What is Thermo, Stat Mech, etc.?

1. What is Thermo, Stat Mech, etc.? Statistical Mechanics Mechanics Classical Macroscopic Microscopic Molecular Atomic Random Coherent Quantum Thermo/Kinetics Thermodynamics is a funny subject. The first time you go through it, you don't understand it at all. The second time you go through it, you think you understand it, except for one or two small points. The third time you go through it, you know you don't understand it, but by then you are so used to it, it doesn't bother you any more. -- Arnold Sommerfield A theory is more impressive the greater is the simplicity of its premises, the more different are the things it relates, and the more extended its range of applicability. Therefore, the deep impression which classical thermodynamics made on me. It is the only physical theory of universal content which I am convinced will never be overthrown, within the framework of applicability of its basic concepts. -- Albert Einstein Our approach will be to focus on the macroscopic, thermodynamic and kinetic picture with occasional insight from the microscopic picture via statistical mechanics. Modified by Jed Macosko

2. Energy, Work and Heat • ________ is the capacity to do work. • Its classification into:________ ________ (by motion) (by position)e.g. thermal chemical, electricalIs purely for our convenience in visualizing the energy. • ________and ________are not “types” of energy, but are processes involving transfer of energy. They appear and disappear at the system boundary. They are ________. • ________is the transfer of energy from one body to another of lower temperature. • Convention: if heat flows into the system, q__0. • ________is the transfer of energy by some mechanism other than temperature difference. • Convention: if work is done on the system, w__0. • Heat stimulates random motion. • Work stimulates organized motion. • Work “degrades” into heat. • qualitative observations by Count Rumford (Ben Thompson) • quantitative measurements by James Joule Modified by Jed Macosko

3. ________properties depend on the amount of substance in the system, e.g. n, V. Terminology 1 A ________is a particular sample of matter or region of space. An ________does not interact with its ________. system + surroundings = ________ A ________________does not allow passage of mass over its boundaries, in contrast to… An ________________. An ________________has boundaries which permit no flow of heat. It is insulated. A system is in a definite ________when all its properties have definite values. A systemat ______________is time independent; it is not affected by the history of the system. ________properties are independent of amount, e.g. P, T. Modified by Jed Macosko

4. ________system matter heat surroundings ________system matter heat surroundings ________system matter heat surroundings Modified by Jed Macosko

5. Terminology 2 ________ ________(________ ________) uniquely determine the state of a system at equilibrium. Two samples of a substance with the same state variables are in the same state. The change in a state variable depends only on the initial and final states, independent of path. ________functions depend on the ________ and therefore vary with ________. A ________process is one in which the initial and final states are the same, i.e. no change in the state variables. In contrast, path functions generally have non-zero values for cyclic processes, dependent on the path. A ________ process is one that can be reversed by an infinitesimal modification of a variable. The system is in equilibrium with the surroundings at all times. This is an idealized situation, useful as a theoretical limit, but… All real processes are irreversible. It is possible to restore the system or the surroundings to their original states but not both. An ________of ________ is the functional relationship between the properties of a system, e.g, the ideal gas law. Modified by Jed Macosko

6. P1 V1 P P V P2 V2 T3 V3 P3 T1 V T T ________ ________ ________ Ideal Gases -- Review Ideal gases obey the ideal gas law: Pressure _______  1 N m-2  1 J m-3  1 kg m-1 s-2 Volume ________ 103 dm3  103 litres Temperature ________ no. of atoms in 12 g 12C number of moles gas constant but if P is in atm ( 1.01325  105 Pa) and V in litres, Modified by Jed Macosko

7. pressure 0 1 A _ _ B ________ Mixtures of Ideal Gases If the ideal gas law applies to each component, i ________pressure ________Law of ________Pressures e.g. for two components: Real gases are ideal only at the low density limit. Why? Modified by Jed Macosko