Science — AI-generated practice question

Electric current flows through a solution only when it contains free ions (charged particles) that can carry charge.

Distilled water is pure water with no dissolved salts or minerals. It does not contain any ions, so no current can flow through it — it does not conduct electricity.

Rainwater, however, dissolves gases from the atmosphere, especially carbon dioxide (CO₂), forming carbonic acid (H₂CO₃). This dissociates to produce ions (H⁺ and HCO₃⁻). It also contains dissolved salts and other impurities. These ions act as charge carriers, allowing electricity to be conducted.

Thus, the presence of ions in rainwater makes it a conductor, while the absence of ions in distilled water makes it a non-conductor.

Source: Chapter 2, Section 2.2; Chapter 11, Section 11.1

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• The key concept is ions as charge carriers — examiners expect you to explicitly state that distilled water lacks ions while rainwater has them due to dissolved CO₂/salts.
• Mention CO₂ dissolving to form carbonic acid (H₂CO₃) → dissociates into ions; this shows understanding beyond just "impurities."
• Do not write about covalent bonds of water extensively — that is off-topic here.
• For 3 marks, one line each for: (1) principle, (2) distilled water explanation, (3) rainwater explanation — is the ideal structure.