A sample of potassium chloride, an ionic compound, is dissolved in water. The solution conducts electricity. After the water evaporates, the dry crystalline potassium chloride residue does not conduct electricity.
Why does the dried residue fail to conduct electricity?
The ions are held in fixed positions and cannot move through the solid to carry charge
The water molecules carried the charge in the solution and are now absent
The ions have changed into neutral atoms as the water evaporated
The positive and negative ions move in opposite directions, so their charges cancel
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.