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In is extremely important to differentiate between the terms 'intermolecular'
and 'intramolecular'. Intermolecular means from one molecule to another.
When intermolecular forces are overcome the molecules separate from
one another. This happens when a liquid boils, for example. The molecules
themselves remain integral and unaffected. The only thing that happens
is that they cease to be attached to one another.
Intramolecular forces hold the molecule itself together;
these are normally called chemical bonds, although there are cases of
hydrogen bonding from one part of a molecule to another part of the
same molecule.
Structure 2.2.8 - The nature of the force that exists between molecules is determined by the size and polarity of the molecules.
- Intermolecular forces include London (dispersion), dipole-induced dipole, dipole–dipole and hydrogen bonding.
- Deduce the types of intermolecular force present from the structural features of covalent molecules.
Guidance
- The term “van der Waals forces” should be used as an inclusive term to include dipole–dipole, dipole induced dipole, and London (dispersion) forces.
- Hydrogen bonds occur when hydrogen, being covalently bonded to an electronegative atom, has an attractive interaction on a neighbouring electronegative atom.
Tools and links
- Structure 1.5 - To what extent can intermolecular forces explain the deviation of real gases from ideal behaviour?
- Nature of science, Structure 1.1, Structure 2.1, Structure 2.3 - How do the terms “bonds” and “forces” compare?
- Nature of science - How can advances in technology lead to changes in scientific definitions, e.g. the updated International Union of Pure and Applied Chemistry (IUPAC) definition of the hydrogen bond?
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