1. IV. Reaction Energy (p. 514 - 517)
Ch. 17 – Chemical Reactions
IV. Reaction Energy (p )
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2. Catalyst Goal Sheets Homework: pp. 193-195 due tomorrow
Science fair question/plan due Wednesday
Chemical Reactions quiz Thursday or Friday
Test corrections due Friday
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3. Objectives: Enthalpy
Explain collision theory – molecules must collide in order to react, and they must collide in the correct or appropriate orientation and with sufficient energy to equal or exceed the activation energy.
 Interpret potential energy diagrams for endothermic and exothermic reactions including reactants, products, and activated complex‒with and without the presence of a catalyst.
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4. A. Reaction Pathway
Shows the change in energy during a chemical reaction
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5. Chemical bonds When chemical bonds are formed, energy is released
Electrons are often dropping into a more stable arrangement from an excited state. They will release energy as light or heat
When chemical bonds are broken, energy is absorbed.
Energy is required to break bonds
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6. Activation Energy
Whether the reaction ends up releasing or absorbing energy, an initial input of energy is often required
How does this relate to collision theory?
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7. Objective 2.2.2
Describe the difference between endothermic and exothermic reactions
What evidence can you look for signs of an endothermic or exothermic reaction?
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8. 2H2(l) + O2(l)  2H2O(g) + energy
B. Exothermic Reaction
reaction that releases energy
products have lower PE than reactants
energy released
2H2(l) + O2(l)  2H2O(g) + energy
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9. C. Endothermic Reaction
reaction that absorbs energy
reactants have lower PE than products
energy absorbed
2Al2O3 + energy  4Al + 3O2
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