Chemical Cells (Oxford AQA IGCSE Chemistry)
Revision Note
Written by: Alexandra Brennan
Reviewed by: Stewart Hird
Chemical Cells
A chemical cell is a source of electrical energy
The simplest design consists of two electrodes made from metals of different reactivity immersed in an electrolyte and connected to an external voltmeter by wire, creating a complete circuit
A common example is zinc and copper:
Zinc is the more reactive metal and forms ions more easily, readily releasing electrons
The electrons give the more reactive electrode a negative charge and sets up a charge difference between the electrodes
The electrons then flow around the circuit to the copper electrode which is now the more positive electrode
The difference in the ability of the electrodes to release electrons causes a voltage to be produced
The greater the difference in the metals reactivity then the greater the potential difference produced
The electrolyte used also affects the voltage as different ions react with the electrodes in different ways
In some chemical cells, the potential difference is only produced until the reactants are used up
Diagram of a simple cell
Examiner Tips and Tricks
The reactivity series of metals can be used to compare different cells and determine which combination would produce the greatest voltage.
Don't get this type of cell confused with an electrolytic cell. An electrolytic cell uses electrical energy to break up an ionic compound whereas a chemical cell uses a chemical reaction to generate electricity.
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