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HEAT ENERGY IN REACTIONS

HEAT ENERGY IN REACTIONS. Success Criteria 1. I can explain the difference between an exothermic and endothermic reaction and give examples of each. STARTER. Compare the electrical conductivity of the 4 solid types: ionic, molecular, giant covalent network and metallic

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HEAT ENERGY IN REACTIONS

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  1. HEAT ENERGY IN REACTIONS Success Criteria 1. I can explain the difference between an exothermic and endothermic reaction and give examples of each

  2. STARTER • Compare the electrical conductivity of the 4 solid types: ionic, molecular, giant covalent network and metallic • Give a detailed explanation for each type

  3. HEAT • What is heat? • Describe the way it travels

  4. TYPES OF HEAT REACTIONS • Exothermic = release of heat energy into surroundings • Endothermic = absorption of heat energy from surroundings

  5. PRACTICAL • Practical 11.1 p138

  6. STARTER • You have a beaker of water Describe what • An endothermic reaction will do to it and why • An exothermic reaction will do to it and why

  7. WHERE DOES THE ENERGY COME FROM? • Bond making requires energy = ENDOTHERMIC • Think about freezing water, what kind of bonds (attraction) are we making? • Bond breaking releases energy = EXOTHERMIC • Think about boiling water, we overcome intermolecular bonds (attraction) which is released as heat • Exothermic = energy to break bonds > energy to make bonds • Endothermic = energy to make bonds > energy to break bonds

  8. COMBUSTION • All combustion reactions are exothermic • They release heat COMBUSTION OF HYDROGEN • Bonds broken = • Bonds made = • Energy of bonds broken > energy of bonds made 2H2 + O2 2H2O

  9. COMBUSTION OF METHANE CH4 + O2 CO2 + 2H2O • Bonds broken = • Bonds made =

  10. ENTHALPY • Enthalpy is the term for the heat energy in a substance due to kinetic energy of particles and potential energy of bonds • It has the symbol H • We measure enthalpy change between REACTANTS and PRODUCTS • Remember P comes before R in the alphabet

  11. ENERGY DIAGRAMS • Exothermic • Hr > Hp • H = Hp – Hr • H = negative • Endothermic • Hp > Hr • H = Hp – Hr • H = positive

  12. ACTIVATION ENERGY

  13. HOMEWORK • Read p138-139 • Do 11A Energetic Reactions on p140

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