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Physics Unit 6: Thermodynamics

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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  1. Physics Unit 6: Thermodynamics

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

  3. 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

  4. 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.

  5. 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

  6. 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

  7. 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

  8. 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.

  9. Phase Changes • The States of Matter:

  10. Phase Changes Boiling • Types of Phase Changes: • Melting • Evaporation • Condensation • Boiling • Sublimation Melting Evaporation Condensation Sublimation

  11. Phase Changes • How do you change the melting point or boiling point of a substance? • Add a solute • Change the pressure

  12. 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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