D G = D H -T D S

1. DG = DH -TDS DH depends on the numbers and kinds (covalent and non-covalent) of BONDS made and broken upon going from initial to final state. DS depends on the mobilities and/or randomness (i.e. the number of iso-energetic states) of the system and surroundings upon going from initial to final state. The more isoenergetic states for a system, the greater the entropy of that system.

3. Changes in state functions are independent of pathway between initial and final states DU = Ufinal – Uinitial Thus, we can use real and/or imaginary pathways to evaluate changes in state functions. In practice we use imaginary pathways because they are easier to evaluate.

4. Thus, we can use real and/or imaginary pathways to evaluate changes in state functions. In practice we use imaginary pathways because they are easier to evaluate.

5. The internal energy, U, of an ideal gas is a function of temperature, pressure and volume.

8. Translation: Rotation:

9. The internal energy, U, of an ideal gas is a function of temperature, pressure and volume. DU= w + q, where w = work (ordered movement) and q = heat (disorderly movement).

10. We can imagine two different isothermal pathways between the same initial and final states. The change in state (e.g., DU) is the same; but, w and q differ for each pathway.

11. Irreversible vs. reversible pathway

13. Recall, we can use real and/or imaginary pathways to evaluate changes in state functions. In practice we use imaginary pathways because they are easier to evaluate. The pathways that are simplest to evaluate are: Isobaric (P= constant) Isochoric (V= constant) Isothermal (T= constant) reversible irreversible

15. Translation: Rotation:

16. A simplifying assumption we will make is that the heat capacity within a phase is constant