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Edexcel GCSE Chemistry · 1CH0
Edexcel 1CH0 · 3.23 Check the specification (PDF) (opens in a new tab)
Electrolysis is a process in which electrical energy from a decomposes an . To decompose a substance means to split it chemically into simpler substances.
The electrolyte is the material being broken down. It is an ionic compound that is either molten or dissolved in water. In these liquid states, its ions can move; this is necessary for the liquid to conduct electricity and for electrolysis to take place.
A d.c. power supply provides the electrical energy that drives the decomposition. Direct current travels in one direction, maintaining two connections with opposite polarities. These connections lead to electrodes placed in the electrolyte, completing the circuit through the conducting liquid.
When the supply is switched on, electrical energy is transferred to the electrolyte and chemical changes occur. The electrolyte is therefore a reactant being decomposed, rather than simply a liquid through which current happens to pass.
A d.c. supply provides the electrical energy that decomposes an electrolyte. The electrodes make electrical contact with the conducting liquid.
A description of electrolysis should connect four ideas:
The detailed movement of positive and negative ions, and the substances formed at each electrode, depend on the electrolyte and are considered separately. The central idea here is the energy-driven decomposition: electrolysis uses electrical energy to bring about a chemical change.
Electrolysis is the decomposition of an electrolyte using electrical energy from a direct current supply.
Ionic compound molten or dissolved in water → mobile ions → conducting electrolyte → d.c. electrical energy supplied → electrolyte decomposed.
Include all three essential ideas in a definition of electrolysis: an electrolyte is decomposed, electrical energy is supplied, and the supply is direct current (d.c.).
Do not describe electrolysis merely as ‘passing electricity through a liquid’. State that the liquid is an electrolyte and that it is decomposed.
Do not confuse the process with the substance: electrolysis is the process; the electrolyte is the molten or dissolved ionic compound being decomposed.
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Electrolysis
The decomposition of an electrolyte using electrical energy from a direct current supply.
Electrolyte
An ionic compound that is molten or dissolved in water, so its ions are able to move.
Direct current (d.c.)
An electric current that flows in one direction.
Decomposition
The chemical splitting of a compound into simpler substances.
Put your knowledge into practice — try past paper questions for Chemistry
Electrolysis
The decomposition of an electrolyte using electrical energy from a direct current supply.
Electrolyte
An ionic compound that is molten or dissolved in water, so its ions are able to move.
Direct current (d.c.)
An electric current that flows in one direction.
Decomposition
The chemical splitting of a compound into simpler substances.