You can easily imagine a chemical polymer as a very long metal chain. Each individual link in this imaginary chain represents a single chemical monomer. A polymer might contain thousands or even millions of these repeating chemical links.
The physical properties of a polymer depend entirely on its monomer composition and chain length. They also depend on how those long chains fold and tangle with one another. Some connected chains form rigid plastics, while other chains form stretchy and flexible rubber.
These massive polymer molecules exist abundantly in both the natural world and human industry. Natural polymers include the protein in your muscles, the cellulose in plants, and your own DNA. Synthetic polymers are human-made materials created originally in chemical laboratories.
These include things like nylon fabrics, styrofoam cups, and PVC plumbing pipes. The chemical process of connecting monomers is called polymerization. Addition polymerization successfully joins molecules directly together without losing any of the original atoms.
Condensation polymerization joins molecules but forces them to eject a tiny byproduct like water. Students often struggle to realize that a single plastic water bottle is a polymer. It is essentially one massive, interconnected network of repeating chemical chains.