Ch1b09Lecture10

# Ch1b09Lecture10 - 1 Parameters for Lennard-Jones Potential...

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1

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2 Parameters for Lennard-Jones Potential Table KT.2. Parameters for Lennard Jones Potential R e p u l si o n s ( a ll r t f i m il ) ra c
3 0 1E-21 2E-21 3E-21 0 0.5 1 1.5 2 2.5 Lennard Jones ε parameter Van der Walls a parameter H 2 CH 4 N 2 O 2 Ar 3.1E-10 3.5E-10 3.9E-10 0.025 0.03 0.035 0.04 0.045 σ Van der Walls b parameter H 2 4 N 2 O 2 A plot showing the similarity of the Lennard Jones Potential parameters and the parameters used for the van der Walls equation of state. Both of these models are attempts at explaining the same thing. The Lennard-Jones & the Van der Waals equation of state describe similar physics 12 6 () 4 Vr RR σσ  =−   () 2 2 n Pa V n b n R T V +− =

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4 Would you buy stock in this company??
5 The first law of thermodynamics: you can't get more energy out than you put in Or Energy is conserved

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6 Different pathways can require differing amounts of work. Example: traveling from San Diego to San Francisco
7 For certain issues – it only matters where you started and where you end A quantity like this is called a state function. end start

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8 Thermodynamic Processes and Thermochemistry The goal of thermodynamics: predict what chemical and physical processes are possible, and under what conditions, and to calculate quantitatively the properties of the equilibrium state that ensues when a process is carried out.
9 Much of thermodynamics involves first defining the system Can heat get in or out of the system? Can mass get in or out of the system? Can the system expand or contract? Can the # of particles inside the system change? Is the system changing? What is outside the system? These (and other) aspects are all important

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Thermodynamic Systems: Definitions •( a ) An open system can exchange matter and energy with its surroundings.
11 Thermodynamic Systems: Definitions •( a ) An open system can exchange matter and energy with its surroundings. b ) A closed system can exchange energy with its surroundings, but it cannot exchange matter. A lid has been placed on the coffee cup CLOSED SYSTEM

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12 Thermodynamic Systems: Definitions •( a ) An open system can exchange matter and energy with its surroundings. b ) A closed system can exchange energy with its surroundings, but it cannot exchange matter. • (c) An isolated system can exchange neither energy nor matter with its surroundings. The coffee has been poured into a thermos ISOLATED SYSTEM