Physics unit 6 thermodynamics
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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

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Physics Unit 6: Thermodynamics

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Physics unit 6 thermodynamics

Physics Unit 6: Thermodynamics


Thermodynamics

“Thermodynamics”

  • Is derived from Greek meaning “movement of heat.”


The first law of thermodynamics

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


Temperature

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.


Specific heat capacity

Specific Heat Capacity

  • What is it?

    • The resistance to change in temperature of a substance.

  • The Equation:

    • Q = mcΔTWhere:Q = heat addedm = mass of the samplec = specific heat capacityΔT = change in temperature

  • Examples:

    • How much heat energy is required in order to raise the temperature of a 0.5 kg iron nail from 25oC to 80oC?

      • Q = mcΔTQ = (0.5)(460)(55) = 12,650 Joules


The second law of thermodynamics

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


What is entropy

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


Types of heat transfer

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.


Phase changes

Phase Changes

  • The States of Matter:


Phase changes1

Phase Changes

Boiling

  • Types of Phase Changes:

    • Melting

    • Evaporation

    • Condensation

    • Boiling

    • Sublimation

Melting

Evaporation

Condensation

Sublimation


Phase changes2

Phase Changes

  • How do you change the melting point or boiling point of a substance?

    • Add a solute

    • Change the pressure


Phase changes3

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.


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