Change of State and Laws of Change of State and Laws of ThermodynamicsThermodynamics

Section 12.2Section 12.2

PhysicsPhysics

ObjectivesObjectives

Define heats of fusion and vaporization.Define heats of fusion and vaporization. State the first and second laws of State the first and second laws of

thermodynamics.thermodynamics. Define heat engine, refrigerator, and heat Define heat engine, refrigerator, and heat

pump.pump. Define entropy.Define entropy.

Change of StateChange of State

Three most common states of matter:Three most common states of matter:– SolidSolid– LiquidLiquid– GasGas

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Changes of StateChanges of State

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

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Changes of StateChanges of State

Heat of FusionHeat of Fusion: The amount of energy : The amount of energy needed to melt one kilogram of a substance.needed to melt one kilogram of a substance.– The horizontal distance from a solid to a The horizontal distance from a solid to a

liquid on a phase diagram.liquid on a phase diagram.

Heat of VaporizationHeat of Vaporization: The amount of : The amount of energy needed to vaporize one kilogram of energy needed to vaporize one kilogram of a liquid.a liquid.– The horizontal distance from a liquid to a The horizontal distance from a liquid to a

gas on a phase diagram.gas on a phase diagram.

Changes of State Changes of State

The Heat Required to Melt = Q = mHThe Heat Required to Melt = Q = mHff

– m = mass; Hm = mass; Hff = Heat of Fusion = Heat of Fusion

The Heat Required to Vaporize = Q = mHThe Heat Required to Vaporize = Q = mHvv

– m = mass; Hm = mass; Hvv = Heat of Vaporization = Heat of Vaporization

– Table 12-2, pg 287 shows the heats of fusion Table 12-2, pg 287 shows the heats of fusion and vaporization for common substances.and vaporization for common substances.

Practice ProblemsPractice Problems

Pg. 289Pg. 289 11-1411-14

The First Law of ThermodynamicsThe First Law of Thermodynamics

The First Law of Thermodynamics:The First Law of Thermodynamics: the the total increase in the thermal energy of a total increase in the thermal energy of a system is the sum of the work done on it system is the sum of the work done on it and the heat added to it.and the heat added to it.

So, a system can increase its energy by two So, a system can increase its energy by two ways:ways:– Having work done on it.Having work done on it.– Having heat added to it.Having heat added to it.

The First Law of ThermodynamicsThe First Law of Thermodynamics

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The Second Law of ThermodynamicsThe Second Law of Thermodynamics

The Second Law of Thermodynamics:The Second Law of Thermodynamics: natural processes go in a direction that natural processes go in a direction that maintains or increases the total entropy of maintains or increases the total entropy of the universe.the universe.

Entropy:Entropy: a measure of the disorder in a a measure of the disorder in a system.system.

If you do not do any work on a system, If you do not do any work on a system, chaos will ensue.chaos will ensue.