Intermolecular forces
High School
Definition
The attractive forces that act between molecules, rather than within them. These forces, which include hydrogen bonding and van der Waals forces, are weaker than chemical bonds but determine properties such as boiling point, melting point, and solubility.
Worked examples
Water \((\)H\(_2\)O\()\) has strong hydrogen bonding between molecules, giving it a boiling point of \(100\,^\circ\)C\(\).
The hydrogen bonds are intermolecular forces that require significant energy to break during boiling.
Methane \((\)CH\(_4)\) has only weak van der Waals forces, so it boils at \(-162\,^\circ\)C\(\).
Weaker intermolecular forces mean less energy is needed to separate the molecules into gas.
Ethanol dissolves in water because both form hydrogen bonds, but hexane does not.
Similar intermolecular forces between substances allow them to mix and dissolve.
Common mistakes
- Intermolecular forces and covalent bonds are the same thing → Intermolecular forces act between molecules; covalent bonds hold atoms together within a molecule Intermolecular forces are much weaker and break during phase changes, while covalent bonds do not.
- Stronger intermolecular forces mean lower boiling points → Stronger intermolecular forces mean higher boiling points More energy is required to overcome stronger attractions and separate the molecules into gas.
- All intermolecular forces are hydrogen bonds → Intermolecular forces include hydrogen bonding, dipole-dipole, and van der Waals forces Hydrogen bonding is just one type; many molecules have only weaker van der Waals interactions.
Where you'll use it next
You'll apply intermolecular forces when predicting physical properties in organic chemistry, understanding solutions and solubility, studying phase diagrams, and exploring biochemistry topics like protein folding and DNA structure.
Found in 1 StudyPug lesson
Understanding Intermolecular Forces: The Invisible Bonds
11th Grade11thChemistry 11
Dive into the world of intermolecular forces! Learn how these subtle attractions shape physical properties, influence molecular arrangements, and form the foundation of advanced chemistry concepts.
See also
Covalent bondingIonic bondingMolecular geometryStates of MatterProperties of LiquidsProperties of Solids
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026