FAQ page of
this website, on the left side of the page, the letters of the alphabet are
listed. Some letters are circled. This is the glossary. Click
on the circled letters to find the entries listed below. Choose one of the
terms and prepare a two-minute report on it for the class. Include a
sample or a visual of the process or concept.
Blow-molding
Cogeneration
Extrusion
Pelletizing
Source reduction
Stabilizers
Waste-to-energy
Updated: April 01, 2008
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