Why are Intermolecular Forces Important?

Intermolecular forces play a role in determining the physical properties of a substance (e.g.- melting point & solubility).

Types of Intermolecular Forces (Strongest to Weakest)

I. H-bonds

Found in polar substances where

H is bonded to O, N, or F.

Importance of H-Bonds

DNA replication &

protein synthesis.

Transpiration-Cohesion Theory

Respirators

Density of Ice < Density of Water

II. Dipole-Dipole forces

Found in polar substances where H is NOT bonded to O, N, or F.

III. London forces

Found in ALL molecular substances.

London forces become stronger as molecular size increases.Therefore, candle wax (C25H52) is a solid even though it is nonpolar & only has London forces.

The Effect of Intermolecular Forces on the Boiling Point of Molecular Compounds