Concepts.doc (Word 97) KEY CONCEPTS FOR EXAM #1 Note: This list is only a guide to help you study. It is NOT comprehensive, and the exam may cover any topics discussed in class. Equations of State Ideal PV = nRT Van der Waals First Law of Thermodynamics For an irreversible expansion against a constant external pressure For an isothermal reversible expansion, At constant volume, w = 0; if there is no non-expansion work, then Other Topics: thermochemistry Enthalpy At constant pressure (with no non-expansion work), Joule Experiment Expansion into a vacuum Joule tried to measure the change in temperature with volume at constant U; No work was done because the gas was expanding against a vacuum (Pext = 0, w = 0) For an ideal gas, the temperature will not change because no work is done. For a real gas, the temperature will decrease slightly (although Joule was not able to measure any change in temperature because his equipment was not sensitive enough) For an ideal gas, mJ = 0 Joule-Thomson Experiment Expansion at constant H (isenthalpic) A gas at high pressure expands through a throttle valve into an area of lower pressure. The container is insulated so that the expansion is adiabatic. For an ideal gas, mJ-T = 0 For real gases, the Joule-Thomson coefficient is a property of the material that depends on temperature and pressure. The Joule-Thomson inversion temperature is the temperature above which mJ-T is negative, and below which mJ-T is positive. When mJ-T is negative, the gas will warm upon expansion. When mJ-T is positive, the gas will cool upon expansion. Heat Capacities At constant volume, At constant pressure, Second Law of Thermodynamics Similarly, For an ideal gas: For mixing, the total entropy change is and the entropy change per mole of mixture is For a reversible adiabatic process, DS = 0 Maxwell Relations Isothermal Compressibility Coefficient of Thermal Expansion Gibbs Helmholtz Criteria for spontaneity At constant P and T … DG < 0 At constant V and T … DA < 0 At constant V and S … DU < 0 At constant P and S … DH < 0 Other Concepts State vs. path functions Exact vs. inexact differentials; Euler's Relation Reversible vs. irreversible processes Open, closed, isolated systems; homogeneous vs. heterogeneous systems; singular vs. compound systems; partitioned systems; etc. Different types of processes: isothermal, isopiestic (isobaric), isochoric, isoenthalpic, isoentropic, adiabatic Equipartition of energy, how it is used to predict energies and heat capacities Boltzman expression Critical V, P, T Carnot Cycle Clausius Inequality Third Law of Thermodynamics Relevant pages in Mortimer are up to and including Section 5.2. Note: This list is only a guide to help you study. It is NOT comprehensive, and the exam may cover any topics discussed in class.