1. Today’s special Welcome back! New seating chart! Exam results
Presentation feedback
Late work policy
Attendance policy for this class
Vocab 16 Thermal E & heat-due next time
Video-Forces & Heat

2. Today’s special
HW check
Notes 16.1
HW I due next time

3. Late work
1. Do your work on time to enhance your learning and to contribute to the academic environment of the class
2. If you fail to do #1 you can turn in your work late if you attend a full session of homework club
-Full credit potential if you attend the next hw club
-70% potential if you attend within 1 week
-30% potential if you attend within 2 weeks
-10% max if turned in before the end of the grading period

4. Formal academic environment
 Treating pupils with care, fairness and consistency; boosting student-teacher acceptance of diversity; and reducing the emphasis on student competition represent successful methods. It is also important to promote student decision-making, individual and civic responsibility and commitment to the larger school community in order to improve school climate.

5. Work and Heat
In what direction does heat flow spontaneously?
Heat is the transfer of thermal energy from one object to another because of a temperature difference.
Heat flows spontaneously from hot objects to cold objects.

6. Temperature
What is the temperature of an object related to?
Temperature is related to the average kinetic energy of the particles in an object due to their random motions through space.

7. Temperature
Temperature is a measure of how hot or cold an object is compared to a reference point.
On the Celsius scale, the reference points are the freezing and boiling points of water.
On the Kelvin scale, absolute zero is defined as a temperature of 0 kelvins.

8. Temperature
As an object heats up, its particles move faster, on average. The average kinetic energy of the particles increases.
One way that heat flows is by the transfer of energy in collisions.
On average, high-energy particles lose energy. Low-energy particles gain energy.
Overall, collisions transfer thermal energy from hot to cold objects.

9. Thermal Energy
What two variables is thermal energy related to?
Thermal energy is the total potential and kinetic energy of all the particles in an object.
Thermal energy depends on the mass, temperature, and phase (solid, liquid, or gas) of an object.

10. Thermal Energy
Thermal energy depends on mass and temperature.
The tea is at a higher temperature than the lemonade.
The lemonade has more thermal energy because it has many more particles.

11. Thermal Contraction and Expansion
What causes thermal expansion?
Thermal expansion is an increase in the volume of a material due to a temperature increase.
Thermal expansion occurs when particles of matter move farther apart as temperature increases.

12. Specific Heat
How is a change in temperature related to specific heat?
Specific heat is the amount of heat needed to raise the temperature of one gram of a material by one degree Celsius.
The lower a material’s specific heat, the more its temperature rises when a given amount of energy is absorbed by a given mass.

13. Specific Heat

14. Specific Heat
In this formula, heat (Q) is in joules, mass (m) is in grams, specific heat (c) is in J/g•°C, and the temperature change (Δt) is in degrees Celsius.

15. Specific Heat
Calculating Specific Heat
An iron skillet has a mass of grams. The specific heat of iron is J/g•°C. How much heat must be absorbed to raise the skillet’s temperature by 95.0°C?

16. Specific Heat
Read and Understand
What information are you given?

17. Specific Heat
Read and Understand
What information are you given?

18. Specific Heat
Plan and Solve
What unknown are you trying to calculate?
What formula contains the given quantities and the unknown?

19. Specific Heat
Plan and Solve
What unknown are you trying to calculate?
What formula contains the given quantities and the unknown?

20. Specific Heat
Plan and Solve
Replace each variable with its known value.

21. Specific Heat
Plan and Solve
Replace each variable with its known value.

22. Specific Heat
Look Back and Check
Is your answer reasonable?

23. Round off the data to give a quick estimate.
Specific Heat
Look Back and Check
Is your answer reasonable?
Round off the data to give a quick estimate.
Q = 500 g × 0.5 J/g•°C × 100°C = 25 kJ
This is close to 21.4 kJ, so the answer is reasonable.

