Overview:
Students will learn about polymers as they observe and describe examples of them in their own lives. They will then simulate a polymer by making a human chain, and figure out ways to modify the simulated polymer.

Science Background:
A polymer is any molecule that has many repeating units; "poly" means "many," and "mer" means "unit." If you think of a paperclip as a molecule, a polymer is like a long chain of paperclips. Polymers make up many of the things around us, and can be natural or synthetic. For example, all plastics are made of polymers. Other polymers include clothes; shoes; wood; erasers; and biological molecules such as proteins, DNA, and complex carbohydrates. Some examples of things that are not polymers are metal, water, and glass. A true polymer consists of at least 50 units, but some polymers have many more than 50 units.

Materials Needed:
Various examples of familiar polymers, such as:

• A plastic grocery bag
• A plastic cup
• A CD
• A styrofoam or plastic egg carton
• Paper
• Wooden pencil with eraser
• Crackers
• Disposable diaper
• Beef jerky
• Lambswool
• Yarn
• Leather
• Dog hair in a clear plastic bag

Part One: What Is A Polymer?
1. Place all of the polymers you have available on a table for the students to look at. Ask them to make a short list of which objects are similar and why, then another list of which objects differ from each other and why.
2. Ask the students to share their answers, and write some of these on the board.
3. Explain that all of the objects on the table have one thing in common – each is made of many repeating units so small that we can’t see them with our unaided eyes. Scientists call objects made of repeating units polymers, a word that means "many units." A polymer is like a chain of paperclips, where one paperclip is a "mer," or unit. Several paperclips linked together represent the polymer.
4. Ask students if they can find examples of polymers in the classroom, or on their clothes or shoes.
5. Point out to students that polymers are important in part because they can act in so many different ways. One way to illustrate this point is to show the students a plastic cup and plastic bag side by side. Ask them a series of questions, such as:
- If I drop this cup, what will happen?
- What will happen if I drop this bag?
- Which is easier to tear – the cup or the bag?
- It’s pretty hard to tear the cup, but it’s very easy to stretch the bag, right?
- I can drink out of the cup, but do you think it would be a good idea to try to drink out of the bag?
- Would you rather carry your groceries in the bag or the cup?

Part Two: How Can We Make A Polymer?
1. Tell the students that they are going to help you design polymers that can do different things.
2. Ask for six student volunteers, and have them come to the front of the class.
3. Have the students "form" a polymer and make modifications to it. You might lead them through a dialogue that goes something like this:
- OK, I need for you six to form a polymer. (Most likely, the students will either hold hands or link their elbows. If they don’t, suggest that they do so.)
- All right, now, very carefully, I want you to try to move around.
- Was it easier or harder for you to move as a polymer than it would be for you to move by yourself? What made it harder?
- Now, I need for the whole class to help me come up with some different ideas. How could we make it even more difficult for our polymer to move?
- (Shake a pair of students’ arms gently, and tell them that this is where they are "bonded.")
- The arms are the bond that our polymer has now. It’s kind of floppy. Do you think it is a weak or a strong bond?
- How could we change the bonds in our polymer to make it difficult for them to move? (If students don’t come up with these ideas on their own, suggest strategies such as crossing their legs or feet, locking their elbows, keeping their arms tight, and linking their ankles.)
- OK, now, let’s use some of these suggestions to make the polymer stronger.
- (After the class polymer has created its new, stronger bonds, have them try to move again.)
- Was it easier for you to move the first time or the second?
- Which polymer was more like a bag, and which was more like a cup?

Teaching Tip:
Depending on the age level of the students, it may be difficult to get males and females to hold hands.

For Some Hands-On Polymer Activities:
Please visit The Science House web site, www.science-house.org. Click on "Learning Materials" and find the "Countertop Chemistry" activities. Specific polymer activities listed include Oobleck, Gluep, and Clear Slime Polymer.

This is a publication of the National Science Foundation Science and Technology Center for Environmentally Responsible Solvents and Processes (CERSP), NSF Cooperative Agreement CHE-9876674. For more information about CERSP, please visit the web site, www.nsfstc.unc.edu.