What are some common mistakes students make with intermolecular forces?
Confusion between INTERMOLECULAR and INTRAMOLECULAR forces is common.
The INTRAMOLECULAR force is of course the interatomic force; usually a covalent bond; or it could be an ionic bond between discrete ions that extends throughout the entire lattice (here the structure is non-molecular).
The INTERMOLECULAR force is the force between molecules. In order of magnitude, these include (i) hydrogen-bonding (where hydrogen is bound to a strongly electronegative atom), (ii) dipole-dipole interactions, where molecular dipoles align, and (iii) dispersion forces.