Final answer:
Intramolecular forces, such as covalent and ionic bonds, are strong forces that hold atoms together within a molecule. Intermolecular forces are weaker forces between molecules responsible for changing a material's physical state, like melting and boiling.
Step-by-step explanation:
Intramolecular forces are the chemical bonds that hold the atoms within a molecule together. These include covalent, ionic, and metallic bonds and are very strong compared to intermolecular forces. For instance, breaking the covalent bonds in water requires 927 kJ per mole.
On the other hand, intermolecular forces are the forces of attraction between molecules. These are generally weaker than intramolecular forces and include hydrogen bonds, dipole-dipole interactions, and London dispersion forces. These forces are responsible for physical state changes such as melting and boiling; for example, converting liquid water to water vapor requires only about 41 kJ per mole at 100°C.
While intermolecular forces are weaker, they are critical for the bulk properties of substances. For example, the intermolecular attractions in liquid HCl require only about 17 kJ per mole to overcome, significantly less than the energy needed to break its H-Cl covalent bond (around 430 kJ per mole).