Electrolysis (Edexcel GCSE Combined Science) : Revision Note

Stewart Hird

Last updated

Electrolysis

  • When an electric current is passed through a molten or aqueous ionic compound the compound decomposes or breaks down

  • Liquids and solutions that are able to conduct electricity are called electrolytes

  • Covalent compounds cannot conduct electricity hence they do not undergo electrolysis

  • An electrolytic cell is the name given to the set-up used in electrolysis and which consists of the following:

    • Electrode: a rod of metal or graphite through which an electric current flows into or out of an electrolyte

    • Electrolyte: ionic compound in molten or dissolved solution that conducts the electricity

    • Anode: the positive electrode of an electrolysis cell

    • Anion: negatively charged ion which is attracted to the anode

    • Cathode: the negative electrode of an electrolysis cell

    • Cation: positively charged ion which is attracted to the cathode

Transfer of Charge, IGCSE & GCSE Chemistry revision notes

Diagram showing the direction of movement of electrons and ions in the electrolysis of NaCl

  • During electrolysis the electrons move from the power supply towards the cathode

  • Electron flow in electrochemistry thus occurs in alphabetical order as electrons flow from the anode to the cathode

  • Positive ions within the electrolyte migrate towards the negatively charged electrode which is the cathode

  • Negative ions within the electrolyte migrate towards the positively charged electrode which is the anode

Examiner Tips and Tricks

When a metal conducts it is the electrons that are moving through the metal. When a salt solution conducts it is the ions in the solution that move towards the electrodes while carrying the electrons.

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Stewart Hird

Author: Stewart Hird

Expertise: Chemistry Lead

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

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