Intermolecular Forces

Potassium nitrate is attracted to itself by two forces: London Dispersion and dipole-dipole.

Dipole-dipole is the attraction between two polar molecules.  Polar molecules have a slightly positive end and a slightly negative end.  When the molecules are oriented correctly, the opposite charges attract and create moderately strong bonds.

London Dispersion is the weakest intermolecular force.  It occurs in the brief moment when the electrons in a molecule are at a position to form a temporary dipole-dipole bond.  This happens when electrons are not distributed evenly around the nucleus.  This bond only happens for a fraction of a fraction of a second and is gone as soon as it happens, making it very weak.