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Physics

Physics. Chapter 10: Heat. Heat. What is Temperature? What “Feels” Warm? What “Feels” Cold? This is Only a Qualitative Measure. Heat. What is Temperature? Changing Temperature Requires the Transfer of Energy Heat May be Added or Removed. Heat. What is Temperature?

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Physics

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  1. Physics Chapter 10: Heat

  2. Heat • What is Temperature? • What “Feels” Warm? • What “Feels” Cold? • This is Only a Qualitative Measure

  3. Heat • What is Temperature? • Changing Temperature Requires the Transfer of Energy • Heat • May be Added or Removed

  4. Heat • What is Temperature? • Temperature is a Measurement of the KE of the Atoms within a Substance • Increase KE = Increase Temp • Decrease KE = Decrease Temp

  5. Heat • Thermal Equilibrium • The Transfer of KE Between Matter resulting in an Overall Balance of KE within the System

  6. Heat • Generally… • Matter Expands as Temperature is Increased • Matter Contracts as Temperature is Decreased

  7. Heat • Temperature Scales • Celsius • Fahrenheit • Kelvin

  8. Heat • Temperature Scales • Celsius • Water Freezes at 0oC • Water Boils at 100oC

  9. Heat • Temperature Scales • Fahrenheit • Water Freezes at 32oF • Water Boils at 212oF

  10. Heat • Temperature Scales • Converting Between Celsius and Fahrenheit

  11. Heat • Temperature Scales • Converting Between Celsius and Fahrenheit

  12. Heat • Temperature Scales • Kelvin • Water Freezes at 273.15K • Water Boils at 373.15K • SI Unit for Temperature

  13. Heat • Temperature Scales • Kelvin • In Range, 1 Kevin = 1oC

  14. Heat • Temperature Scales • Absolute Zero • 0 K • Lowest Possible Temperature • 0 Atomic KE Boomerang Nebula 2.7K

  15. Heat • Problem • The temperature of liquid nitrogen is 77K. What is this temperature in Celsius?

  16. Heat • Temperature Scales • Solution

  17. Heat • Problem • The temperature of liquid nitrogen is 77K. What is this temperature in Fahrenheit?

  18. Heat • Temperature Scales • Solution

  19. Heat • Problem • If you were told that your body temperature was 310.6K, what is this temperature in Fahrenheit?

  20. Heat • Temperature Scales • Solution

  21. Heat • Heat • Heat is Energy that Flows from a Higher Temperature Object to a Lower Temperature Object because of a Difference in Temperatures

  22. Heat • Heat (Q) • Units • Joules (J)

  23. Heat • First Law of Thermodynamics • The Internal Energy (U) of a System Changes from an Initial Value to a Final Value Due to Heat (Q) and Work (W)

  24. Heat • First Law of Thermodynamics • If Energy Enters the System • Positive Change in Energy • If Energy Leaves the System • Negative Change in Energy

  25. Heat • First Law of Thermodynamics • If Heat Enters the System • Positive Heat • If Heat Leaves the System • Negative Heat

  26. Heat • First Law of Thermodynamics • If Work is Done by the System • Positive Work • If Work is Done on the System • Negative Work

  27. Heat • Conservation of Energy

  28. Heat • The Second Law of Thermodynamics • Heat Flows Spontaneously from a Substance at a Higher Temperature to a Substance at a Lower Temperature and Does Not Flow Spontaneously in the Reverse Direction

  29. Heat • Homework • Pages 387 - 388 • Problems • 9 • 10 • 19 (7.9x104J) • 20 (a, 2.9J b, ?)

  30. Heat • Specific Heat Capacity • Energy Required to Change 1kg of a Substance Temperature 1oC • Based on… • Magnitude of Heat (Q) • Mass of Substance (m) • Change in Temperature (DT) • Specific Heat Capacity (c) (Table page 372)

  31. Heat • Specific Heat Capacity • Units • J/kg*Co

  32. Heat • Specific Heat Capacity • Ice • 2.09x103 J/kg*oC • Water • 4.186x103 J/kg*oC • Steam • 2.01x103 J/kg*oC

  33. Heat • Specific Heat Capacity • Solids and Liquids • Direct Heat Transfer • Gasses • Also Based on Pressure

  34. Heat • Specific Heat Capacity • Other Units (Mechanical Equivalent of Heat) • Kilocalorie • Heat Needed to Increase 1kg of Water by 1oC • 1 kcal = 4186 J • Calorie • Heat Needed to Increase 1g of Water by 1oC • 1 cal = 4.186 J

  35. Heat • Specific Heat Capacity • Calorimetry • Conservation of Energy (Heat) • Heat Transfer • Used to Determine Specific Heat Capacity

  36. Heat • Specific Heat Capacity • Calorimetry

  37. Heat • Specific Heat Capacity • Calorimetry

  38. Heat • Problem • While a person is exercising, 0.6kg of blood flows to the surface of the body and releases 2000J of energy. The blood arriving at the surface has a temperature of 37oC. Assuming that blood has the same specific heat capacity as water, determine the temperature of the blood leaving the surface and returning to the body.

  39. Heat • Solution • Ti = 37oC • Q = 2000J • c = 4186J/kgCo • m = 0.6kg

  40. Heat • Solution • Ti = 37oC • Q = 2000J • c = 4186J/kgCo • m = 0.6kg

  41. Heat • Problem • How many kg of hot water (49.0oC) must you mix with cold water (13.0oC) in a bath of 191kg to have a temperature of 36oC?

  42. Heat • Solution • Th = 49.0oC • Tc = 13.0oC • Tf = 36.00C • SHC = 4186J/kgCo • m = 191kg

  43. Heat • Solution • Th = 49.0oC • Tc = 13.0oC • Tf = 36.00C • c = 4186J/kgCo • m = 191kg

  44. Heat • Latent Heat Capacity (L) • Change of Phase • solid-liquid-gas • gas-liquid-solid • Sublimation • solid-gas • gas-solid

  45. Heat • Latent Heat Capacity (L) • Heat Required to Change the Phase of Mass of a Substance • Rearrangement of Structure • Units • J/kg

  46. Heat • Latent Heat Capacity (L) • Water • Lf = 3.33x105 J/kg • Lf = Latent Heat of Fusion • Lv = 2.42x106 J/kg • Lv = Latent heat of vaporization

  47. Heat • Latent Heat Capacity (L)

  48. Heat • Problem • A 10.0kg block of ice has a temperature of -10.0oC. The block absorbs 4.11x106J of heat. What is the final temperature of the water?

  49. Heat • Solution • Ti = -10.0oC • Q = 4.11x106J • c = 4186J/kgCo

  50. Heat • Solution • Ti = -10.0oC • Q = 4.11x106J • c = 4186J/kgCo

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