1. Temperature and Heat Chapter 6 Section 1
Thermal Energy
Temperature and Heat
Chapter 6 Section 1

2. Contents Section 1 slide 3 - 30 Section 2 slide 31 - 58

3. Temperature
All matter is made of atoms & molecules

4. Temperature All matter is made of atoms & molecules
All these particles constantly move in a random fashion

5. Temperature All matter is made of atoms & molecules
All these particles constantly move in a random fashion
In all directions at different speeds

6. Temperature All matter is made of atoms & molecules
All these particles constantly move in a random fashion
In all directions at different speeds
Thus they have ________ energy

7. Kinetic Energy
Faster they move, the more KE they have -> hotter they are

8. Kinetic Energy
Faster they move, the more KE they have -> hotter they are
As they cool, they slow down

9. Kinetic Energy
Faster they move, the more KE they have -> hotter they are
As they cool, they slow down
Temperature is a measure of the average value of the kinetic energy of the particles in an object.

10. Temperature
SI Units are kelvins (K)

11. Temperature SI Units are kelvins (K)
Celsius scale is more commonly used.
1 K = 1 degree Celsius

12. Thermal Energy
Thermal energy is the sum of the KE + PE of all the molecules in an object.

13. Thermal Energy
Temperature is not a form of energy

14. Thermal energy increases when:
KE increases as molecules move faster (speed)
AND when
PE increases as the molecules move farther apart (separation)

15. Heat is the transfer of energy from
a body of higher temperature to a body of lower temperature. 

16. Heat is a form of energy so:
It is measured in joules

17. Heat is a form of energy so:
It is measured in joules
When you add ice to a drink, what is happening? Is the ice cooling the drink or is the drink warming the ice?
Remember the definition of HEAT!

18. Specific Heat of a substance:
Is the amount of heat needed to raise the temperature of 1 kg of that substance by 1°C.

19. Specific Heat of a substance:
Is the amount of heat needed to raise the temperature of 1 kg of that substance by 1°C.
Is measured in joules per kilogram per degree Celsius [J/(kg°C)]

20. Specific Heat of a substance:
Is the amount of heat needed to raise the temperature of 1 kg of that substance by 1°C.
Is measured in joules per kilogram per degree Celsius [J/(kg°C)]
Water = 4,184 [J/(kg°C)]
Wood = 1760 [J/(kg°C)]
Glass = 664 [J/(kg°C)]
Iron = 450 [J/(kg°C)]

21. Water molecules
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22. How does water cool things?
When heat is added to water, some of the heat has to break some of the bonds before the molecules can start moving faster.

23. How does water cool things?
When heat is added to water, some of the heat has to break some of the bonds before the molecules can start moving faster.
In metals, electrons can move freely. When heat is added, no strong bonds have to be broken before the electrons can start moving faster.

24. How does thermal energy change?
When heat flows into or out of the object.

25. How does thermal energy change?
When heat flows into or out of the object.
To calculate the change:
J = mass (kg) X ∆°C X specific heat or
Q = m(Tf –Ti)C
Q stands for change in thermal energy. C stands for the object’s specific heat.

26. Measuring Specific Heat
A calorimeter is a device that can be used to find the specific heat of a material.
In a calorimeter, an object that has been heated transfers heat to a known mass of water. This continues until the object and the water are the same temperature.

27. Calorimeter
The thermal energy released by the object equals the thermal energy absorbed by the water.
Cross section of a typical bomb calorimeter
Encyclopædia Britannica, Inc.
Cross section of a typical bomb calorimeter
Encyclopædia Britannica, Inc.

28. Molecules in a substance
Speed up when the slow down when the substance is substance is
so they have so they have
(more or less) kinetic energy
(more or less) kinetic energy

29. Molecules in a substance
Speed up when the slow down when the substance is substance is
heated
cooled
so they have so they have
less kinetic energy
more kinetic energy

30. Section 2 Transferring Thermal Energy

31. Transferring Thermal Energy
Occurs in three ways:
Conduction
Convection
Radiation

32. Transferring Thermal Energy
Occurs in three ways:
Conduction when particles of one substance bump into another substance & transfer kinetic energy
Convection
Radiation

33. Transferring Thermal Energy
Occurs in three ways:
Conduction when particles of one substance bump into another substance & transfer kinetic energy
Convection by movement of warmer & cooler fluids (liquid or gas) from one place to another
Radiation

34. Transferring Thermal Energy
Occurs in three ways:
Conduction when particles of one substance bump into another substance & transfer kinetic energy
Convection by movement of warmer & cooler fluids (liquid or gas) from one place to another
Radiation by electromagnetic waves through solids, liquids or gases

35. Transferring Thermal Energy
When heat is transferred through conduction, thermal energy is transferred from place to place without transferring matter. It is transferred by collisions between particles, not by movement of matter.

36. Transferring Thermal Energy
The best conductors are metals such as silver, copper & aluminum.
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37. Transferring Thermal Energy
The best conductors are metals such as silver, copper & aluminum.
Solids are better conductors than liquids which are also better than gases.

38. Transferring Thermal Energy
The best conductors are metals such as silver, copper & aluminum.
Solids are better conductors than liquids which are also better than gases.
Why is this?

39. Transferring Thermal Energy
The best conductors are metals such as silver, copper & aluminum.
Solids are better conductors than liquids which are also better than gases.
Why is this?
Think about the comparative space between particles…

40. Convection
A fluid is a substance that can flow.

41. Convection A fluid is a substance that can flow.
Their movement from one place to another creates currents.

42. Convection A fluid is a substance that can flow.
Their movement from one place to another creates currents.
Currents transfer heat.

