1. Exothermic reaction, e.g. respiration Energy ‘exits’ reaction – heats surroundings Thermometer readings rises Endothermic reaction, e.g. photosynthesis Energy ‘enters’ reaction – cools surroundings Thermometer readings fall

3. Hydrated Anhydrous copper sulphate copper sulphate + water Exothermic reaction Endothermic reaction

4. N 2 + 3H 2 2NH 3 Exothermic reaction inc temperature, dec products dec temperature, inc products Endothermic reaction inc temperature, inc products dec temperature, dec products

5. N 2 + 3H 2 2NH 3 Smaller vol. of gas produced inc pressure, inc products dec pressure, dec products Larger vol. of gas produced inc pressure, dec products dec pressure, inc products

6. N 2 + 3H 2 2NH 3 Pressure: - The higher the better - High pressure is dangerous! - Compromise by using 200-350 atm Temperature: - Forward reaction is exothermic, so low temperature is preferred - But this makes reaction slow - Compromise by using 450 O C Catalyst: - Iron - Speeds up both sides of reaction

7. C3

8. Energy from fuels Acids & Alkalis Energy Calorimeter Think HSW! Bomb calorimeter 4.2J raises temp of 1 g of water by 1 degree Food high in carbs and fats have lots of energy!!  more than body needs  obesity A + B  C If 0.1 mole of reactants. Total mass of A and B is 100g. Temp start is 19.6, temp max is 26.1 Work out diff….6.5 (Don’t need to learn this, you would get this) So for 0.1 moles = 2730J For 1 mole 2730 x 10 = 27300J (27.3kJ) …..exothermic reaction ( as temp rise) = -27.3kJ/mol Energy change = mass x 4.2 x temp change

9. Energy changes Acids & Alkalis Energy Reaction = bond breaking ( endo) and bond making ( exo) EXOTHERMIC Energy required to break bonds in less than energy released when new bonds are formed ENDOTHERMIC Energy required to break bonds in greater than energy released when new bonds are formed CATALYST…. Lowers activation energy ∆H = - ve ∆H = + ve

10. Bond energies Acids & Alkalis Energy CH 4(g) + 2O 2(g)  2H 2 O (l) + CO 2(g) Identify the bonds…..stick diagrams! BondBond energy kJ/mol H-H436 Cl-Cl242 H-Cl431 O-H464 C-C347 C-O335 O=O498 ∆H = bond breaking - bond making Add up on the bonds in the reactants. This is bond energy needed to break the bonds Add up on the bonds in the products. This is bond energy needed to make new bonds. REMEMBER… making new bonds is an exothermic reaction…so it is always a –ve number

12. Example 1 BOND ENERGY (kJ/mol) H-H 436 N-H 391 N ≡ N 945 a) Complete the balanced symbol equation. b) Draw the structural formula. c) Calculate the energy in for the reactant bonds being broken. d) Calculate the energy out for the product bonds being made. e) Work out the overall change in energy Hydrogen + Nitrogen Ammonia

13. Example 2 BOND ENERGY (kJ/mol) O=O 498 H-H 436 O-H 464 a) Complete the balanced symbol equation. b) Draw the structural formula. c) Calculate the energy in for the reactant bonds being broken. d) Calculate the energy out for the product bonds being made. e) Work out the overall change in energy Hydrogen + Oxygen Water