24. Specific Heat
1. How much heat is needed to raise the temperature of g of water by 85.0°C? Answer:

25. Specific Heat
1. How much heat is needed to raise the temperature of g of water by 85.0°C? Answer: Q = m * c * ∆T = (100.0 g)(4.18 J/g•°C)(85.0°C)
= 35.5 kJ

26. Specific Heat
2. How much heat is absorbed by a 750-g iron skillet when its temperature rises from 25°C to 125°C? Answer:

27. Specific Heat
2. How much heat is absorbed by a 750-g iron skillet when its temperature rises from 25°C to 125°C? Answer: Q = m * c * ∆T = (750 g)(0.449 J/g•°C)(125°C – 25°C)
= (750 g)(0.449 J/g•°C)(100°C)
= 34 kJ

28. Specific Heat
3. In setting up an aquarium, the heater transfers 1200 kJ of heat to 75,000 g of water. What is the increase in the water’s temperature? (Hint: Rearrange the specific heat formula to solve for ∆T.) Answer:

29. Specific Heat
3. In setting up an aquarium, the heater transfers 1200 kJ of heat to 75,000 g of water. What is the increase in the water’s temperature? (Hint: Rearrange the specific heat formula to solve for ∆T.) Answer: ∆T = Q / (m x c) = 1,200,000 J/(75,000 g × 4.18 J/g•°C)
= 3.8°C

30. Specific Heat
4. To release a diamond from its setting, a jeweler heats a 10.0-g silver ring by adding 23.5 J of heat. How much does the temperature of the silver increase? Answer:

31. Specific Heat
4. To release a diamond from its setting, a jeweler heats a 10.0-g silver ring by adding 23.5 J of heat. How much does the temperature of the silver increase? Answer: ∆T = Q / (m x c) = 23.5 J/(10.0 g × J/g•°C)
= 10.0°C

32. Specific Heat
5. What mass of water will change its temperature by 3.0°C when 525 J of heat is added to it? Answer:

33. Specific Heat
5. What mass of water will change its temperature by 3.0°C when 525 J of heat is added to it? Answer: m = Q / (∆T x c) = 525 J/(3.0°C × 4.18 J/g•°C)
= 42 g

34. Specific Heat
On what principle does a calorimeter operate?
A calorimeter is an instrument used to measure changes in thermal energy.
The lower a material’s specific heat, the more its temperature rises when a given amount of energy is absorbed by a given mass.

35. Specific Heat
A calorimeter is used to measure specific heat. A sample is heated and placed in the calorimeter. The temperature change is observed.

36. What is the thermal energy of an object?
Assessment Questions
What is the thermal energy of an object?
the total number of atoms or molecules
the total kinetic energy of the atoms or molecules
the average kinetic energy of the atoms or molecules
the average mechanical energy of the atoms or molecules

37. What is the thermal energy of an object?
Assessment Questions
What is the thermal energy of an object?
the total number of atoms or molecules
the total kinetic energy of the atoms or molecules
the average kinetic energy of the atoms or molecules
the average mechanical energy of the atoms or molecules ANS: B

38. What causes a gas to expand when its temperature is increased?
Assessment Questions
What causes a gas to expand when its temperature is increased?
The number of particles increases as temperature increases.
Each particle expands as its temperature increases, so the total volume increases.
As temperature increases, more electrons leave atoms and move separately.
As gas particles move faster, they overcome some forces of attraction.

39. What causes a gas to expand when its temperature is increased?
Assessment Questions
What causes a gas to expand when its temperature is increased?
The number of particles increases as temperature increases.
Each particle expands as its temperature increases, so the total volume increases.
As temperature increases, more electrons leave atoms and move separately.
As gas particles move faster, they overcome some forces of attraction. ANS: D

40. Assessment Questions
The specific heat of water is 4.18 J/g•°C. How much heat is required to raise the temperature of 1,000 grams of water by 50°C?
83.6 J
83.6 kJ
209 J
209 kJ

41. Assessment Questions
The specific heat of water is 4.18 J/g•°C. How much heat is required to raise the temperature of 1,000 grams of water by 50°C?
83.6 J
83.6 kJ
209 J
209 kJ ANS: D

42. What property of matter can be measured using a calorimeter?
Assessment Questions
What property of matter can be measured using a calorimeter?
temperature
thermal expansion
specific heat
mass

43. What property of matter can be measured using a calorimeter?
Assessment Questions
What property of matter can be measured using a calorimeter?
temperature
thermal expansion
specific heat
mass ANS: C

44. Assessment Questions
Temperature is the transfer of thermal energy from one object to another. True False

45. Assessment Questions
Temperature is the transfer of thermal energy from one object to another. True False
ANS: F, Heat

46. Newton’s cradle helps to visualize conduction
Newton’s cradle helps to visualize conduction. One ball strikes the rest, and most of the kinetic energy is transferred to one ball on the end.

