PChem312 f20 w3

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Monday, Aug 31, 2020

Continue reading chapter 2

Sec 2.1: Internal Energy and !st Law of Thermodynamics

U <-- internal energy (1st thermodynamic state function)

U_f - U_i = ΔU, the change in the internal energy

• we cannot measure U_f or U_i, only ΔU.

First Law of Thermodynamics: the change in the system's internal energy is equal to, but opposite in sign, to the change in the surround's internal energy.

ΔU_sys = - ΔU_surr

How does one measure ΔU?

- changes in the system variables (ΔP, ΔV, ΔT, Δn) are an indication of ΔU; changes in system variables result in either heat (q) transfer or work (w) being done on or by the system; calculation of q or w leads directly to ΔU.

ΔP, ΔV, ΔT, Δn --> q (heat), w (work) --> ΔU

Thursday, Sept 3, 2020

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