Edexcel IGCSE Chemistry

Revision Notes

1.9.1 Explaining Conductivity

Conductivity of Covalent Compounds

  • Electric current is the flow of charged particles
    • This usually refers to electrons, but it could also mean the flow of ions
    • Collectively, they can be termed freely moving charged particles
  • Most covalent compounds do not conduct electricity as they have no freely moving charged particles to carry the current
  • They act as insulators and have many applications which rely on that property
  • Covalent substances are used as electrical insulators in solid, liquid and gaseous form
    • For example, sulfur hexafluoride is a dense gas used to insulate electrical transformers
    • Silicone oils and liquid hydrocarbons are also used in electrical equipment
  • Common insulators include the plastic coating around household electrical wiring:

Electrical Wire Insulated, IGCSE & GCSE Chemistry revision notes

Covalent compounds are used as insulating materials

  • There are some exceptions to conductivity in covalent compounds
    • Organic polymers have been developed which have multiple adjacent double bonds that allow electrons to migrate along the length of the polymer chains
    • These unusual materials have potential uses as electronic components and biomedical applications

Conductivity of Ionic Compounds

  • Ionic compounds can conduct electricity in the molten state or in solution as they have ions that can move and carry charge
  • They cannot conduct electricity in the solid state as the ions are in fixed positions within the lattice and are unable to moveMolten ionic substances conduct electricity, IGCSE & GCSE Chemistry revision notes

Molten or aqueous particles move and conduct electricity but cannot in solid form

Anions & Cations

  • 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

Transfer of Charge, IGCSE & GCSE Chemistry revision notes

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

Exam Tip

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.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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