47. Conduction
Why is conduction slower in gases than in liquids or solids?
Conduction is the transfer of thermal energy with no overall transfer of matter.
Conduction in gases is slower than in liquids and solids because the particles in a gas collide less often.

48. Conduction
Conduction occurs within a material or between materials that are touching.
In conduction, collisions between particles transfer thermal energy, without any overall transfer of matter.

49. Conduction
Thermal Conductors
A thermal conductor is a material that conducts thermal energy well.

50. Conduction
The arrows show how thermal energy is conducted away from the heat source in a metal frying pan.

51. Conduction
Metals are good thermal conductors.
When a frying pan is on a hot stove, the bottom of the metal pan heats first and the metal handle last. The flames do not directly heat the handle.
Tile is a better conductor than wood. A tile floor feels colder than a wooden floor when both floors are at room temperature. The tile transfers thermal energy more rapidly away from your skin.

52. Conduction
Thermal Insulators
A material that conducts thermal energy poorly is called a thermal insulator.
Air is a very good insulator. Wool garments and plastic foam cups use trapped air to slow down conduction.

53. Convection
In what natural cycles do convection currents occur?
Convection is the transfer of thermal energy when particles of a fluid move from one place to another.
Convection currents are important in many natural cycles, such as ocean currents, weather systems, and movements of hot rock in Earth’s interior.

54. Convection
Passing sandbags along a line is like transferring thermal energy by convection.
The arrows show convection of air in an oven.

55. Convection
A convection current occurs when a fluid circulates in a loop as it alternately heats up and cools down.
Air at the bottom of an oven heats up, expands, and becomes less dense. The hot air rises.
Rising hot air cools as it moves away from the heat source.
As a result, the coolest air is at the top of the oven.

56. Radiation
How does an object’s temperature affect radiation?
Radiation is the transfer of energy by waves moving through space.
All objects radiate energy. As an object’s temperature increases, the rate at which it radiates energy increases.

57. Radiation
When you stand to the side of a charcoal grill, heat reaches you without convection or conduction.
The sun warms you by radiation on a clear day. The space between the sun and Earth has no air to transfer thermal energy.
Heat lamps used in restaurants are another example of radiation.

58. Radiation
The heating coil on a stove radiates thermal energy.
The changing color of the red arrows indicates that the farther you are from the coil, the less radiation you receive.

59. Thermodynamics
What are the three laws of thermodynamics?

60. Thermodynamics
The study of conversions between thermal energy and other forms of energy is called thermodynamics.
James Prescott Joule ( ) carefully measured the energy changes in a system. Joule's system included a falling weight that turned a paddle wheel in a container of water.
Joule found that the work done by the falling weight almost exactly equaled the thermal energy gained by the water.

61. Thermodynamics
First Law of Thermodynamics
The first law of thermodynamics states that energy is conserved.

62. Thermodynamics
Energy cannot be created or destroyed, but it can be converted into different forms.
Added energy increases the thermal energy of a system or does work on the system. In either case, energy is conserved.

63. Thermodynamics
Pushing on the pump does work on the system.
Some of the work is converted into thermal energy, which heats the air in the pump and the tire.

64. Thermodynamics
Second Law of Thermodynamics
The second law of thermodynamics states that thermal energy can flow from colder objects to hotter objects only if work is done on the system.

65. Thermal energy flows spontaneously only from hotter to colder objects.
Thermodynamics
Thermal energy flows spontaneously only from hotter to colder objects.
A refrigerator must do work to transfer thermal energy from the cold food compartment to the warm room air.
The thermal energy is released by coils at the bottom or in the back of the refrigerator.

66. A heat engine is any device that converts heat into work.
Thermodynamics
A heat engine is any device that converts heat into work.
The efficiency of a heat engine is always less than 100 percent.
Thermal energy that is not converted into work is called waste heat.
Waste heat is lost to the surrounding environment.

67. Thermodynamics
Spontaneous changes will always make a system less orderly, unless work is done on the system.
For example, if you walk long enough, your shoelaces will become untied. But the opposite won't happen; shoelaces don't tie themselves. Disorder in the universe as a whole is always increasing.

