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Thermodynamics and Statistical Mechanics First Law of Thermodynamics.

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Presentation on theme: "Thermodynamics and Statistical Mechanics First Law of Thermodynamics."— Presentation transcript:

1 Thermodynamics and Statistical Mechanics First Law of Thermodynamics

2 Thermo & Stat Mech - Spring 2006 Class 32 Review of van der Waals Critical Values

3 Thermo & Stat Mech - Spring 2006 Class 33 van der Waals Results

4 Thermo & Stat Mech - Spring 2006 Class 34 van der Waals Results Substance P c v c /RT c He0.327 H2H O2O CO H2OH2O0.233 Hg0.909

5 Thermo & Stat Mech - Spring 2006 Class 35 Configuration Work đ W = PdV Gas, Liquid, Solid:

6 Thermo & Stat Mech - Spring 2006 Class 36 Kinds of Processes Often, something is held constant. Examples: dV = 0isochoric or isovolumic process dQ = 0adiabatic process dP = 0isobaric process dT = 0isothermal process

7 Thermo & Stat Mech - Spring 2006 Class 37 Work done by a gas For isochoric process dV = 0, so W = 0 For isobaric process dP = 0, so W = P V đW = PdV

8 Thermo & Stat Mech - Spring 2006 Class 38 Work done by a gas

9 Thermo & Stat Mech - Spring 2006 Class 39 Work done by an ideal gas For isothermal process dT = 0, so T = constant.

10 Thermo & Stat Mech - Spring 2006 Class 310 Isothermal Process

11 Thermo & Stat Mech - Spring 2006 Class 311 Heat Capacity Heat capacity measures the amount of heat that must be added to a system to increase its temperature by a given amount. Its definition: where y is a property of the system that is kept constant as heat is added.

12 Thermo & Stat Mech - Spring 2006 Class 312 Heat Capacity Properties that are usually kept constant for a hydrostatic system are volume or pressure. Then,

13 Thermo & Stat Mech - Spring 2006 Class 313 Heat Capacity Clearly, the heat capacity depends on the size of the system under consideration. To get rid of that effect, and have a heat capacity that depends only on the properties of the substance being studied, two other quantities are defined: specific heat capacity, and molar heat capacity.

14 Thermo & Stat Mech - Spring 2006 Class 314 Specific Heat Capacity Specific heat capacity is the heat capacity per mass of the system. A lower case letter is used to represent the specific heat capacity. Then, if m is the mass of the system,

15 Thermo & Stat Mech - Spring 2006 Class 315 Molar Heat Capacity Molar heat capacity is the heat capacity per mole of the system. A lower case letter is used to represent the molar heat capacity. Then, if there are n moles in the system,

16 Thermo & Stat Mech - Spring 2006 Class 316 Shorter Version Use heat per mass.

17 Thermo & Stat Mech - Spring 2006 Class 317 c P – c V đq = du + Pdv where u(T,v)

18 Thermo & Stat Mech - Spring 2006 Class 318 Constant Volume

19 Thermo & Stat Mech - Spring 2006 Class 319 Constant Pressure

20 Thermo & Stat Mech - Spring 2006 Class 320 Ideal Gas u is not a function of v.

21 Thermo & Stat Mech - Spring 2006 Class 321 Adiabatic Process For an ideal gas, and most real gasses, đQ = dU + PdV đQ = C V dT + PdV,. Then, when đQ = 0,

22 Thermo & Stat Mech - Spring 2006 Class 322 Adiabatic Process For an ideal gas, PV=nRT, so

23 Thermo & Stat Mech - Spring 2006 Class 323 Adiabatic Process

24 Thermo & Stat Mech - Spring 2006 Class 324 Adiabatic Process

25 Thermo & Stat Mech - Spring 2006 Class 325 Adiabatic Process

26 Thermo & Stat Mech - Spring 2006 Class 326 Adiabatic Process

27 Thermo & Stat Mech - Spring 2006 Class 327 for Ideal Gasses


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