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Chapter 11 Energy in Thermal Processes

Chapter 11 Energy in Thermal Processes. Temperature and heat Heat ( Q ): energy transferred between a system and its environment because of a temperature difference that exists between them SI Unit: Joule Alternative unit: calorie (cal):. Q. Q. Absorption of heat

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Chapter 11 Energy in Thermal Processes

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  1. Chapter 11 Energy in Thermal Processes

  2. Temperature and heat • Heat (Q): energy transferred between a system and its environment because of a temperature difference that exists between them • SI Unit: Joule • Alternative unit: calorie (cal):

  3. Q Q • Absorption of heat • Specific heat (c): heat capacity per unit mass • Common states (phases) of matter: solid, liquid, gas • Latenet heat (L): the amount of energy per unit mass transferred during a phase change (boiling, condensation, melting, freezing, etc.)

  4. Q Q Absorption of heat

  5. Absorption of heat

  6. Absorption of heat

  7. Chapter 11 Problem 17 A 100-g aluminum calorimeter contains 250 g of water. The two substances are in thermal equilibrium at 10°C. Two metallic blocks are placed in the water. One is a 50-g piece of copper at 80°C. The other sample has a mass of 70 g and is originally at a temperature of 100°C. The entire system stabilizes at a final temperature of 20°C. Determine the specific heat of the unknown second sample.

  8. Thermal conductivity • Heat transfer mechanisms • Thermal conduction • Conduction rate: • Thermal resistance: • Conduction through a composite rod:

  9. Heat transfer mechanisms

  10. Chapter 11 Problem 36 A box with a total surface area of 1.20 m2 and a wall thickness of 4.00 cm is made of an insulating material. A 10.0-W electric heater inside the box maintains the inside temperature at 15.0°C above the outside temperature. Find the thermal conductivity k of the insulating material.

  11. Emissivity Josef Stefan (1835-1893) • Heat transfer mechanisms • Thermal radiation • Radiation rate: • Stefan-Boltzmann constant: • Absorption rate:

  12. Chapter 11 Problem 46 At high noon, the Sun delivers 1.00 kW to each square meter of a blacktop road. If the hot asphalt loses energy only by radiation, what is its equilibrium temperature?

  13. Heat transfer mechanisms • Convection

  14. Heat transfer mechanisms

  15. Questions?

  16. Answers to the even-numbered problems Chapter 11 Problem 4 0.152 mm

  17. Answers to the even-numbered problems Chapter 11 Problem 12 467 pellets

  18. Answers to the even-numbered problems Chapter 11 Problem 16 1.7 kg

  19. Answers to the even-numbered problems Chapter 11 Problem 20 49 kJ

  20. Answers to the even-numbered problems Chapter 11 Problem 40 7.2 × 10-2 W/(m °C)

  21. Answers to the even-numbered problems Chapter 11 Problem 50 14.1 h

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