PChem312 f20 w4

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Monday, Sept 7, 2020

Review: The first Law of thermodynamics: ΔU = q + w

Sec 2.5: Reversible Work, continued

Screen Shot 2020-09-07 at 8.31.16 AM.png

Example Problem 2.1-like

Sec 2.6: Irreversible Work, continued

Screen Shot 2020-09-07 at 8.28.46 AM.png

Example Problem 2.2-like

Sec 2.7: Other Work

focus on electrical work, Example Prob 2.3c

Sec 2.8: State Functions and Path Functions

READ

Wednesday, Sept 9, 2020

Sec 2.9: Comparing Work/Indicator Diagrams

Irreversible Work

The following shows a PV diagram, also known as an indicator diagram. The center figure is Fig. 2.7 in your text. The outside "cylinders" are my annotation to clarify the diagram. I have separated the "expansion" (irreversible, isothermal) work from the "compression" (irreversible isothermal) work.


PV 02 Irrev IsoT Exp.png


Starting at an initial state (P1, V1; red dot), when we remove the weight quickly, but do not allow the system to change volume, we find ourselves in a temporary/fictitious/non-equilibrium state (P2, V1; green dot). The irreversible work is then done under P2 (P2 < P1) ending in the final state (P2, V2; yellow dot). Work was done by the system hence has a negative value.


PV 03 Irrev IsoT Comp.png


Starting at an initial state (P2, V2; green dot), when we add the weight quickly, but do not allow the system to change volume, we find ourselves in a temporary/fictitious/non-equilibrium state (P1, V2; pink dot). The irreversible work is then done under P1 (P1 > P2) ending in the final state (P1, V1; yellow dot). Work was done on the system hence has a positive value.
Reversible Work

Reversible work is a bit more straight forward. There are no fictitious/non-equilibrium states. The system moves between Pi Vi -->Pf Vf along the same path.

Screen Shot 2020-09-07 at 8.31.16 AM.png

work is equal to the red area under the curve.

PV 04 Rev IsoT Exp.png


PV 04 Rev IsoT Comp.png

Thursday, Sept 10, 2020

- Thermometer (cont.)
- Indicator Diagram Worksheet

Friday, Sept 11, 2020

Sec 2.9: Comparing Work/Indicator Diagrams

continued...