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Chapter 16

Chapter 16. Heat and Thermodynamics. Conduction . The transfer of thermal energy with no overall transfer of matter. Occurs within a material or between materials that are in contact. Conduction . Slower in gases than in liquids Slower in liquids than in solids

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Chapter 16

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  1. Chapter 16 Heat and Thermodynamics

  2. Conduction • The transfer of thermal energy with no overall transfer of matter. • Occurs within a material or between materials that are in contact.

  3. Conduction • Slower in gases than in liquids • Slower in liquids than in solids • Because the particles collide less often

  4. Thermal Conductors • A material that conducts thermal energy well • Examples: copper cooking pot, metal baking pan, tile floor

  5. Thermal Insulators • A material that conducts thermal energy poorly • Examples: wooden spoon, air, wool, foam

  6. Convection • The transfer of thermal energy when particles of a fluid move from one place to another

  7. Convection Currents • Occurs when a fluid circulates in a loop as it heats up and then cools down. • Important in many natural cycles: ocean currents, weather systems, movements of hot rock in the Earth’s mantle

  8. Radiation • The transfer of energy by waves moving through space • Examples: the sun heating Earth, heating coil on a stove or heater

  9. Radiation • All objects radiate energy. • As an object’s temperature increases, the rate at which it radiates energy increases. • Closer objects absorb more radiation and are heated more. • Further away objects absorb less radiation and are heated less.

  10. Radiation • Which receives more radiation and thus has more thermal energy, Earth or Mars? • Mercury or Earth? • Jupiter or Saturn?

  11. Thermodynamics • The study of conversions between thermal energy and other forms of energy.

  12. First Law of Thermodynamics • Energy is conserved. • When energy is added to a system it can either increase the thermal/heat energy or do work but is must be accounted for. • Remember energy can be neither created nor destroyed (only transferred).

  13. Second Law of Thermodynamics • Thermal energy can flow from colder objects to hotter objects only if work is done on the system. • A heat engine converts heat into work. • Thermal energy that is not converted into work is waste heat.

  14. Second Law of Thermodynamics • Spontaneous changes will always make a system less orderly, unless work is done on the system. • Disorder in the universe as a whole is always increasing. • You can only increase order on a local level.

  15. Second Law of Thermodynamics • Read the 2nd paragraph on page 483.

  16. Third Law of Thermodynamics • Absolute zero cannot be reached. • The closest that has been reached was 3 billionths of a kelvinabove absolute zero. • 0.000000003 K

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