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Teacher Notes

Teacher Background and Directions: Students need to start bringing in empty plastic containers for this activity. Allow them at least a week to collect. They need to be aware of the code embossed on most plastic containers. Their goal is to obtain one container for each numbered code. Stress that these containers need to be clean and dry and will not be returned.

Teacher Overview of the Activity: As containers are collected, students will become aware of the different types of plastics. They will notice the codes on the plastics and begin to wonder what they mean and how one distinguishes one type of plastic from another.

Teacher Demonstration: Before the engagement activity it is important to define polymer and plastic. You can demonstrate the long length of a polymer by purchasing strings of plastic beads in any color (available at novelty, Arts and Crafts and party stores). Cut each strand once then attach them into a long chain with transparent tape. One bead represents the monomer, the repeating unit, of the polymer molecule. Another analogy is to string paperclips together in a long chain. In HOP Jr, found on the ACC website, has a good modeling activity, “Create Your Own Polymer” that might be appropriate for fifth and sixth graders.

Plastics are polymers. A polymer molecule can be hundreds to thousands of units long. The parent chain is composed of carbon atoms and hydrogen atoms are attached to the carbon chain for the plastic called polyethylene. There is high density polyethylene and low density polyethylene but both are made out of carbon and hydrogen. The low density polyethylene has branches of carbon and hydrogen coming off of the parent carbon chain. See the diagram below for the parent chain of polyethylene:

For further information, read the background information for teachers and provide students with the student edition.

Preparation: Group the containers that the students have collected, by recycled code. Using scissors, remove the code from each container in the group. Set up a key so that you know which letter of the alphabet corresponds to each recycled code. For a two liter bottle: letters A, E, Z, and M might be assigned for PETE. Cut the containers into large sections. For example: a two liter bottle could be cut in four or five pieces. Label all the pieces with letters from the alphabet according to your key. Each group of students shall receive a gallon baggie filled with about ten plastic pieces. Students work in groups of three to five students to fill in their data table.

Evaluation: Students’ charts should be completed during this activity. Conversing with each student group will give the teacher a sense of the students’ prior knowledge and the questions they are beginning to have as they manipulate the plastics. Remember the Engage Phase does not involve direct teaching. It is important not to help students classify the containers, because it defeats the purpose of the Learning Cycle. Remember students are classifying according to observed physical properties. They will not necessarily be able to group them according to the recycling codes. This activity does not have specific answers. Students are often frustrated because they cannot group them to their satisfaction. This shows the necessity of more testing and provides a reason for doing the next activity.

A class discussion could evolve around the placement of plastic pieces on a chalkboard or bulletin board according to their groupings. A nice class visual representation would involve placing small self-adhesive hook and loop fastener strips on the outside of the plastic container pieces. These then could be placed on hook and loop fastener strips located on a bulletin board.

NOTE: Recycling is not available in all areas. Check your local community recycling organization.

For more information on the recycle codes go to: http://plastics.americanchemistry.com/Plastic-Resin-Codes.

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Student Activity Sheet

Engage #2: Can You Classify Plastic Containers?

Student Activity Sheet Name: ________________________

Your Mission: Use their physical properties to classify the containers. Using all of your senses (except taste), examine each container for texture, gloss or shine, color, flexibility, transparency, odor, etc. You may have as many groups as necessary. Fill in the chart below.

Purpose: To group plastic containers according to their physical properties.

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