Intermolecular Forces and States of Matter

Intermolecular Forces and States of Matter:
Intermolecular Binding Forces
Collision diameter
The distance between molecules at which the attractive and repulsive forces just balance each other
The most stable distance
van der Waals Forces
Keesom forces : Dipole-dipole.
(water, hydrochloric acid, alcohol, phenol)
Debye forces : Dipole-induced dipole.
(ethylacetate, methylene chloride, ether)
London forces : Induced dipole-induced dipole.
(carbon disulfide, carbon tetrachloride, hexane)
Molecules – Attractions & Repulsions

Dipole-dipole attractions occur over
longer distances than induced dipole
attractions, so they take place among
larger groups of molecules.
The opposite partial charges attract one another, while the like partial charges
repel one another.
Molecules will tend to move so as
to maximize attractions and minimize repulsions
Hydrogen Bonds
a special type of dipole-dipole attraction (exceptionally short and polar)
small size and large electrostatic field of Hydrogen atom
Change materials properties : boiling point, dielectric constant,
three dimensional array of inter- or intra- molecular structures
Please for more details see Physical Pharmacy, Martin