Monomer is defined as which of the following?

• A. A long chain molecule formed from many small molecules
• B. A small molecule unit that makes up a polymer
• C. A polymer's repeating unit
• D. A mixture of monomers

Answer: (B)

Monomers are the small molecules that can join with others to form polymers. They are the building blocks from which polymers are made, linking together to create long chain molecules. The repeating units inside a polymer come from these monomer units, so a monomer is the basic unit that makes up the polymer’s structure. That’s why the best description is a small molecule unit that makes up a polymer. The other ideas describe the polymer as a whole, or the repeating unit inside the polymer, or a mixture of molecules, none of which capture what a monomer fundamentally is.