physics unit 6: thermodynamics
DESCRIPTION
Physics Unit 6: Thermodynamics. “Thermodynamics”. Is derived from Greek meaning “movement of heat.”. The First Law of Thermodynamics. Official Definition: When heat flows in or out of a system, the energy it gains or loses is equal to the amount of heat transferred. Or… Energy = Heat - PowerPoint PPT PresentationTRANSCRIPT
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Physics Unit 6: Thermodynamics
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“Thermodynamics”
Is derived from Greek meaning “movement of heat.”
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The First Law of Thermodynamics Official Definition:
When heat flows in or out of a system, the energy it gains or loses is equal to the amount of heat transferred.
Or… Energy = Heat Is analogous to the Law of Conservation of Energy We are now dealing with Internal Energy
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Temperature: What is it?
How “Hot” or “Cold” a substance is. Temperature represents the average
translational kinetic energy of the individual particles in a system.
The Temperature Scales Fahrenheit – water freezes at 32oF and boils at 212oF Celsius – Water freezes at 0oC and boils
at 100oC Kelvin – is based off of Absolute Zero
Absolute Zero So cold that all particles stop moving! Total energy of the particles is 0.
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Specific Heat Capacity What is it?
The resistance to change in temperature of a substance.
The Equation: Q = mcΔT
Where:Q = heat addedm = mass of the samplec = specific heat capacityΔT = change in temperature
Examples:1. How much heat energy is required in order to raise the
temperature of a 0.5 kg iron nail from 25oC to 80oC? Q = mcΔT
Q = (0.5)(460)(55) = 12,650 Joules
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The Second Law of Thermodynamics Official Definition:
Heat, of itself, never flows from a colder object to a warmer object.
Energy always flows from Hot to Cold This law is also called the Law of Entropy
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What is Entropy? The amount of disorder in a system The universe is always moving towards more entropy Examples:
Ice melting Liquid water evaporating
It takes Work (energy) to decrease Entropy
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Types of Heat Transfer Conduction
Heat transfer between materials that are in direct contact with each other.
Convection Transfer in a fluid by movement of the substance itself.
Radiation Energy transmitted by electromagnetic waves.
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Phase Changes The States of Matter:
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Phase Changes Types of Phase Changes:
Melting Evaporation Condensation Boiling Sublimation
Melting
Condensation
EvaporationBoiling
Sublimation
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Phase Changes How do you change the melting point or boiling point of
a substance? Add a solute Change the pressure
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Phase Changes Energy During Phase Changes
What happens to the temperature of water as heat is added?
It Increases. What happens to the temperature during a phase change?
It remains constant.