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Leaving Cert Chemistry: Intermolecular forces

How often Intermolecular forces comes up on the Chemistry papers, every year it was asked, and questions to try.

HL Asked on 7 of the last 10 Higher Level papers, most recently in 2025. most years

OL Asked on 1 of the last 10 Ordinary Level papers, most recently in 2016.

June 2027 is the first exam on the new Chemistry course. These come from the 2016–2026 papers, so read them as a guide.

Intermolecular forces, Higher Level(7 marks)

Quick ones on Intermolecular forces.

(a)Why is ice less dense than liquid water?
  1. Ice molecules are lighter than water molecules
  2. Hydrogen bonds hold the molecules in an open lattice
  3. Ice always contains trapped air bubbles
(b)Why does water have a much higher boiling point than expected for its molecular mass?
  1. It is an ionic compound
  2. Its covalent bonds are unusually strong
  3. Hydrogen bonding between the molecules
(c)Hydrogen bonding occurs when hydrogen is bonded directly to?
  1. Nitrogen, oxygen or fluorine
  2. Chlorine, bromine or iodine
  3. Carbon, sulfur or phosphorus
Show the answers

(a) Hydrogen bonds hold the molecules in an open lattice

(b) Hydrogen bonding between the molecules

(c) Nitrogen, oxygen or fluorine

Your turn: Higher Level questions on Intermolecular forces.

Higher Level

Asked on 7 of the last 10 Higher Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2026Not asked
2025Q10(a)
2024Not asked
2023Q8
2022Not asked
2021Q8
2019Q8
2018Q8
2017Q4(g)
2016Q11(b)

Links open the State Examinations Commission’s paper for that year.

More Intermolecular forces questions

Intermolecular forces, 3 marks

Which of these isomers of C5H12 has the highest boiling point?

  1. 2-methylbutane
  2. 2,2-dimethylpropane
  3. Pentane
Show the answer

Pentane

Unbranched pentane molecules have the largest contact area, so their London dispersion forces are the strongest.

Ordinary Level

Asked on 1 of the last 10 Ordinary Level papers, most recently in 2016.

Every paper, year by year

YearWhere it came up
2026Not asked
2025Not asked
2024Not asked
2023Not asked
2022Not asked
2021Not asked
2019Not asked
2018Not asked
2017Not asked
2016Q10(c)

Links open the State Examinations Commission’s paper for that year.

More Intermolecular forces questions

Intermolecular forces, 2 marks

Attraction between polar molecules such as HCl?

  1. Ionic bonds
  2. Metallic bonds
  3. Dipole-dipole forces
Show the answer

Dipole-dipole forces

The partly positive end of one molecule attracts the partly negative end of the next.

Intermolecular forces, 2 marks

Compared with intermolecular forces, covalent bonds within molecules are?

  1. The same strength
  2. Much stronger
  3. Much weaker
Show the answer

Much stronger

Boiling a covalent liquid only overcomes the weak forces between molecules. The covalent bonds stay intact.

Intermolecular forces, 2 marks

Weak attractions between non-polar molecules, caused by temporary dipoles, are called?

  1. London dispersion forces
  2. Hydrogen bonds (H-bonds)
  3. Ionic bonds between ions
Show the answer

London dispersion forces

Electrons move about, so for an instant one side of a molecule is slightly negative. This attracts neighbouring molecules weakly.

Other Chemistry topics

All of Leaving Cert Chemistry