3a - Gibbs Bolzmann Kelvin Einstein Planck Clausius Carnot...

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1 Einstein Carnot Maxwell Clausius Gibbs Bolzmann Planck Kelvin Thermodynamics vs. Mechanics Focuses on dynamical processes. Focuses on systems in static equilibrium Microscopic (a molecular point of view). Macroscopic and phenomenological 17-th century (classical) 20-th century (quantum) 19-th century Mechanics Thermodynamics Statistical Mechanics bridges between the mechanical and thermodynamic approaches (for example – the kinetic theory of gases discussed in the previous chapter)
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2 Why do we need Thermodynamics??? •What determines the direction and equilibrium constant of a chemical reaction, and how does it depend on external parameters (temperature, pressure, etc.)? •What are the laws that govern phase transitions? •What are the limitations on the efficiency of power-producing and power-consuming devices (engines, solar cells, batteries, air conditioners, living organisms, etc.). •Why do some processes occur spontaneously and others don’t? •Why are some systems stable and others are not? All these questions, as well as many other questions, can be answered based on the THREE fundamental laws that form the basis of thermodynamics!!!
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3 Thermodynamics rests on the following empirical observation, which is true for practically all macroscopic systems: Macroscopic systems can exist in particular stationary states, called equilibrium states , that can be completely characterized by the values of a relatively small number of state functions , such as the internal energy, the volume, and the number of moles of the various components (the system’s composition). We can make a system change from one equilibrium state to another by removing a constraint . Many different paths can lead from one equilibrium state to another, depending on the details of how the constraint is being removed. Most of these paths involve complicated non-equilibrium states, that cannot be characterized by a small number of state functions. Thermodynamics is all about is being able to predict the values of the state functions at the final equilibrium state, based on their values at the initial equilibrium state, regardless of the path. Examples: •Chemical reaction •Expansion •Mixing •Heat exchange Cold Hot adiabatic diathermal Catalysis
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4 Different kinds of equilibrium Complete thermodynamic equilibrium requires the presence of three kinds of equilibrium: •Mechanical equilibrium: external forces are exactly balanced by internal forces. Example: equal external and internal pressures on a piston •Thermal equilibrium: A system is said to be in thermal equilibrium with its surroundings if both have the same temperature, such that there is no net heat flow between them. •Material equilibrium: No net transfer of matter to the environment and fixed composition. Example: Chemical equilibrium (equal rates of forward and backward reactions).
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This note was uploaded on 06/13/2009 for the course CHEM 260 taught by Professor Staff during the Spring '08 term at University of Michigan.

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3a - Gibbs Bolzmann Kelvin Einstein Planck Clausius Carnot...

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