A student is designing an electrical tilt sensor to operate in a high-temperature industrial furnace. They test the electrical conductivity of magnesium chloride (MgCl2\text{MgCl}_2MgCl2) in two different physical states: as a solid at 25∘C25^\circ\text{C}25∘C and as a molten liquid at 720∘C720^\circ\text{C}720∘C.
Explain, in terms of structure and bonding, why solid magnesium chloride is a non-conductor, whereas molten magnesium chloride conducts electricity extremely well.
59 exam-style questions on Edexcel GCSE Chemistry 2.5 Types of substance, covering 2.5.1 Classifying substances by structure and bonding, 2.5.2 Properties of ionic and simple molecular substances, 2.5.3 Giant covalent structures: diamond and graphite, 2.5.4 Fullerenes, graphene and simple polymers, 2.5.5 Properties of metals and non-metals, and 2.5.6 Limitations of bonding models and representations. Each one has a worked solution and a mark scheme showing where the marks go.