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Major Concepts

Major Concepts. Activity 19 Plastics are a part of a group of chemicals known as polymers, which are made of repeating molecules (called monomers) linked together. The chemical structure of a polymer affects their physical properties

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Major Concepts

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  1. Major Concepts Activity 19 • Plastics are a part of a group of chemicals known as polymers, which are made of repeating molecules (called monomers) linked together. • The chemical structure of a polymer affects their physical properties • Substances react chemically in characteristic ways with other substances to produce substances with different chemical properties

  2. Activity 20 Title: Modeling Polymers

  3. Models help scientists investigate the characteristics of systems. • When might it be helpful to work with a model? • Architectural models: how a building will look • Computer models of processes that are not easily observed (digestion). • The model may not look like the object. • It must function like the process. • A model can use physical objects, a simple diagram, or a mathematical equation.

  4. What represents the: Atom Molecule Nucleus Protons Neutrons Electrons Bonds We need to use a simpler model: To represent the structure of even a small polymer would require thousands of units linked together. This large number necessitates the use of a model. Vinyl Alcohol Molecular Model

  5. Read pg. B-42 Problem: How can you use models to represent changes that occur during a chemical reaction? Hypothesis/Initial Thoughts:

  6. Paper Clip Model • Each individual paper clip represents a monomer (one molecule). • You will compare the behavior of the model monomer to that of a model polymer and a model cross-linked polymer. • Compare what you observe in this activity with your observations in the last activity.

  7. In this activity you will: • Pour, Stir, and Pull • Monomers (Single Paper Clips) • Polymers (A Chain of Paper Clips) • Cross-Linked Polymers (Diagram in Book) • Paper Clip Chain: Polymerization Model • Chemical bonds formed between monomers. • Polyvinyl Alcohol Model from last class

  8. E Procedure: Follow the procedure on pages B-43 to B-45 Data/Observation: Comparing Model Monomers and Polymers

  9. What did you notice? • Pouring and Stirring become increasingly difficult because the cross-linked polymer bunches together and moves as a single unit. • When the polymers are Pulled out of the cup, they tend to lift out as a chain or as a bunch.

  10. How do you think you could make your model polymer even more solid? • Create more bonds. • We will now create another kind of model of polymers. • A pair of students holding both hands will represent a double-bonded vinyl alcohol monomer. • Put your backpacks under the table.

  11. With the person next to you… • Hold both hands and then start to walk around the room. You are a monomer. • Now, form a bond with two more monomers (you should be a chain of 6 people) and walk around the room. You are a polymer. • Cross-link the polymers chains. Walk around the room.

  12. What effect did going from monomers to polymers have on your ability to move? • Traveling in a monomer pair was much easier than as a polymer. • The polymer chain is still fairly flexible. • Cross-linked: the longer and more complex the chain, the slower the progress. • Cross-linked PVA.

  13. Analysis Question #3 • Transparency 20.1 “Cross-Linking a Polymer” • What is the difference? • Student Sheet 20.2, “Polymers in Daily Life.” • Circle the polymers you have seen or used in the past week.

  14. Monomer Other models How could you show a polymer with this model? How could you model a cross-linked polymer?

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