Cells and batteries
A cell contains chemicals that react to produce electricity
A simple cell is two different metals in contact with an
electrolyte
The voltage depends on the type of electrodes and the
electrolyte
The bigger the difference in reactivity between the two metals,
the bigger the voltage
Two electrodes of the same metal give zero volts
A battery is two or more cells in series , giving a greater
voltage
In a non-rechargeable cell the reaction stops when a reactant is
used up . Alkaline batteries are non-rechargeable
A rechargeable cell can be recharged because the reaction is
reversed when an external current is supplied
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A simple cell electrolyte — a salt solution zinc copper the more reactive metal V − + voltmeter — reads the potential difference The more reactive metal is always the negative electrode. The bigger the difference in reactivity between the two metals, the bigger the voltage. The zinc loses electrons and they flow through the wire to the copper, so a current flows. A non-rechargeable cell stops working when one of the reactants is used up. A simple cell: zinc and copper strips dipping into an electrolyte in a beaker, connected through a voltmeter, with the voltmeter reading and the more reactive metal labelled as the negative electrode
Reading a table of cell voltages: the further apart two metals are in the
reactivity series, the larger the voltage. A negative voltage means
the metals are the other way round. Order metals by the algebraic
value, not the size of the number
An electrochemical cell produces electricity from a reaction. An
electrolytic cell uses electricity to cause a reaction. A plan for a
cell investigation that includes a power supply has confused the two, and
is limited to the lowest level
A cell investigation needs the same two metals every time when
another variable is being tested, and the volume (not "amount") of
electrolyte stated
The rest of this topic is in the full Exam Guide The complete AQA GCSE Chemistry guide — every topic, exam checklist and common mistake — is coming soon. Until then, the first topic in every unit is free to read.
In the full topic
• Cells and batteries• Fuel cellsRead the free chemistry topics →