Intermolecular Forces
The comparatively weak attractions acting between separate molecules rather than within them.
Unit
kJ/mol
In depth
Typically one to ten per cent as strong as covalent bonds, these forces determine melting and boiling points, viscosity, surface tension and solubility, while the covalent bonds inside molecules stay intact through such changes. Their strength grows with molecular size, polarity and hydrogen-bonding capacity.
Examples in the real world
Boiling water breaks hydrogen bonds between molecules but leaves every O–H bond untouched.