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C7 energy levels
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  • 1. Energy Levels
  • 2. Energy Levels Exothermic reactions
    • Energy is given out
    • The products have less energy than the reactants
    Combustion and neutralisation are exothermic
  • 3. Energy Level Diagrams Exothermic reactions energy
  • 4. Energy Level Diagrams Exothermic reactions energy course of reaction
  • 5. Energy Level Diagrams Exothermic reactions energy course of reaction reactants
  • 6. Energy Level Diagrams Exothermic reactions energy course of reaction reactants products
  • 7. Energy Level Diagrams Exothermic reactions energy course of reaction reactants products energy given out ∆ H is negative
  • 8. 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
  • 9. Energy Level Diagrams Endothermic reactions energy
  • 10. Energy Level Diagrams Endothermic reactions energy course of reaction
  • 11. Energy Level Diagrams Endothermic reactions energy course of reaction reactants
  • 12. Energy Level Diagrams Endothermic reactions energy course of reaction reactants products
  • 13. Energy Level Diagrams Endothermic reactions energy course of reaction energy taken in ∆ H is positive reactants products
  • 14. Summary Table Exothermic reactions Endothermic reactions
  • 15. Summary Table Exothermic reactions Endothermic reactions Energy is given out to the surroundings Energy is taken in from the surroundings
  • 16. 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
  • 17. 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
  • 18. ∆ H 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
  • 19. Bond energies The energy needed to break a chemical bond
    • Different chemical bonds have different bond energies
    Chemical bond Bond energy, kJ/mole H―H 436 O=O 498 O―H 464
  • 20. Working out ∆H Draw an energy level diagram with all the reactants and products on it energy course of reaction 2H 2 + O 2 2H 2 O
  • 21. Working out ∆H Show all the bonds in the reactants energy course of reaction 2H 2 O H―H H―H O=O +
  • 22. Working out ∆H Show all the bonds in the products energy course of reaction H―H H―H O=O + H H O H H O
  • 23. Working out ∆H Show the bond energies for all the bonds energy course of reaction 436 436 O=O + H H O H H O
  • 24. Working out ∆H Show the bond energies for all the bonds energy course of reaction 436 436 498 + H H O H H O
  • 25. Working out ∆H Show the bond energies for all the bonds energy course of reaction 436 436 498 + 464 464 + H H O
  • 26. Working out ∆H Show the bond energies for all the bonds energy course of reaction 436 436 498 + 464 464 + 464 464 +
  • 27. Working out ∆H Add the reactants’ bond energies together energy course of reaction 464 464 + 464 464 + 1370
  • 28. Working out ∆H Add the products’ bond energies together energy course of reaction 1370 1856
  • 29. Working out ∆H ∆ H = energy in ― energy out energy course of reaction 1370 1856 1370 1856 ―
  • 30. Working out ∆H ∆ H = energy in ― energy out energy course of reaction 1370 1856 1370 1856 -486 ―
  • 31. Working out ∆H ∆ H = energy in ― energy out energy course of reaction 1370 1856 ∆ H = -486
  • 32. Working out ∆H Summary
    • The energy values have units of kJ/mole
    • In the exam, you will be given the energy values and all the bonds to make or break
    ∆ H is energy in – energy out
    • Energy goes in to break bonds
    • Energy goes out when bonds are made