1. Lon-Capa 4th HW assignment due Friday, 10/7, 5 pm. It is open now.
3rd Quiz due Sunday, 10/9 by 10 pm. It will open Friday, 10/7 at 5 pm.
5th HW assignment is also open!
Three new videos (for Section 9.3). Please watch by Friday.

2. Chapter 9: Problem #117
This problem is an application of Hess’s law, although it may not be obvious upon reading it.

3. Chapter 9: Problem #122

4. We know it should. But why?

5. Signs of values Ideal gas expanding into a vacuum: E H q w
b) — + + —
c) 0 0 — + d)
e) I am not sure about this.

6. Questions To Consider
How can we predict which reactions are spontaneous (and what do we mean by spontaneous)?
How can we provide support (mathematical and qualitative) for observations?
Ice cream melts
Coffee cools
Why do systems reach equilibrium? That is, why doesn’t the ball go all the way down the hill?

7. Temperature: measure of KEavg

8. How to Think About Entropy
Entropy is related to heat/temperature.
ΔS = qrev/T
Entropy as “disorder”.
S = k●logW

9. We will… …show how probability plays into all of this.
…show that thermal equilibrium is preferred when two bodies of different temperatures are put in contact with one another.
…see why entropy is related to the logarithm of the number of configurations or microstates.
…discuss what “reversible” means when we say the change is entropy equals qrev/T?