Lecture 15

# Lecture 15 - Homework chapter 9 15 19 21 25 27 29,31 33 35 39 51 53 19 21 25 27 29 33 35 39 51 53 61 63 Remember Hour exam Wed Nov 9 1 2 High

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Homework chapter 9: 15, 19, 21, 25, 27, 29,31. 33. 35, 39. 51, 53 61, 63 Remember: Hour exam Wed Nov 9 1

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High standard of living = high consumption of energy per person 3

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Chapters 9 and 10: Thermodynamics Thermodynamics: the conversion of energy amongst its various forms (mechanical, chemical, electrical, etc.) and the relation of these conversions to macroscopic variables (i.e. temperature, pressure, and volume) . Sadi Carnot Josiah W. Gibbs 1796-1832 1839-1903 “Reflections on the motive power of heat,” 1824 5 Thermochemistry: study of the energy evolved or absorbed in chemical reactions and in physical transformations, such as melting or boiling.

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Internal energy of any system Internal energy (E ): sum of the kinetic and potential energies of all the “particles” in the system. Change of Internal Energy during a process: E = q + w gg y g p q E = Final energy of system after process, minus initial energy of system before process. Alternative Form of First Law of Thermodynamics = hange ternal nergy E = change in internal energy q = heat [+ if heat flows into system , – if heat flows out of system w = work (+ if surroundings do work on system , – if system does work on urroundings) surroundings) 6
Thermodynamic calculations on ideal gases he simplest nd most important system onsider is a monatomic ideal gas The simplest and most important system to consider is a monatomic ideal gas Ideal gases obey the relation PV = nRT And for one mole E = (KE) vg mole = (3/2)RT where (KE) vg mole = average translational avg, mole avg, mole energy of 1 mol of gas at a given T (in K) note: ideal gas E is not a function of container volume V or pressure P, as ideal gas law ignores interactions between molecules Thus, the only way to change KE of an ideal gas is to change T nd the energy (heat) required to change KE f 1 mol of gas by T is: ad teeeg y (e a t )e que dtocag e oo o g a s b y s Energy (heat) required = (3/2)R T Molar Heat Capacity the energy (heat) required to raise the temperature of 1 mole by 1 K 7

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Process involving change of temperature eating a gas: Energy and Enthalpy Heating a gas: Energy and Enthalpy KE = (3/2)RT (per mole) Æ for a monatomic gas, KE = E For an ideal gas, to change KE, temperature must be increased E = (3/2)RT (per mole) = (3/2)R (per mole) ust a substitution; E (3/2)R T (per mole) C v =(3/2)R For a monatomic ideal gas, Just a subst tut o ; Not a comment suggesting the process need be at onstant volume E = C v T or C v (rather than C P ) appears in the expression constant volume E = nC v T (n moles) for E because, at constant V, all of the input energy goes into increasing E (i.e. no PV work)
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## This note was uploaded on 11/03/2011 for the course MATH 1090 taught by Professor Greenwood during the Spring '08 term at MIT.

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Lecture 15 - Homework chapter 9 15 19 21 25 27 29,31 33 35 39 51 53 19 21 25 27 29 33 35 39 51 53 61 63 Remember Hour exam Wed Nov 9 1 2 High

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