68. Thermodynamics
Third Law of Thermodynamics
The third law of thermodynamics states that absolute zero cannot be reached.

69. Thermodynamics
The efficiency of a heat engine increases with a greater difference between the high temperature inside and the cold temperature outside the engine.
A heat engine could be 100 percent efficient if the cold outside environment were at absolute zero (0 Kelvin). This would violate the third law of thermodynamics.

70. Thermodynamics
The third law of thermodynamics states that absolute zero cannot be reached.
This physicist uses a laser to cool rubidium atoms to 3 billionths of a Kelvin above absolute zero.

71. Assessment Questions
What form of energy transfer requires the motion of particles of a fluid?
conduction
convection
radiation
insulation

72. Assessment Questions
What form of energy transfer requires the motion of particles of a fluid?
conduction
convection
radiation
insulation ANS: B

73. What happens in every case in which energy is added to a system?
Assessment Questions
What happens in every case in which energy is added to a system?
Temperature increases.
Work is done on the system.
All of the energy can be accounted for as work or heat.
An identical amount of energy is removed from the system.

74. What happens in every case in which energy is added to a system?
Assessment Questions
What happens in every case in which energy is added to a system?
Temperature increases.
Work is done on the system.
All of the energy can be accounted for as work or heat.
An identical amount of energy is removed from the system. ANS: C

75. Thermal energy can move from a cooler object to a warmer object when
Assessment Questions
Thermal energy can move from a cooler object to a warmer object when
the warmer object is larger.
the cooler object has more thermal energy.
energy is transferred by radiation.
work is done on the system.

76. Thermal energy can move from a cooler object to a warmer object when
Assessment Questions
Thermal energy can move from a cooler object to a warmer object when
the warmer object is larger.
the cooler object has more thermal energy.
energy is transferred by radiation.
work is done on the system. ANS: D

77. According to the third law of thermodynamics, it is impossible
Assessment Questions
According to the third law of thermodynamics, it is impossible
to cool an object to absolute zero.
transfer thermal energy from a cooler object to a warmer object.
convert energy from one form to another.
account for all of the energy in a system.

78. According to the third law of thermodynamics, it is impossible
Assessment Questions
According to the third law of thermodynamics, it is impossible
to cool an object to absolute zero.
transfer thermal energy from a cooler object to a warmer object.
convert energy from one form to another.
account for all of the energy in a system. ANS: A

79. Assessment Questions
All metals are good thermal insulators. True False

80. Assessment Questions
All metals are good thermal insulators. True False
ANS: F, conductors

81. Heat engines played a key role in the development of the modern industrial world. Steam locomotives were an important early use of the steam engine. Electric power plants today use steam turbines.

82. Heat Engines
What are the two main types of heat engines?
The two main types of heat engines are the external combustion engine and the internal combustion engine.

83. External Combustion Engine
Heat Engines
External Combustion Engine
A steam engine is an external combustion engine—an engine that burns fuel outside the engine.
Thomas Newcomen developed the first practical steam engine in 1712 to pump water out of coal mines.
James Watt designed an engine in 1765 that operated at a higher temperature and was more efficient.

84. Heat Engines
When the valve in a steam engine slides, steam is trapped in the cylinder. The steam expands and cools as it pushes the piston to the left.
Hot steam in
Slide valve
Exhaust steam out
Valve rod
Piston rod
Cylinder
Piston

85. Heat Engines
Internal Combustion Engine
An internal combustion engine is a heat engine in which the fuel burns inside the engine.
Most internal combustion engines use pistons that move up and down inside cylinders. Each upward or downward motion of a piston is called a stroke.

86. Heat Engines
Most cars have a four-stroke internal combustion engine. This diagram shows only one of the cylinders during each stroke.
Intake valve
Spark plug
Exhaust valve
Air-fuel mixture
Cylinder
Exhaust gases
Piston
Intake stroke
Compression Stroke
Power stroke
Exhaust stroke

87. Heat Engines
In an internal combustion engine, the cooling system and exhaust transfer heat from the engine to the environment.
Gasoline engines are more efficient than old-fashioned steam engines, but they still are not very efficient. About one third of the energy in a gasoline engine is converted to work.

