Intermolecular Forces and Properties
Compare London dispersion forces, permanent dipole interactions and hydrogen bonding to explain boiling, volatility and solubility.
How to study Higher Chemistry
Move deliberately between structure, equations, quantitative models, unfamiliar evidence and justified experimental conclusions, while using current official materials for exact paper and assignment practice.
Core concepts
Concept 1
London dispersion forces act between all atoms and molecules and generally strengthen as electron clouds and molecular contact increase.
Exam cue: Name all relevant intermolecular forces and compare their overall strength.
Concept 2
Permanent dipole–permanent dipole attractions act between polar molecules; hydrogen bonding is a particularly strong intermolecular attraction.
Exam cue: Connect stronger intermolecular attraction to more energy required for separation.
Concept 3
Relative intermolecular attractions between solute and solvent help predict whether substances mix or dissolve.
Exam cue: For solubility, compare polarity and possible hydrogen bonding in both substances.
Risk pitfalls and guardrails
Claiming that non-polar molecules have no intermolecular forces.
Guardrail: Check structures, formulae, charges, equation balance, units, signs and experimental conditions before committing to the final conclusion.
Calling every attraction involving hydrogen a hydrogen bond.
Guardrail: Check structures, formulae, charges, equation balance, units, signs and experimental conditions before committing to the final conclusion.
Explaining solubility only with the phrase like dissolves like.
Guardrail: Check structures, formulae, charges, equation balance, units, signs and experimental conditions before committing to the final conclusion.
Memory anchors
London dispersion forces
Temporary uneven electron distribution induces attractions between neighbouring particles.
Permanent dipoles
Polar molecules attract through oppositely charged ends.
Hydrogen bonding
A strong attraction involving hydrogen bonded to a highly electronegative atom and a suitable lone pair.
Stronger attractions
Stronger intermolecular forces usually raise boiling point and lower volatility.
Larger molecules
More electrons and greater contact can strengthen London dispersion forces.
Solubility clue
Dissolving is favoured when solute–solvent attractions can replace the attractions being disrupted.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
Which intermolecular force acts between every atom and molecule?
What causes a London dispersion force?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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