Chemical Effects of Electric Current

• Understand which liquids conduct electricity and why (presence of dissolved ions).
• Understand electroplating — depositing a thin layer of metal on another object using electricity.

1. Pure water is a poor conductor; water with dissolved salts, acids, or bases conducts electricity well because it contains free ions.
2. When current passes through a conducting liquid, chemical effects occur, such as gas bubbles forming at electrodes or colour changes.
3. Electroplating uses electric current to coat one metal with a thin layer of another (e.g., coating iron with zinc to prevent rusting — galvanisation).
4. A conducting liquid used in this process is called an electrolyte.

Why does a lemon (which contains acidic juice) allow a simple circuit with electrodes to light a small bulb, while distilled water does not?

Lemon juice contains ions (from citric acid) that allow current to flow.
Distilled water has very few free ions, so it barely conducts electricity.

• Assuming all liquids conduct electricity equally (pure water is actually a poor conductor).
• Confusing electroplating (coating with metal) with simple painting or dipping.
• Forgetting that gas bubble formation at electrodes is evidence of a chemical (not just physical) effect.

• Why does saltwater conduct electricity better than pure water?
• What is electroplating used for?

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