88. Heating Systems
How do most heating systems distribute thermal energy?
Most heating systems use convection to distribute thermal energy.

89. A central heating system heats many rooms from one central location.
Heating Systems
A central heating system heats many rooms from one central location.
The most commonly used energy sources for central heating systems are electrical energy, natural gas, oil, and coal.
Heating systems differ in how they transfer thermal energy to the rest of the building.

90. Heating Systems
Hot-Water Heating
At the boiler, heating oil or natural gas burns and heats the water.
The circulating pump carries the hot water to radiators in each room.
The hot water transfers thermal energy to the radiator by conduction.

91. Heating Systems
The hot pipes heat the room air by conduction and radiation.
Hot air rises and sets up a convection current in each room.
The cooled water returns to the boiler.

92. Heating Systems
Thermostat
Within the pipes of this hot-water heating system, the water circulates in a convection current. In each room, the air moves in a convection current.
Radiator
Exhaust vent
Expansion tank
Boiler
Circulating pump

93. Heating Systems Steam Heating
Steam heating is very similar to hot-water heating except that steam is used instead of hot water.
The transfer of heat from the steam-heated radiator to the room still occurs by conduction and radiation.
Steam heating often is used in older buildings or when many buildings are heated from one central location.

94. Electric Baseboard Heating
Heating Systems
Electric Baseboard Heating
An electric baseboard heater uses electrical energy to heat a room.
A conductor is used to convert electrical energy to thermal energy.
The hot coil heats the air near it by conduction and radiation.
Convection circulates the warm air to heat the room.

95. Heating Systems Forced-Air Heating
Forced-air heating systems use fans to circulate warm air through ducts to the rooms of a building.
Convection circulates air in each room.
Warm air entering the room rises toward the ceiling.
Cool room air returns to the furnace through floor vents on the other side of the room.

96. Heating Systems
Hot air enters the room through a supply vent in the floor. The hot air rises as cooler, denser air in the room sinks.
Hot air rises
Cool air sinks
Supply vent
Return vent
Chimney
Duct
Furnace

97. Cooling Systems
How does a heat pump reverse the normal flow of heat?
A heat pump is a device that reverses the normal flow of thermal energy.
Heat pumps must do work on a refrigerant in order to reverse the normal flow of thermal energy.

98. Cooling Systems
A refrigerant is a fluid that vaporizes and condenses inside the tubing of a heat pump.
When the refrigerant absorbs heat, it vaporizes, or turns into a gas.
When the refrigerant gives off heat, it condenses, or turns back into a liquid.

99. Cooling Systems Refrigerators
A refrigerator is a heat pump—it transfers thermal energy from the cold food compartment to the warm room.
A motor must do work to move refrigerant through tubing inside the refrigerator walls.
Coils of tubing underneath or behind the refrigerator release heat absorbed from the food compartment and thermal energy produced by the work the motor does.

100. Cooling Systems
When a refrigerator door is open, some thermal energy from the room enters the refrigerator. More thermal energy leaves the refrigerator through the coils.
Temperature in room: 25°C
Temperature in refrigerator: 3°C

101. Cooling Systems
Air Conditioners
The compressor in a room air conditioner raises the temperature and pressure of the refrigerant, turning it into a hot, high-pressure gas.
The condenser coil is hotter than the outside air, so heat flows spontaneously to the outside air.
The refrigerant cools and condenses into a liquid.

102. Cooling Systems
The liquid refrigerant then flows through the expansion valve and decreases in temperature.
As the cold refrigerant flows through the evaporator coil, it absorbs thermal energy from the warm room air.
The fan sends cold air back into the room. The refrigerant becomes a vapor, and the process starts all over again.

103. Cooling Systems
In a window air conditioner, outside air is heated as a fan blows it through the condenser coil.
Condenser coil Vapor cools to liquid as heat is removed.
Warm air out
Cold air out
Compressor
Expansion valve Pressure drops, causing liquid refrigerant to become cold.
Warm air in
Evaporator coil Liquid absorbs heat to become vapor.

104. What Is the Real Cost of a Washing Machine?
If you ever shop for a new washing machine, you’ll notice the bright yellow Energy Guide sticker on each machine. The sticker gives the machine’s operating cost per year as estimated by the U.S. Department of Energy. The largest part of the cost for cleaning clothes is heating the water that goes into the washing machine. So a machine that uses less water is more efficient.

