Intermolecular forces exist between particles because all particles, whether they are atoms, molecules, or ions, have electric charges. These charges can create attractive or repulsive forces between particles, depending on their relative positions and charges. Intermolecular forces are responsible for many of the physical properties of matter, such as boiling point, melting point, viscosity, and surface tension. They play a crucial role in determining the behavior of liquids and solids, and they are essential to many chemical reactions and biological processes.