International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Which of the following best describes a monomer?

1. A small molecule that combines to form a polymer

2. A large molecule made up of repeating units

3. A catalyst that facilitates polymerization

4. A type of alkane used in cracking

The correct answer is: A small molecule that combines to form a polymer

A monomer is best described as a small molecule that can chemically bond with other monomers to form a larger, complex structure known as a polymer. This process of linking monomers together through chemical reactions is called polymerization. Monomers serve as the fundamental building blocks of polymers, and their repeated connection creates the long chains or networks characteristic of polymeric materials. In contrast, polymers are the large molecules made up of these repeated monomer units. Catalysts play a role in speeding up the polymerization reaction but are not themselves monomers. Similarly, alkanes and their association with processes like cracking do not relate to the definition of a monomer; instead, they refer to breaking down larger hydrocarbons into smaller ones. Thus, the description of a monomer as a small molecule that combines to form a polymer accurately captures its essential role in chemistry.