When electric current passes through certain liquids, it does not just heat them up — it can actually take one metal apart, atom by atom, and deposit it onto another object.
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Not every liquid conducts electricity the same way — it depends entirely on whether it contains free ions.
📌 Which liquids conduct?
Good conductors: salt solution, acids, and tap water (which has dissolved salts and minerals).
Poor conductors: distilled/pure water, and liquids like pure alcohol or kerosene — they lack free ions.
Test it with an LED circuit: if the liquid conducts, the LED lights up when the circuit passes through it.
Olympiad trap: pure/distilled water is actually a very POOR conductor. It is the dissolved salts and minerals in tap or sea water that make it conduct — the water itself barely does.
Electroplating uses the chemical effect of current to coat one metal with a thin layer of another — always for a specific, practical reason.
📊 Why we electroplate
| Example | Reason |
|---|---|
| Chromium plating on car bumpers/taps | Resists rusting and gives a shiny finish |
| Zinc plating on iron (galvanising) | Protects iron from rusting |
| Gold/silver plating on cheap jewellery | Gives the look of a precious metal at low cost |
| Tin plating on copper cooking vessels | Prevents copper reacting with acidic food |
How it works: the object to be plated is connected as the NEGATIVE electrode (cathode); the coating metal is the POSITIVE electrode (anode). Current through the solution moves metal ions from the anode onto the cathode.
Achievers questions often describe a simple circuit and ask you to predict what happens if one part changes.
✨ Circuit basics
Series circuit
one single path
If one bulb fuses, every bulb in the circuit goes out.
Parallel circuit
multiple paths
If one bulb fuses, the others keep glowing.
Pro tip: An LED lights up only when current actually flows, which is exactly why it is used as a quick test for whether a liquid conducts electricity — a dim or unlit LED means a poor conductor, not a "broken" experiment.
12 NSO-pattern questions on the chemical effects of electric current, including two Achievers-level questions.
