Edexcel GCSE Chemistry (1CH0) — Chemical Changes
Every time you recharge a mobile phone battery, you are relying on the invisible transfer of electrons. Electrolysis is an example of a redox process, meaning that two opposite chemical changes happen simultaneously: oxidation and reduction.
In the context of electrolysis, these processes are defined entirely by what happens to the electrons ():
You can easily remember this rule by using the standard mnemonic OIL RIG:
During electrolysis, a direct current (dc) power supply creates two electrodes with opposite electrical charges.
To easily recall the polarity of each electrode in an electrolysis cell, you can use the simple mnemonic PANIC:
Students often mix up where the reactions happen; remember that vowels go together (Oxidation at the Anode) and consonants go together (Reduction at the Cathode).
In Edexcel mark schemes, you must always explicitly include the phrase 'of electrons' after stating 'loss' or 'gain' to secure full marks for defining oxidation or reduction.
If you are asked to explain ion movement and discharge, a perfect answer must state the name/charge of the ion, which specific electrode it moves to, and the charge of that electrode.
Electrolysis
The process of decomposing an ionic compound using electrical energy from a direct current (dc) supply.
Redox
A reaction where both reduction and oxidation occur at the same time.
Oxidation
The loss of electrons by a substance.
Reduction
The gain of electrons by a substance.
Anode
The positive electrode in an electrolysis cell, where oxidation takes place.
Cathode
The negative electrode in an electrolysis cell, where reduction takes place.
Anion
A negatively charged ion that migrates towards the anode.
Cation
A positively charged ion that migrates towards the cathode.
Put your knowledge into practice — try past paper questions for Chemistry
Electrolysis
The process of decomposing an ionic compound using electrical energy from a direct current (dc) supply.
Redox
A reaction where both reduction and oxidation occur at the same time.
Oxidation
The loss of electrons by a substance.
Reduction
The gain of electrons by a substance.
Anode
The positive electrode in an electrolysis cell, where oxidation takes place.
Cathode
The negative electrode in an electrolysis cell, where reduction takes place.
Anion
A negatively charged ion that migrates towards the anode.
Cation
A positively charged ion that migrates towards the cathode.
