A Van der Waals force between molecules is a relatively weak intermolecular attraction. All neighboring molecules in liquids and solids attract each other. The nature and strength of these interactions depends on the types atom groups or functional groups that comprise the molecules. Some molecules are polar and some have hydrogen bonds. These relatively strong intermolecular interactions require specific structural features. Polar interactions require a nonsymmetric arrangement of bonds with atoms of different electronegativity--polar bonds. Hydrogen bonding requires that one species have a hydrogen atom bonded to a highly electronegative atom such as fluorine, oxygen, or nitrogen. The other species must have a highly electronegative atom without a hydrogen atom bonded to it. However, all molecules interact with other molecules through Van der Waals interactions.

Van der Waals forces are the attractive forces of one transient dipole for another. A transient...