Polymers have very large molecules. Each molecule is a long chain made of a very large number of atoms. Poly(ethene), used for plastic bags, is an example. The atoms in a polymer molecule are linked to other atoms by strong covalent bonds.
The forces between polymer molecules, the intermolecular forces, are relatively strong. This is because the molecules are so large. In small molecules such as methane, the intermolecular forces are weak, which is why those substances are usually gases or liquids. In polymers the stronger forces mean that a lot more energy is needed to separate the molecules, so most polymers are solids at room temperature.
You should be able to recognise a polymer from a diagram of its bonding and structure. Look for a very long chain of atoms joined by covalent bonds, often shown as a short repeating section with a bond leaving each end.
