1. Change of State and Laws of Thermodynamics
Section 12.2
Physics

2. Objectives Define heats of fusion and vaporization.
State the first and second laws of thermodynamics.
Define heat engine, refrigerator, and heat pump.
Define entropy.

3. Change of State Three most common states of matter: Solid Liquid Gas

4. Changes of State
Phase Diagrams show the progression of a substance from a solid to a liquid to a gas.

5. Changes of State
Heat of Fusion: The amount of energy needed to melt one kilogram of a substance.
The horizontal distance from a solid to a liquid on a phase diagram.
Heat of Vaporization: The amount of energy needed to vaporize one kilogram of a liquid.
The horizontal distance from a liquid to a gas on a phase diagram.

6. Changes of State The Heat Required to Melt = Q = mHf
m = mass; Hf = Heat of Fusion
The Heat Required to Vaporize = Q = mHv
m = mass; Hv = Heat of Vaporization
Table 12-2, pg 287 shows the heats of fusion and vaporization for common substances.

7. Practice Problems
Pg. 289
11-14

8. The First Law of Thermodynamics
The First Law of Thermodynamics: the total increase in the thermal energy of a system is the sum of the work done on it and the heat added to it.
So, a system can increase its energy by two ways:
Having work done on it.
Having heat added to it.

9. The First Law of Thermodynamics

10. The Second Law of Thermodynamics
The Second Law of Thermodynamics: natural processes go in a direction that maintains or increases the total entropy of the universe.
Entropy: a measure of the disorder in a system.
If you do not do any work on a system, chaos will ensue.