1. WARM UP Think back to the our thermodynamics unit. In any exothermic reaction, lots of heat is created quickly, and the reaction creates lots of entropy. What is entropy?

2. Entropy Chemistry II

3. Entropy (S) A measure of disorder/randomness – More disorder, higher entropy – Universe tends to move toward greater entropy

4. Entropy (S) Microstates (probable arrangements) – Ludwig Boltzmann – The more microstates, the higher the entropy

5. Second Law of Thermodynamics The entropy of the universe increases in a spontaneous process – Decreases in a non-spontaneous one

6. Entropy Calculations Standard entropy – From known data – Appendix 3 – Δ S rxn = S products – S reactants Unit is J/K·mol

7. Entropy Calculations Entropy and Energy – Δ S universe = Δ S rxn + -(Δ E) rxn – Heat production increases entropy

8. Third Law of Thermodynamics The entropy of a perfect/pure crystalline solid is zero at a temp of 0 K (absolute zero) – Perfect order

9. Third Law of Thermodynamics – Allows for standard entropy calculations Δ S = S final – 0

10. WRAP UP Predict the entropy change for the following: – Burning gas in your car – Melting ice – Locker clean-out day

11. WARM UP Define entropy. Explain the second law of thermodynamics. Why does the universe work this way?

12. VIDEO CLIP The Big Bang Theory – Season 1 Episode 2

13. WRAP UP 1.Use the standard entropies to calculate the standard entropy of: H 2(g) + ½ O 2(g)  H 2 O (l). (remember that you need to factor stoichiometry into your equation)