A geologist is testing a crystal from a rock sample. The crystal melts at 1750 ∘C1750\,^\circ\text{C}1750∘C. Neither the solid crystal nor the molten crystal conducts electricity.
Which explanation best accounts for both results?
It is made of small molecules with weak forces between them, and it has no charged particles free to move.
It is a giant lattice of atoms joined by strong covalent bonds, and it has no charged particles free to move.
It is a giant lattice of oppositely charged ions held by strong attractions, and the ions are free to move when molten.
It is a giant structure of positive metal ions held by strong bonding, and it has delocalised electrons free to move.
84 exam-style questions on AQA GCSE Chemistry 2.2 How bonding and structure are related to the properties of substances, covering 2.2.1a The three states of matter, 2.2.1b Limitations of the simple particle model, 2.2.2 State symbols in chemical equations, 2.2.3 Properties of ionic compounds, 2.2.4 Properties of small molecules, 2.2.5 Polymers, 2.2.6 Giant covalent structures, 2.2.7 Properties of metals and alloys, and 2.2.8 Metals as conductors. Each one has a worked solution and a mark scheme showing where the marks go.