Energy and reactions: Make sure you revise: Exothermic and endothermic reactions Reversible reactions Test for water The Haber process Using ammonia

Exothermic and Endothermic Reactions In an exothermic reaction: heat is given out temperature of the surroundings increases. In an endothermic reaction: heat is taken in temperature of the surroundings decreases.

Anhydrous Copper Sulphate Hydrated Copper Sulphate Reversible Reactions This is the symbol for a reversible reaction: Reversible reactions are exothermic in one direction and endothermic in the other direction An example of a reversible reaction is when hydrated copper sulphate is heated to produce anhydrous copper sulphate. When this is left to cool it turns back into hydrated copper sulphate. The reverse reaction is used as a test for water. When water is added to anhydrous copper sulphate, 2 things happen: 1.) White solid turns blue, 2.) Reaction gives out heat. It’s an exothermic reaction (Takes in) Heat Endothermic Anhydrous Copper Sulphate (White Solid) Hydrated Copper Sulphate (Blue Solid) (Cool + Steam) Exothermic

Ammonia Ammonia dissolves in water to produce an alkaline solution Ammonia reacts with acids to produce ammonium salts Ammonium salts are important because they are used by farmers as fertilisers to help crops grow.

The Haber Process – making ammonia (NH3) The Haber Process uses nitrogen (from the air) and hydrogen (from natural gas) to produce ammonia which can be used to make fertilisers. The reaction uses a high temperature (450°C), high pressure (200 atmospheres) and an iron catalyst to produce a reasonable yield of ammonia. After they leave the converter, the gases are cooled, ammonia is removed as liquid and any unreacted nitrogen and hydrogen are recycled. The yield is less than 20% but the ammonia is produced quickly and no gases are wasted

Conditions in the Haber process Higher tier Exothermic  forward reaction N2 + 3H2  2NH3 4 molecules of gas 2 molecules of gas Backwards reaction  Endothermic Condition Action Effect Yield in the Haber Process: Temperature Increase Moves in endothermic direction More reactants (Nitrogen and Hydrogen) Decrease Moves in exothermic direction More product (ammonia) Pressure Moves in direction where there are LESS molecules Moves in direction where there are MORE molecules

Dynamic equilibrium and change Teacher notes This completing sentences activity could be used as a plenary or revision exercise on dynamic equilibrium. Students could be asked to write down the missing words in their books and the activity could be concluded by the completion on the IWB.