Chemical CellsOxford AQA IGCSE Chemistry: Revision notes

A chemical cell (commonly called a battery, although strictly a battery is two or more cells connected together) is a device that transfers chemical energy into electrical energy.

• A simple chemical cell consists of two different electrodes placed in an electrolyte
• A chemical reaction between the electrodes and the electrolyte causes electrons to flow through an external circuit, producing a potential difference (voltage)

Inside a chemical cell, a chemical reaction takes place at each electrode:

• At one electrode, a reaction releases electrons (oxidation)
• At the other electrode, a reaction uses up electrons (reduction)
• This flow of electrons through the external circuit is the electric current, and the cell produces a potential difference that can be measured across its terminals

A chemical cell produces a potential difference only until the reactants are used up.

• As the chemicals inside the cell react, they are gradually consumed
• Once one of the reactants is fully used up, the chemical reaction can no longer continue, so the cell can no longer produce a current or maintain its voltage
• This is why batteries eventually 'run flat'

• Non-rechargeable cells: once the reactants are used up, the chemical reaction cannot be reversed, so the cell cannot be reused (e.g. many single-use household batteries)
• Rechargeable cells: the chemical reactions can be reversed by passing an electric current through the cell in the opposite direction, regenerating the original reactants so the cell can be reused many times (e.g. rechargeable batteries in phones)