9.5-9.7 - What happens in Jurassic Park when we let Mother...

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1 Thermodynamics Kinetics Energy content of Will the rxn happen? by what mechanism will the reaction occur? Section 9.0 Enthalpy Heat content Entropy Disorder What happens in Jurassic Park when we let Mother Nature have her way? #1 The fences lose energy. In thermodynamic terms, reactions in which energy is lost are preferred (also know as exothermic, H < 0) #2 The dinosaurs spread out over the park. In thermodynamic terms, reactions in which energy is spread out are preferred (also know S > 0) Section 9.5 Can we predict if a process will occur on its own? ( i.e., if a process is spontaneous?) Processes in nature tend to lower energy E n = lo n = hi Excited GS Products Reactants E H < 0 exothermic Section 9.0 Can we predict if a process will occur on its own? Processes in nature tend to lower energy. Is evaporation an endothermic or exothermic process? E S L G S L G H ( i.e., if a process is spontaneous?) Is freezing an endothermic or exothermic process? Which will be spontaneous in this room at normal conditions (25 o C, 1 atm): evaporation or freezing of water? Section 9.5 E S L G If evaporation costs heat energy (enthalpy) and freezing releases heat energy (enthalpy) then why does the process that COSTS energy occur spontaneously at room temperature? S L G H Section 9.5 exothermic endothermic If only enthalpy determined if a process was spontaneous, A GLASS OF WATER AT ROOM TEMPERATURE WOULD TURN TO ICE What else contributes to spontenaity? S univ = S system + S sur > 0 S = Entropy (S) units J/K S univ > 0 for all spontaneous processes meaning whenever something spontaneous happens, the universe gets more messy. q heat (J) T temperature (K) Section 9.5
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2 Why is S univ > 0? Probability How many ways is your room neat? How many ways is your room messy? Section 9.5 1 One Neat Way: Many Messy Ways: How many states for a Solid vs. Gas? How many ways is a solid substance at the same energy? How many ways is a vaporized substance at the same energy? Section 9.5
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This note was uploaded on 03/30/2010 for the course CH 101 taught by Professor Bigham during the Fall '08 term at N.C. State.

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9.5-9.7 - What happens in Jurassic Park when we let Mother...

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