What would happen with non-electrolytes?

2 marks · Hard

A student tries to electrolyse solid iodine and observes no current flows through the circuit. The student then dissolves the iodine in water and tries again, but the bulb still does not light. State and explain what these results show about the electrical properties and bonding type of iodine.

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Iodine does not conduct electricity, either as a solid or in solution, which shows it is a non-electrolyte and consists of covalent molecules.

Also accept: Iodine does not conduct electricity because it does not form ions; Iodine contains covalent bonds and does not ionise in water

Common mistakes: Saying iodine is ionic; Claiming iodine ionises in water

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Marking points

M1 · 1 mark · Identifies that iodine does not conduct electricity as a solid or in solution

A1 · 1 mark · Explains this is because iodine is a covalent non-electrolyte (i.e. does not ionise/contain ions)

Worked solution

Iodine does not conduct electricity as a solid or when dissolved in water, so it is a non-electrolyte.

This indicates it consists of covalent molecules and does not form ions needed for current flow.