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Change of State and Laws of Thermodynamics. Section 12.2 Physics. Objectives. Define heats of fusion and vaporization. State the first and second laws of thermodynamics. Define heat engine, refrigerator, and heat pump. Define entropy. Change of State. Three most common states of matter:
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Change of State and Laws of Thermodynamics Section 12.2 Physics
Objectives • Define heats of fusion and vaporization. • State the first and second laws of thermodynamics. • Define heat engine, refrigerator, and heat pump. • Define entropy.
Change of State • Three most common states of matter: • Solid • Liquid • Gas http://thegreatwaterodyssey.com/images/soliqgas.gif
Changes of State • Phase Diagrams show the progression of a substance from a solid to a liquid to a gas. http://www.csd509j.net/chs/departments/science/physics/media/images/ch14/fig1.gif
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.
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.
Practice Problems • Pg. 289 • 11-14
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.
The First Law of Thermodynamics http://www.yourdictionary.com/images/ahd/jpg/A4piston.jpg
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.