Methane (CH₄) is a simple molecular substance. Explain why methane is a gas at room temperature and does not conduct electricity in any state.

Cambridge International IGCSE Chemistry (0620) — 2.5 Simple molecules and covalent bonds · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Methane has weak London dispersion forces between its molecules.

Because the forces are weak, only a small amount of energy is required to overcome them, giving methane a low boiling point; hence it is a gas at room temperature.

Methane molecules have no net charge – they are neutral.

There are no free electrons or ions present, so there are no mobile charge carriers to conduct electricity in any state.

Examiner tips

  • Mention weak London dispersion forces and low boiling point to justify gas state. State that methane is neutral and lacks free charge carriers to explain non-conductivity.
  • Use clear, concise sentences and include all four key points to secure full marks.

Common mistakes

  • Confusing covalent bonds with ionic bonds and claiming methane conducts electricity. Omitting the fact that methane has no free electrons or ions. Using vague terms like "molecules are far apart" without linking to weak forces.

Mark scheme (4 marks)

  1. Methane has weak intermolecular forces between molecules
  2. Little energy is needed to overcome these intermolecular forces, so methane has a low boiling point and is a gas at room temperature
  3. Methane molecules have no overall charge / are not charged particles
  4. There are no free electrons or ions to carry charge / no mobile charge carriers in any state

Key terms in this question

simple molecular substance · conduct electricity

Related

More Simple molecules and covalent bonds questions

▶ Try answering this question with AI marking (free) →