1. Oxidation and Reduction By the end of this lesson, you should be able to: 1.State that a metal element reacting to form a compound is an example of oxidation. 2.State that oxidation is a loss of electrons. 3.State that a compound reacting to form a metal element is an example of reduction. 4.State that reduction is a gain of electrons by a reactant in any reaction. 5.State that in a REDOX reaction, reduction and oxidation occur together.

2. Oxidation Oxidation can mean either the loss of electrons by a chemical or a reaction where a metal element forms a compound, e.g. Mg  Mg 2+ + 2e - silvery metal  colourless ions Mg + S  MgS Metal  compound

3. Reduction Reduction can mean either the gain of electrons by any chemical or a reaction where a compound forms a metal element, e.g. Cu 2+ + 2e -  Cu blue ions  Brown metal CuS  Cu + S compound  metal element

4. REDOX Reactions A redox reaction is a reaction in which oxidation and reduction reactions take place at the same time. Electrons lost by one substance during oxidation are gained by another substance during reduction, e.g. Cu 2+ + Mg  Cu + Mg 2+ All displacement reactions are redox reactions

5. e.g. the reaction between zinc metal and copper(II) sulphate solution. Zinc atoms lose electrons to the copper (II) ions. Copper (II) ions gain electrons to form solid copper.

6. The reaction between a metal and a dilute acid can also be considered to be a redox reaction. e.g. the reaction between magnesium and hydrochloric acid. Magnesium is oxidised and forms magnesium ions, whilst the hydrogen ions in the acid gain electrons (reduction) and form hydrogen gas.

7. To help you remember use OILRIG Oxidation Is Loss of electrons Reduction Is Gain of electrons

8. Question When zinc is added to copper sulphate a reaction takes place. a) Name the kind of reaction which takes place b) Write a balanced chemical equation for this reaction c) Name the spectator ion, and write the chemical equation without the spectator ion d) Write the two ion-electron equations and state which one represents oxidation and which one represents reduction.

9. Answers a)Displacement b) Zn(s) + Cu 2+ SO 4 2- (aq)  Zn 2+ SO 4 2- (aq) + Cu(s) c) SO 4 2- is the spectator ion Zn(s) + Cu 2+ (aq)  Zn 2+ (aq) + Cu(s) d) Zn(s)  Zn 2+ (aq) + 2e - OXIDATION Cu 2+ (aq) + 2e -  Cu(s) REDUCTION