Explain why ionic compounds have high melting points.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Ionic compounds contain oppositely charged ions, giving rise to strong electrostatic forces of attraction between the ions. These forces act in all directions because the ions form a three‑dimensional giant lattice. A large amount of energy is therefore required to overcome these forces and separate the ions, resulting in high melting points.
Examiner tips
- Use the exact terms: "oppositely charged ions", "electrostatic forces of attraction", "three‑dimensional lattice", "large amount of energy".
- Show the logical sequence: ions → forces → lattice → energy required → high melting point.
- Keep the answer concise – 4 marks, so one sentence per point.
- Avoid unnecessary words or repetition.
Common mistakes
- Using vague terms such as "strong bonds" instead of "electrostatic forces of attraction".
- Failing to mention the three‑dimensional lattice structure.
- Writing a long paragraph instead of clear, separate points.
Mark scheme (4 marks)
- Ionic compounds contain oppositely charged ions / positive and negative ions
- There are strong electrostatic forces of attraction between the oppositely charged ions
- These forces act in all / every direction (because the structure is three-dimensional / a giant lattice)
- A large amount of energy is needed to overcome these forces / to separate the ions
Key terms in this question
Related
- All AQA GCSE Chemistry (8462) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →