05 Lecture 7 to 9 January 18,20,22

05 Lecture 7 to 9 - CHEM 350 Lecture 7 8 and 9 Introduction to Statistical Mechanics There are two general approaches to the description of

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CHEM 350 Lecture 7, 8, and 9, January 18, 20, and 22, 2010 Introduction to Statistical Mechanics. There are two general approaches to the description of physical systems: i) Macroscopic : large units of matter; units mol, mmol, etc. mechanical variables: V,N,P,U,H,. .. non-mechanical variables: T,S,A,G,. .. ii) Microscopic : physical system examined in terms of individual molecules and their motions. We can use either (a) Classical mechanics: specify values of x,y,z , p x ,p y ,p z , etc., for each molecule in the sample each complete set of such values makes up a microstate. or (b) Quantum mechanics: specify wave function ψ α ( x,y,z, ··· ) for each molecule in the sam- ple, together with the appropriate quantum numbers characterizing the MICROSTATE. It is appealing to attempt to explain or interpret macroscopic behaviour in terms of laws gov- erning the microscopic constituents, BUT how do we work out the detailed behaviour of so many particles? In principle, this problem is intractable from such a point of view. We need a new branch of physics. Still need laws of mechanics and electromagnetism, which are concerned with motions and properties of atoms, molecules, etc. Relinquish : idea of arriving at a detailed description of the particle motions. 1
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Questions to be answered : typically questions such as i) What is entropy; why does it always increase in spontaneous processes? ii) What is the value of the absolute entropy for a given chemical system? iii) Can the equilibrium constant for a chemical reaction be predicted from a knowledge of the properties of the individual reactants and products? If so, how? are the type of questions that can be answered by this type of physics.
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This note was uploaded on 04/11/2010 for the course CHEM 1101 taught by Professor Leroy during the Spring '10 term at University of Toronto- Toronto.

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05 Lecture 7 to 9 - CHEM 350 Lecture 7 8 and 9 Introduction to Statistical Mechanics There are two general approaches to the description of

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