Topic: Potential Energy Curve Do Now: p.26

Spontaneous Processes no outside intervention =physical or chemical change that occurs with no outside intervention activation energy However, some energy may be supplied to get process started = activation energy Iron rusting 4Fe(s) + 3O 2 (g)  2Fe 2 O 3 (s)  H = kJ Combustion CH 4(g) + 2O 2(g)  CO 2(g) + 2H 2 O (l)  H = -891kJ

Can you think of others?

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Activation Energy & Reaction

Activation Energy = Energy needed to initiate reaction = Energy needed to initiate reaction Energy needed to overcome reaction barrier difference between where reactants start & top of hill Difference between reactants & activated complex

Energy Diagram of a Reaction Activated Complex = intermediate formed during conversion from reactants to products Reactants combine to form an unstable complex

Potential Energy Curve: Endothermic Products have more P.E. than reactants Start low, end high

Potential Energy Curve: Exothermic Products have less P.E. than reactants Start high, end low

Have to label 6 energies on curve: reactants & products 1.PE reactants 2.PE products 3.PE activated complex 4.E a forward reaction 5.E a reverse reaction  H

Time Time What kind of reaction is represented? PEreactants PE activated complex PE products E a forward rxn E a reverse rxn Enthalpy 

 H of reaction Enthalpy 

Time Time What kind of reaction is represented? PE of reactants PE of activated complex P.E. of products E a forwardrxn reverserxn Enthalpy 

 H of reaction Enthalpy 

Catalyst (in the body = enzyme) Substance that increases rate of reaction without itself being consumed – does not participate in reaction Lowers the activation energy for the reaction

DOES IT AFFECT ΔH? Catalysts do not affect ΔH