Grade 12 Chemistry Unit 4 : Polymers

This unit, “Polymers,” examines the giant molecules that make up much of the material world — from plastic bags and nylon ropes to your own skin, hair, and the starch in injera. You will explore what polymers are, how small monomer molecules join to build them, the two chemical routes of polymerization, and how chemists classify polymers by structure, origin, and response to heat.

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Chapter 4.1 – Introduction to Polymers

This chapter introduces the giant chainlike molecules and their building blocks.

• Definitions: Define a polymer as a large molecule built from many repeating units, and a monomer as the small building-block molecule that links to form it.
• Size of Polymers: Explain the degree of polymerization (DP) and how it determines a polymer’s molar mass.
• Identifying Polymers: Recognize materials with a polymeric nature and distinguish true polymers from shorter oligomers.

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Chapter 4.2 – Polymerization Reactions

This chapter explains the two chemical processes that turn monomers into polymers.

• Polymerization Basics: Describe a polymerization reaction and explain why monomers must have two or more functional groups.
• Addition Polymerization: Explain chain-growth polymerization of unsaturated monomers such as ethylene and styrene, including the three steps — chain initiation, chain propagation, and chain termination.
• Condensation Polymerization: Explain step-growth polymerization and the release of a small molecule such as water, producing polymers like nylon 66, Dacron (polyester), and Bakelite.
• Calculations: Calculate the number of monomer units using n = molar mass of polymer ÷ molar mass of monomer.

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Chapter 4.3 – Classification of Polymers

This chapter covers the different ways chemists organize polymers into useful groups.

• By Monomer Type: Classify polymers as homopolymers (one monomer) or copolymers (two or more monomers), including random and regular copolymers.
• By Origin: Distinguish natural polymers — carbohydrates, proteins, cellulose, natural rubber, and DNA — from human-made synthetic polymers.
• Structures and Uses: Draw the structures of polyethylene, polypropylene, PVC, Teflon (PTFE), and PMMA, and relate their properties to their everyday uses.
• By Response to Heat: Classify polymers as thermoplastics (melt and can be recycled) or thermosets (cross-linked, cannot be remolded).

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Learning Outcomes

By the end of this unit, you will be able to:

• Define polymer, monomer, and degree of polymerization, and recognize polymers in everyday materials.
• Distinguish addition from condensation polymerization and describe the steps of each process.
• Write a polymerization reaction from given monomers and predict the monomer from a given polymer structure.
• Classify polymers by monomer type, origin, formation reaction, and response to heat.
• Relate the structure of plastics, rubbers, carbohydrates, and proteins to their properties and uses.