1. www.thescienceteacher.co.ukwww.thescienceteacher.co.uk | resources for science teachers who like to think TopicEnthalpy changes and energy level diagrams LevelGCSE (or any course for students aged 14-16) Outcomes1.To understand the terms exothermic and endothermic 2.To be able to draw energy level diagrams for endothermic and exothermic reactions 3.To draw a catalyst on an energy level diagram

2. Progress of reaction Reactants (Fuel + oxygen) Where would the products go on this energy level diagram? Energy (joules)

3. Progress of reaction Reactants (Fuel + oxygen) Products (carbon dioxide + water) ΔH = negative Energy (joules)

4. Progress of reaction Reactants ΔH = positive or negative? ΔT(surroundings) = positive or negative? Products Energy (joules)

5. Progress of reaction Reactants ΔH = positive or negative? ΔT(surroundings) = positive or negative? Products Energy (joule)

6. Progress of reaction Reactants ΔH = positive or negative? ΔT(surroundings) = positive or negative? Products Energy (joule)

7. Progress of reaction Reactants ΔH = positive or negative? ΔT(surroundings) = positive or negative? Products Energy (joule)

8. Before the reaction could begin, the man had to light the fire with a match. Can you show this on your energy level diagram? We call the minimum energy need to start a reaction the activation energy or E a

9. Progress of reaction Reactants (fuel + oxygen) Products (carbon dioxide + water) ΔH Energy (joules) EaEa

10. Progress of reaction Energy (joule) Which colour line represents the enthalpy change? Which colour line represents the activation energy?

11. Draw your own energy level diagrams 1.A reaction with a small activation energy where ΔH is negative 2.An enothermic reaction with a large activation energy 3.The reaction between Mg and O 2 4.The combustion of petrol 5.The reaction inside an ice pack 6.Melting snow