105. What Is the Real Cost of a Washing Machine?
Using Graphs One family uses an electric water heater. What is their cost per year for machine A? For machine D?

106. What Is the Real Cost of a Washing Machine?
Using Graphs One family uses an electric water heater. What is their cost per year for machine A? For machine D? Answer: The annual cost of Brand A is about $10 per year. The annual cost of Brand D is about $60 per year.

107. What Is the Real Cost of a Washing Machine?
Calculating One family uses an electric water heater. What is their cost per year for machine A? For machine D? Answer:

108. What Is the Real Cost of a Washing Machine?
Calculating One family uses an electric water heater. What is their cost per year for machine A? For machine D? Answer: The family saves $50 each year using Brand A.

109. Answer: What Is the Real Cost of a Washing Machine?
Calculating The price of machine A is $300 more than the price of machine D. If the family uses a machine for 10 years, which one costs less overall? (Hint: Add the price to the operating cost for 10 years.)
Answer:

110. What Is the Real Cost of a Washing Machine?
Calculating The price of machine A is $300 more than the price of machine D. If the family uses a machine for 10 years, which one costs less overall? (Hint: Add the price to the operating cost for 10 years.)
Answer: The operation cost of Brand A for 10 years is 10 × $10 = $100. The operation cost of Brand D for 10 years is 10 × $60 = $600. Brand A costs less overall because although the initial price is $300 higher, the machine saves $500 in operating costs.

111. What Is the Real Cost of a Washing Machine?
Calculating Another family uses a gas water heater. Which machine should this family choose? Explain your thinking Answer:

112. What Is the Real Cost of a Washing Machine?
Calculating Another family uses a gas water heater. Which machine should this family choose? Explain your thinking Answer: Using a gas water heater, Brand A saves only $20 in operating costs each year. Based only on cost, the family should choose Brand D because it will cost $100 less to own and operate for 10 years.

113. What Is the Real Cost of a Washing Machine?
Evaluating and Revising A washing machine advertisement states that the annual cost assumes an electric water heater is used. Why would an advertisement include only this cost?

114. What Is the Real Cost of a Washing Machine?
Evaluating and Revising A washing machine advertisement states that the annual cost assumes an electric water heater is used. Why would an advertisement include only this cost? Answer: The goal of the advertisement is to convince as many people as possible to buy the machine. Therefore, the advertisement emphasizes the money that could be saved under the best of circumstances (using an electric water heater).

115. Assessment Questions
Only about one-third of the energy in gasoline is converted to work in an internal combustion engine. The rest of the chemical energy is
lost as unused mechanical energy.
destroyed by the engine.
converted to potential energy.
discharged as waste heat.

116. Assessment Questions
Only about one-third of the energy in gasoline is converted to work in an internal combustion engine. The rest of the chemical energy is
lost as unused mechanical energy.
destroyed by the engine.
converted to potential energy.
discharged as waste heat. ANS: D

117. How is a room heated by an electric baseboard heating system?
Assessment Questions
How is a room heated by an electric baseboard heating system?
conduction and convection only
conduction and radiation only
convection and radiation only
conduction, convection, and radiation

118. How is a room heated by an electric baseboard heating system?
Assessment Questions
How is a room heated by an electric baseboard heating system?
conduction and convection only
conduction and radiation only
convection and radiation only
conduction, convection, and radiation ANS: C

119. How do air conditioners reverse the normal flow of heat?
Assessment Questions
How do air conditioners reverse the normal flow of heat?
moving cool air from outside to inside the house separating warm atoms from cool atoms vaporizing and condensing a refrigerant blowing the warm air away with a fan

120. How do air conditioners reverse the normal flow of heat?
Assessment Questions
How do air conditioners reverse the normal flow of heat?
moving cool air from outside to inside the house separating warm atoms from cool atoms vaporizing and condensing a refrigerant blowing the warm air away with a fan ANS: C

121. Assessment Questions
Forced air heating systems are often used to heat many buildings from a central location. True False

122. Assessment Questions
Forced air heating systems are often used to heat many buildings from a central location. True False
ANS: F, Steam