How do intermolecular forces affect physical properties?

Intermolecular forces play a crucial role in determining various physical properties of substances. In particular, they significantly influence viscosity and boiling points. Viscosity is a measure of a liquid's resistance to flow, and it is directly related to the strength of intermolecular attractions. Stronger intermolecular forces result in higher viscosity, as molecules are more strongly attracted to one another, making it harder for them to move past each other.

Similarly, boiling point reflects the energy required to overcome these intermolecular forces. A substance with stronger intermolecular attractions will have a higher boiling point because more energy (in the form of heat) is needed to separate the molecules from each other and allow them to transition from the liquid phase to the gaseous phase. Therefore, the strength and type of intermolecular forces present—whether they are hydrogen bonds, dipole-dipole interactions, or London dispersion forces—can significantly impact both the viscosity and boiling point of a substance.