Polymer

A polymer is a very large molecule, a macromolecule, built from many small repeating units joined to one another by covalent bonds. The small units are called monomers, and the chemical process that joins them is polymerisation. Malay: polimer · Chinese: 聚合物.

Because a polymer chain contains hundreds or thousands of atoms, its molecular mass is enormous compared with a simple molecule such as water or carbon dioxide. The strong covalent bonds running along the chain are what make many polymers hard, strong and long-lasting. The chain is not random: one small group of atoms, the repeating unit, appears over and over along its length, which is why a polymer can be written as a repeating unit inside brackets with the subscript n. Polymers fall into two groups the exam expects you to know. Natural polymers occur in living things, natural rubber, protein, starch, cellulose, silk and wool. Synthetic polymers are manufactured in industry, usually from petroleum, and include polythene, PVC, polystyrene, nylon and Teflon. Both groups are built on the same principle: small units joining into one long chain.

Example. Polythene is a polymer made when many ethene molecules, CH₂=CH₂, join by addition polymerisation. Thousands of ethene units link into one long saturated chain, and this single macromolecule is the plastic used for bags and bottles.

Confusion to avoid. Do not confuse the polymer with its monomer. The monomer is the small starting molecule that repeats; the polymer is the large product built from many of them. Ethene is the monomer, while polythene is the polymer. It is also wrong to call every large molecule a polymer, only those built from a repeated unit qualify.

The idea of a polymer opens the whole Form 5 Polymers chapter, connecting monomers, polymerisation, natural rubber and plastics, so getting this definition exactly right protects marks across every question type in SPM Chemistry.