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Leaving Cert Physics & Chemistry: Crystals & intermolecular forces

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

HL Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

OL Asked on 8 of the last 9 Ordinary Level papers, most recently in 2025. most years

Crystals & intermolecular forces, Higher Level(7 marks)

Quick ones on Crystals & intermolecular forces.

(a)Why does water boil at 100 °C while H2S, a heavier molecule, is a gas at room temperature?
  1. Water is an ionic compound
  2. Hydrogen bonding between water molecules
  3. O–H bonds break on boiling but S–H bonds do not
(b)Diamond is an example of which type of crystal?
  1. Metallic (giant lattice)
  2. Molecular (simple covalent)
  3. Covalent macromolecular
(c)Diamond and graphite are allotropes of carbon. Allotropes are…
  1. Different physical forms of the same element
  2. Compounds with the same molecular formula
  3. Atoms of an element with different neutron numbers
Show the answers

(a) Hydrogen bonding between water molecules

(b) Covalent macromolecular

(c) Different physical forms of the same element

Your turn: Higher Level questions on Crystals & intermolecular forces.

Higher Level

Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q7(i), Q7(n)
2024Q12(d)
2023Q7(d), Q7(l)
2022Q7(f), Q12(c)
2021Q7(f), Q7(g), Q7(h)
2019Q12(b)
2018Q7(c), Q12(d)
2017Q7(e), Q12(c)
2016Q7(c), Q7(f)

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

More Crystals & intermolecular forces questions

Crystals & intermolecular forces, 2 marks

What type of crystal is ice?

  1. Ionic
  2. Covalent macromolecular
  3. Molecular
Show the answer

Molecular

Ice is made of separate H2O molecules held in place by hydrogen bonds. Within each molecule the bonds are covalent, but the crystal is molecular.

Crystals & intermolecular forces, 3 marks

Why do ionic crystals such as sodium chloride have high melting points?

  1. Their molecules are very large
  2. Strong forces between oppositely charged ions
  3. Only weak van der Waals forces hold them
Show the answer

Strong forces between oppositely charged ions

Every ion is held by strong electrostatic attraction to its neighbours. A lot of energy is needed to break up the lattice, so the melting point is high.

Crystals & intermolecular forces, 2 marks

In a metallic crystal, the positive metal ions are held together by…

  1. A sea of delocalised electrons
  2. Shared pairs between pairs of atoms
  3. Hydrogen bonds
Show the answer

A sea of delocalised electrons

Metal atoms release their outer electrons into a sea that moves through the lattice. Attraction between the ions and this sea is the metallic bond.

Ordinary Level

Asked on 8 of the last 9 Ordinary Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2025Q7(d), Q7(f)
2024Q7(e), Q7(g)
2023Q7(e), Q7(i), Q8
2022Q7(b), Q7(h), Q7(i)
2021Q7(e), Q7(h), Q8
2019Not asked
2018Q7(e), Q7(g)
2017Q7(d)
2016Q7(f), Q8

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

More Crystals & intermolecular forces questions

Crystals & intermolecular forces, 2 marks

Ice and iodine are examples of?

  1. Ionic crystals
  2. Metallic crystals
  3. Molecular crystals
Show the answer

Molecular crystals

Separate molecules are held in place by weak forces between them. So molecular crystals are soft and melt or sublime at low temperatures.

Crystals & intermolecular forces, 2 marks

Allotropes are?

  1. Compounds with the same formula
  2. Different forms of the same element
  3. Atoms with different numbers of neutrons
Show the answer

Different forms of the same element

Diamond and graphite are allotropes of carbon: same atoms, different arrangement. Atoms with different neutron numbers are isotopes.

Crystals & intermolecular forces, 3 marks

Why does water have a much higher boiling point than expected for its size?

  1. Hydrogen bonds between its molecules
  2. Ionic bonds between its molecules
  3. Its molecules are very heavy
Show the answer

Hydrogen bonds between its molecules

H bonded to O is strongly polar, so neighbouring molecules attract strongly. Extra energy is needed to pull them apart, so water boils at 100 °C.

Other Physics & Chemistry topics

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