1. Agenda:  Warm-up: Word Equations  Chemical reactions and energy  Endothermic or exothermic  How energy is represented in chemical reactions  Practice: Predicting products  Using types of reactions  Cards Homework:

2.  #13 Zinc II hydroxide + hydrochloric acid Zinc II chloride + water #17 Sodium carbonate + sulfuric acid Sodium sulfate + water + carbon dioxide

3. Representing the energy changes in reactions Thermo-chemistry

5. 1.When two chemicals mix their temperature rises: 2.A solid burns brightly and releases heat, light and sound: 3.When two chemicals are mixed their temperature drops: 4.Two chemicals will only react if you heat them continually: 5.Plants take in light energy for photosynthesis:

6. During chemical reactions, the bonds between atoms break and new bonds are formed. Energy must be absorbed to break bonds. When bonds are made, energy is released Copper II carbonate reacts to form copper II oxide and carbon dioxide Is this reaction endothermic or exothermic? Examine the bonds to determine the answer.

7. Notes: Representing energy in chemical reactions 1. Measurement of energy: joules Joules/gram or joules/mole 2. Energy shown as a reactant or product Endothermic: Exothermic: 3. Change in energy: ∆H (heat of reaction) Positive + ∆ Negative -∆ 4. Diagrams of the energy

8. ENERGY IN REACTIONS Exothermic reactions Energy is given out The products have less energy than the reactants Exothermic reactions are common. Combustion and neutralization (a special type of double replacement reactions) are exothermic

9. ENERGY LEVEL DIAGRAMS Exothermic reactions energy

10. ENERGY LEVEL DIAGRAMS Exothermic reactions energy course of reaction

11. ENERGY LEVEL DIAGRAMS Exothermic reactions energy course of reaction reactants

12. ENERGY LEVEL DIAGRAMS Exothermic reactions energy course of reaction reactants products

13. ENERGY LEVEL DIAGRAMS Exothermic reactions energy course of reaction reactants products energy given out ∆H is negative

14. ENERGY LEVEL DIAGRAMS Endothermic reactions Energy is taken in The products have more energy than the reactants The energy is taken in from the surroundings

15. ENERGY LEVEL DIAGRAMS Endothermic reactions energy

16. ENERGY LEVEL DIAGRAMS Endothermic reactions energy course of reaction

17. ENERGY LEVEL DIAGRAMS Endothermic reactions energy course of reaction reactants

18. ENERGY LEVEL DIAGRAMS Endothermic reactions energy course of reaction reactants products

19. ENERGY LEVEL DIAGRAMS Endothermic reactions energy course of reaction energy taken in ∆H is positive reactants products

20. SUMMARY TABLE Exothermic reactions Endothermic reactions

21. SUMMARY TABLE Exothermic reactions Endothermic reactions Energy is given out to the surroundings Energy is taken in from the surroundings

22. SUMMARY TABLE Exothermic reactions Endothermic reactions Energy is given out to the surroundings Energy is taken in from the surroundings ∆H is negative∆H is positive

23. SUMMARY TABLE Exothermic reactions Endothermic reactions Energy is given out to the surroundings Energy is taken in from the surroundings ∆H is negative∆H is positive Products have less energy than reactants Products have more energy than reactants

24. ∆H = ENTHALPY = CHANGE IN ENERGY How much energy is given out or taken in? Energy is needed to break chemical bonds Energy is given out when bonds are made ∆H is the difference between the energy needed to break the bonds in the reactants, and the energy given out when new bonds are made in the products

25. WORKING OUT ∆H Summary The energy values have units of kJ/mole ∆H is difference between energy in – energy out Energy goes in to break bonds Energy goes out when bonds are made

26.  Most exothermic reactions require energy to start the reaction. A catalyst speeds up a reaction by lowering the amount of activation energy needed. Energy Course of the reaction

27. the overall exothermic or endothermic energy change is the same for both the catalysed or uncatalysed reaction. The catalyst might help break the bonds BUT it cannot change the actual bond energies.

28. Practice: Reactions  Determine types of reactions  Determine if the reaction is endothermic or exothermic