Molecular forces are the attractive or repulsive interactions between molecules. These forces play a crucial role in determining the physical properties of substances, such as boiling and melting points. The main types of molecular forces include hydrogen bonds, dipole-dipole interactions, and London dispersion forces. Hydrogen bonds occur when a hydrogen atom is attracted to a highly electronegative atom, like oxygen or nitrogen. Dipole-dipole interactions happen between polar molecules, while London dispersion forces are weak attractions present in all molecules, arising from temporary shifts in electron density. Understanding these forces helps explain how substances behave in different conditions.