The electrical conductivity of ionic substances
2 marks · EasyA student says that ‘solid lead(II) bromide contains charged particles, so it should conduct electricity’. Explain, giving a calculation or statement, why this is incorrect.
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Solid lead(II) bromide does not conduct electricity because its ions are held in fixed positions and cannot move to carry charge.
Also accept: Although lead(II) bromide has ions, in the solid state they are not free to move.; The solid contains ions but they cannot move, so it does not conduct electricity.
Common mistakes: Referring to electrons moving; not explaining movement.
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Marking points
M1 · 1 mark · Recognises that ions are present in the solid.
A1 · 1 mark · Explains that ions are not free to move in the solid, so it does not conduct electricity.
Worked solution
Solid lead(II) bromide contains ions, but in the solid state these ions are fixed in the lattice structure and cannot move. Because they cannot move to carry charge, the solid does not conduct electricity.