PChem312 f20 w5

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Monday, Sept 14, 2020

Announcement: Exam I (Ch 1 and 2), Thursday Sept 24th 2-6 pm

- books allowed

- notes allowed

- computers required (computers in CSB 377 will be available)

Section 2.10

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Section 2.11: Heat Capacity

- C_V,m - molar heat capacity at constant volume.

- C_P,m - molar heat capacity at constant pressure.

heat capacities are usually temperature dependent, so C_V,m(T) and C_P,m(T); more later in Ch 3.

- See Table 2.5: Molar Heat Capacity, CP,m(T), of Gases (298-800K), page 629.

Wednesday, Sept 16, 2020

Sec 2.11: continued

- Heat capacity plot/physical states (Figure 2.14 - Cl₂)

Relationship between C_V,m and C_P,m...

C_P - C_V = nR

C_P,m - C_V,m = R

Sec 2.12/2.13: FINALLY...Calculating ΔU...and more!

ΔU = q + w <-- 1st law of thermodynamics (mathematical form)

Case 1...

Consider a constant volume process where no expansion work (PV work) can be done...reminder for PV work, w = -PΔV...if constant volume (ΔV=0), then no expansion work...and then ΔU = q_V, where we add the subscript "V" on q to indicate constant volume.

ΔU = q_V

(we will work a few problems like this soon)

Note: it would be nice if there was an equivalent for constant pressure (the much more common why of doing experiments...

See "derivation" of ΔH (enthalpy - the second thermodynamic state function) (page 50-51).

ΔH = q_P

Thursday, Sept 17, 2020

0) Heat Capacity Plot (use data from Heating/Cooling worksheet)

- using Excel

- using Igor (Wavemetrics Igor 8.0 download/)

1) Thermal imaging camera - insulated mugs 2) Cowboy Coffee worksheet (here)