Intermolecular Forces

Vapor Pressure and IF

• The stronger the intermolecular forces of the compound, the higher the boiling point of the compound because it will take more energy to break the bonds.

• It therefore follows that the stronger the intermolecular forces, the less volatile the compound will be, which means that its vapor pressure will be low.

Vapor Pressure

• Compounds with high vapor pressure want to turn to gas or vapor. Compound with low VP don’t want to convert to vapor easily unless more energy is added.

• Therefore compounds with LOW VP have High Boiling Points because their intermolecular forces are stronger) and compounds with HIGH VP have LOW Boiling points (because their intermolecular forces are weaker).

Summary

• Strong Intermolecular forces High Boiling Points compounds have LOW VAPOR PRESSURE and are LESS VOLATILE (don’t evaporate easily)

• Weak Intermolecular forces LOW Boiling Points compounds have HIGH VAPOR PRESSURE and are MORE VOLATILE (evaporate easily)