43. Convection A fluid is a substance that can flow.
Their movement from one place to another creates currents.
Currents transfer heat.
Rising & sinking
action of hot and cold
creates convection
currents

44. Convection
Is different than conduction because it transfers thermal energy by moving particles from one place to another.

45. Convection
Is different than conduction because it transfers thermal energy by moving particles from one place to another.
Warm particles change places with cooler particles.

46. Convection
Is different than conduction because it transfers thermal energy by moving particles from one place to another.
Warm particles change places with cooler particles.
In conduction no particles move from place to place.

47. Radiation
Since there is almost no matter in space, energy travels from the Sun to Earth by radiation.
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48. Radiation
Since there is almost no matter in space, energy travels from the Sun to Earth by radiation.
Radiation travels through solids, liquids, gases and empty space.

49. When radiation strikes something,
Three things can happen:
Material absorbs
It reflects OR
It transmits some of the energy

50. The amount of energy absorbed, reflected, or transmitted …
Depends upon the type of material:
Light-colors reflect more
Dark colors absorb more
Works best in gases because the extra space between molecules allows it to travel more easily

51. Incoming & Outgoing Solar Radiation
(Credit - Steve Ackerman and Tom Whittaker)

52. Controlling Heat Flow How do animals control heat flow?
What are some things people use to control heat flow?

53. Insulator
Is a material in which heat flows slowly.

54. Insulator Is a material in which heat flows slowly. Wood Some plastics
Fiberglass
Air (gases are usually better insulators)
Insulators are the opposite of conductors.

55. How does a thermos work?
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56. How does a thermos work?
Has 2 glass walls with a vacuum between layers
Shiny aluminum coating inside & outside very reflective
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57. Thermal Energy
Section 3 Using heat

58. Heating Systems
Forced-Air system- common- furnace with ducts and returns

59. Heating Systems
Forced-Air system- common- furnace with ducts and returns
Radiator – furnace heats tank of water which is carried through pipes (conduction & convection)

60. Heating Systems
Forced-Air system- common- furnace with ducts and returns
Radiator – furnace heats tank of water which is carried through pipes (conduction & convection)
Electric heating – electrically heated coils in floors and walls (convection)

61. Solar Heating
Passive Solar Heating
Active Solar Heating

62. Solar Heating
Passive Solar Heating- Materials absorb heat during the day & then helps warm the house at night
Active Solar Heating

63. Solar Heating
Passive Solar Heating - Materials absorb heat during the day & then helps warm the house at night
Active Solar Heating – solar collectors absorb radiant energy heating air or water inside which is circulated by a pump to radiators

64. Thermodynamics…
Is the study of the relationship among thermal energy, heat and work.

65. First Law of Thermodynamics
The increase of the thermal energy of a system equals the work done on the system plus the heat transferred to the system
[Review open vs. closed system]

66. Second Law of Thermodynamics
The increase in thermal energy of a cool object equals the decrease in thermal energy of the warm object.

67. Second Law of Thermodynamics
The increase in thermal energy of a cool object equals the decrease in thermal energy of the warm object.
The second law says that it is impossible for heat to flow from a cool object to a warmer object unless work is done.

68. How does an internal combustion engine work?
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69. How does an internal combustion engine work?
Intake stroke – the intake valve opens as the piston moves downward, drawing a mixture of gasoline and air into the cylinder

70. How does an internal combustion engine work?
Compression stroke – Intake valve closes as the piston moves upward compressing the fuel-air mixture

71. How does an internal combustion engine work?
Power stroke – a spark plug ignites the fuel-air mixture. As the mixture burns, hot gases expand pushing the piston down

72. How does an internal combustion engine work?
Exhaust stroke – As the piston moves up, the exhaust valve opens and the hot gases are expelled out of the cylinder.

73. How does an internal combustion engine work?

74. Heat movers
If the second law is true, then HOW does a refrigerator work?

75. Heat movers
If the second law is true, then HOW does a refrigerator work?
Refrigerators contain a liquid coolant which is pumped through an expansion valve & changed into a gas cooling it. As it’s pumped through pipes in the refrigerator it absorbs thermal energy then is sent to a compressor

76. Heat movers – air conditioner
It’s similar to a refrigerator, except the warm air from the room is forced to pass over tubes containing coolant, then the cool air is forced back into the room. The thermal energy absorbed is transferred to the air outdoors.

77. Heat movers
Refrigerators and air conditioners are heat engines working in reverse.
They use mechanical energy supplied by the compressor motor to move thermal energy from cooler to warmer areas

78. How do energy transformations produce heat?
Usually when energy transformations occur, some heat is produced in the form of friction which is then transferred to the surroundings by conduction and convection.

79. Intake stroke- intake valve opens
Intake stroke- intake valve opens. Piston moves downward, gas mixture fills cylinder
_________Stroke
Compression stroke
__________stroke

80. Intake stroke- intake valve opens
Intake stroke- intake valve opens. Piston moves downward, gas mixture fills cylinder
Exhaust stroke – As the piston moves up, the exhaust valve opens and the hot gases are expelled out of the cylinder.
Compression stroke Intake valve closes as the piston moves upward compressing the fuel-air mixture
Four- stroke Cycle
Power stroke – a spark plug ignites the fuel-air mixture. As the mixture burns, hot gases expand pushing the piston down