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

Example Problem 2.1-like

Sec 2.6: Irreversible Work, continued

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

Sorry...still drawing a bunch of diagrams to help clarify the processes...i will send email when complete.

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.

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.

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 P_i V_i -->P_f V_f along the same path.

work is equal to the red area under the curve.

Thursday, Sept 10, 2020

- Thermometer (cont.)

• Fill thermometer
• Calibrate thermometer
• Seal thermometer