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Edexcel International A Level Chemistry

Topic 7
Intermolecular Forces

Intermolecular forces decide whether a substance is a gas, a liquid or a solid, why ice floats, why alcohols boil far above alkanes of the same size and what will dissolve in what. This topic covers London forces, permanent dipole-dipole interactions and hydrogen bonding, the anomalous properties of water, boiling temperature trends and the choice of solvents, all examined in Unit 2.

Exam Unit
Unit 2
WCH12/01 – IAS
Specification Points
7.1 – 7.6
6 points, 17 sub-points
Sub-topics
6 pages
Revision notes available
Exam Board
Edexcel IAL
Pearson International

Revision Notes

Induced dipoles
London
Forces
instantaneous dipole, induced dipole
1

London Forces

How moving electrons create instantaneous and induced dipoles, and why electrons and shape decide their strength.

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Polar molecules
Permanent
Dipoles
δ+ ··· δ− attraction
2

Permanent Dipole-Dipole Forces

Which molecules have a permanent dipole, how polar molecules attract, and a routine for unfamiliar molecules.

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N-H, O-H, H-F
Hydrogen
Bonding
lone pair to δ+ hydrogen
3

Hydrogen Bonding

The requirement, the four-feature exam diagram, water, ammonia and hydrogen fluoride, and predicting other cases.

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Ice, boiling, surface
Anomalous
Water
open lattice, high boiling temperature
4

Anomalous Properties of Water

Why water boils at 100 °C, why ice floats and why water has a high surface tension.

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Alkanes, alcohols, HX
Boiling
Trends
chain length, branching, HF to HI
5

Boiling Temperature Trends

Alkane chain length and branching, alcohols against alkanes, and the hydrogen halides explained by forces.

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Like dissolves like
Choosing
Solvents
hydration, hydrogen bonds, hexane
6

Choosing Solvents

Hydration of ions, alcohols in water, why halogenoalkanes do not dissolve, and non-aqueous solvents.

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Summary maps

Download, print and revise the key facts of this topic at a glance.

Summary map · PDF

Intermolecular Forces Map

Edexcel International A Level Chemistry · Unit 2 · Topic 7A Intermolecular Forces

The whole section on one A4 page: bonds or forces, London forces, permanent dipoles, hydrogen bonds, H₂O, NH₃ and HF, and why water is odd.

Download the map6 key ideas + a data table · A4 portrait · print ready
Summary map · PDF

Boiling Temperatures and Solvents Map

Edexcel International A Level Chemistry · Unit 2 · Topic 7B Physical Properties

The whole section on one A4 page: chain length, branching, alcohols against alkanes, the hydrogen halides, water as a solvent and other solvents.

Download the map6 key ideas + a data table · A4 portrait · print ready

© 2026 Online Learning System. For personal study: printing is allowed; editing, copying and redistribution are not.

Specification Coverage

Topic 7 Intermolecular Forces – Edexcel International A Level Chemistry

The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 7.

7.1
understand the nature of the following intermolecular forces:
i
London forces (instantaneous dipole-induced dipole)
ii
permanent dipole-permanent dipole interactions
iii
hydrogen bonds
7.2
understand the interactions that give rise to hydrogen bonding in:
a
H₂O
b
liquid NH₃
c
liquid HF
7.3
understand the following anomalous properties of water resulting from hydrogen bonding:
i
its high melting and boiling temperature when compared with similar molecules
ii
the density of ice compared to that of water
7.4
be able to predict the presence of hydrogen bonding in molecules analogous to those mentioned in 7.2
7.5
understand, in terms of intermolecular forces, physical properties shown by substances, including:
i
the trends in boiling temperatures of alkanes with increasing chain length
ii
the effect of branching in the carbon chain on the boiling temperatures of alkanes
iii
the relatively low volatility (higher boiling temperatures) of alcohols compared to alkanes with a similar number of electrons
iv
the trends in boiling temperatures of the hydrogen halides HF to HI
7.6
understand factors that influence the choice of solvents, including:
i
water, to dissolve some ionic compounds, in terms of the hydration of the ions
ii
water, to dissolve simple alcohols, in terms of hydrogen bonding
iii
water, as a poor solvent for compounds (to include polar molecules such as halogenoalkane), in terms of inability to form hydrogen bonds
iv
non-aqueous solvents, for compounds that have similar intermolecular forces to those in the solvent
Specification Coverage

Topic 7 Intermolecular Forces – Edexcel International A Level Chemistry

The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 7.

7.1
understand the nature of the following intermolecular forces:
i
London forces (instantaneous dipole-induced dipole)
ii
permanent dipole-permanent dipole interactions
iii
hydrogen bonds
7.2
understand the interactions that give rise to hydrogen bonding in:
a
H₂O
b
liquid NH₃
c
liquid HF
7.3
understand the following anomalous properties of water resulting from hydrogen bonding:
i
its high melting and boiling temperature when compared with similar molecules
ii
the density of ice compared to that of water
7.4
be able to predict the presence of hydrogen bonding in molecules analogous to those mentioned in 7.2
7.5
understand, in terms of intermolecular forces, physical properties shown by substances, including:
i
the trends in boiling temperatures of alkanes with increasing chain length
ii
the effect of branching in the carbon chain on the boiling temperatures of alkanes
iii
the relatively low volatility (higher boiling temperatures) of alcohols compared to alkanes with a similar number of electrons
iv
the trends in boiling temperatures of the hydrogen halides HF to HI
7.6
understand factors that influence the choice of solvents, including:
i
water, to dissolve some ionic compounds, in terms of the hydration of the ions
ii
water, to dissolve simple alcohols, in terms of hydrogen bonding
iii
water, as a poor solvent for compounds (to include polar molecules such as halogenoalkane), in terms of inability to form hydrogen bonds
iv
non-aqueous solvents, for compounds that have similar intermolecular forces to those in the solvent