EFFECT OF AN ELECTRIC CURRENT ON SUBSTANCES Archives

Introduction In any chemical reaction, the existing chemical bonds are broken and new chemical bonds are formed. Hence, all chemical reactions are fundamentally electrical in nature since electrons are involved in some way or the other in all types of chemical bonding. Many chemical reactions utilize electrical energy, whereas others can be used to produce electrical energy. As electrical energy involves the flow of electrons, these reactions are concerned with the transfer of electrons from one substance to the other. Conductors and insulators The ability to conduct electricity is the major simple distinction between elements that are metals and non-metals. Conductors A conductor is a material that conducts electricity but is not chemically changed in the process. All metals and graphite are conductors of electricity. Insulators An insulator is a material that does not conduct electricity. Such materials have no free electrons. Summary of Common Electrical Conductors These materials carry an electric current via freely moving electrically charged particles, when a potential difference (voltage) is applied across them, and they include: 1) All metals (molten or solid) and the non-metal carbon (graphite). This conduction involves the movement of free or delocalised electrons (e- charged particles) and does not involve any chemical change. 2) Any molten or dissolved material in which the liquid contains free moving ions is called the electrolyte. Ions are charged particles e.g. Na+ sodium ion, or Cl- chloride ion, and their movement or flow constitutes an electric current, because a current is moving charged particles. The movement of opposite charges during electrolysis is due to the attracting in the electric field produced by the potential difference (the voltage). Liquids that conduct must contain freely moving ions to carry the current and complete the circuit. You can't do electrolysis with an ionic solid! The ions are too tightly held by chemical bonds and can't flow from their ordered situation! When ionically bonded substances are melted or dissolved in water the ions are free to move about. However some covalent substances dissolve in water and form ions. e.g. hydrogen chloride HCl, dissolves in water to form 'ionic' hydrochloric acid H+Cl-(aq). See also SALTS BONDING IN METALS INTERMOLECULAR BONDING – VAN DER WAALS FORCES THE PHYSICAL PROPERTIES OF SILICON DIOXIDE THE PHYSICAL PROPERTIES OF GRAPHITE