Polymers are substances with very large molecules. A polymer molecule is a long chain of atoms, often made of the same small unit repeated again and again, such as the carbon and hydrogen atoms in poly(ethene). All the atoms in a polymer molecule are linked to other atoms by strong covalent bonds.
The intermolecular forces between polymer molecules are relatively strong. They are much stronger than the forces between small molecules, because the molecules are so large. As a result, more energy is needed to separate them, and polymers are solids at room temperature.
As with small molecules, it is the intermolecular forces that are overcome when a polymer softens or melts, not the strong covalent bonds along the chains. To recognise a polymer from a drawing of its bonding and structure, look for a very long chain of atoms joined by covalent bonds, with a unit that repeats along the chain.
