The terms “intermolecular interaction” and “intermolecular force” are sometimes used interchangeably. However, it is important to distinguish the force from the potential energy of interaction. In classical mechanics, the strength of the force, F, is related to the distance dependence of the potential energy, E_p, by F = –dE_p/dr. How does the intermolecular force depend on separation for a typical intermolecular interaction that varies as 1/r⁶?