What would happen with non-electrolytes?
3 marks · NormalWater is often used as the solvent in electrolysis experiments. Pure water conducts electricity only very weakly, but when a small amount of sodium chloride is added, it conducts electricity much better.
Explain why pure water is a poor conductor of electricity and why adding sodium chloride increases the conductivity so much.
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Pure water has very few ions, so it cannot carry much current. Adding sodium chloride provides many ions (Na+ and Cl⁻), which carry charge and allow electricity to flow more easily.
Also accept: Pure water does not have enough ions to conduct electricity. Sodium chloride dissolves to give ions that can move and carry current.
Common mistakes: Claiming pure water conducts well; Not mentioning ions
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Marking points
B1 · 1 mark · States that pure water has very few ions.
B2 · 1 mark · Mentions inability to conduct electricity (very weak conductor).
B3 · 1 mark · Explains that sodium chloride adds ions (Na+ and Cl-) so conductivity increases significantly.
Worked solution
Pure water is a poor conductor because it contains very few ions, so there are not enough carriers for electric current. When sodium chloride is added, it dissolves to provide Na⁺ and Cl⁻ ions, greatly increasing the number of charge carriers and the solution's conductivity.