CVHS The Lowest Temperature Ever Recorded on Earth Worksheet

1
General Science 1B
Credit 4
Rev. 5/5/21
NAME:_________________________
CREDIT 4B: HEAT, WORK, AND ENERGY
Learning Goal for this Credit
Design an investigation or model using appropriate scientific tools, resources and methods.
Lesson
Title
INTRODUCTION
4.1
Heat
4.2
The First Law of Thermodynamics
4.3
The Second Law of Thermodynamics
PERFORMANCE TASK
QUIZ
Assignments

 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Heat and Temperature
 Review Questions
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Thermodynamics Concept Map
 Review Questions
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Energy Education: Heat Engines
 Review Questions


Student Support Icons
Title
Icon
Description
Review
Activity
This provides the students with a reminder that they need to answer questions.
Technology
Guides students through the tasks and assignments that require the use of
technology and manipulatives.
Reading
This icon lets the students know they will be completing a reading activity.
Credit Materials



Materials
Pen/Pencil
HMH Physics Textbook
(optional)
Packet



Technology Needs
Internet
Computer
HMH Online Resources
(optional)
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General Science 1B
Credit 4
NAME:_________________________
CREDIT 4B: INTRODUCTION
Read “How Do Hot Air Balloons Fly?” and watch the video “Felix Baumgartner’s Supersonic Freefall from
128k’ – Mission Highlights” below. Then answer the essential question.
How Do Hot Air Balloons Fly?
What happens to an ice cube when you put it in a glass of room temperature
water? As the temperature of the water decreases, the temperature of the ice
increases, until both are the same temperature. The energy transferred to
equalize the temperature is defined as heat. Even though the water may have
cooled, the heat melted the ice cube. This energy transferred as heat can be
used to do work. Work is a measure of the energy transfer that occurs when
an object is moved over a distance by an external force.
For example, look at the picture of a hot air balloon to the right. The balloon
is filled with hot air so that the air inside the balloon has a higher temperature
than the air outside of the balloon. The difference in temperature causes
energy transfers between the gas inside of the balloon and the air outside.
This transfer of energy as heat is used to do work by lifting the balloon,
causing it to rise into the air!
An essential question is something that allows you to explore what the credit is about. Before you answer the
question, examine the picture. Watch the video if you feel you need more information. Then, answer the
essential question to the best of your ability. You will revisit it at the end of the credit to see if your answer has
evolved.
Felix Baumgartner’s Supersonic Freefall from 128k’ – Mission Highlights (1:30)

“Felix Baumgartner’s Supersonic Freefall from 128k’ – Mission Highlights.” YouTube. Red Bull, 4 Oct. 2012. Web. 26 Jan. 2016.
Essential Question
If a balloon uses heat as energy to rise, how do you think it is able to come back down to the ground? Where
does the energy go?
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3
General Science 1B
Credit 4
LESSON 4.1: HEAT
Learning Goal for this Credit
Design an investigation or model using appropriate scientific tools, resources and methods.
Learning Goals for this Lesson
 Relate temperature to the kinetic energy of atoms and molecules.
 Describe the changes in the temperatures of two objects reaching thermal equilibrium.
 Identify the three temperature scales and convert from one scale to another.
 Explain heat as the energy transferred between substances that are at different temperatures.
Lesson Assignments
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Animated Physics: Heat
 Review Questions
Engage
Connect to Prior Knowledge
What are some ways in which the temperature of a substance can be measured?
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4
General Science 1B
Credit 4
Explore
Exploration Activity
The outdoor temperature range from region to region can vary greatly. In Death Valley, California temperatures
can regularly reach 120 degrees Fahrenheit (o F) during the summer. The unit most used in the United States to
measure temperature is the Fahrenheit (o F) scale. In other countries the Celsius (o C) scale is used to measure
temperature. In Antarctica, over the elevated inland, temperatures can drop below -80 degrees Celsius (o C)
during the winter. Even though there are different units used to measure temperature, these units of Fahrenheit
and Celsius can be converted to each other using the following equation.
𝟗
𝑻𝑭 = 𝑻𝑪 + 𝟑𝟐. 𝟎
𝟓
TF = Temperature in degrees Fahrenheit
TC = Temperature in degrees Celsius
Formula for
converting F and C
In this equation TF represents the temperature in degrees Fahrenheit (o F) and TC represents the temperature in
degrees Celsius (o C). The 32.0 represents the difference on each scale where water freezes. On the Celsius
scale water freezes at 0.0 degrees and on the Fahrenheit scale water freezes at 32.0 degrees.
Example:
The average human body temperature is 37oC. What is the equivalent temperature on the Fahrenheit scale?
Step 1: Write out the equation where x represents the unknown temperature we are trying to find. In this
problem we know the temperature in oC and the unknown is the temperature in oF.
𝟗
𝒙 = ( ) × (𝟑𝟕) + 𝟑𝟐
𝟓
Step 2: Using order of operation, begin solving for x. First divide the fraction in the parenthesis.
𝒙 = (𝟏. 𝟖) × (𝟑𝟕) + 𝟑𝟐
Step 3: Then multiply.
𝒙 = 𝟔𝟔. 𝟔 + 𝟑𝟐
Step 4: Then add.
𝒙 = 𝟗𝟖. 𝟔
The average body temperature in degrees Fahrenheit equals 98.6 oF.
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General Science 1B
Credit 4
Another unit that is used to measure temperature is Kelvin (K). A temperature difference of one degree is the
same on the Kelvin and the Celsius scales. The two scales only differ in the choice of the zero point. On the
Kelvin scale, absolute zero is 0oKelvin, and is the temperature that is the lowest possible. On the Celsius scale
absolute zero is represented by the temperature -273.15oC. The equation below is used to convert between the
units Celsius and Kelvin.
𝑻 = 𝑻𝑪 + 𝟐𝟕𝟑. 𝟏𝟓
T = Temperature in degrees Kelvin
TC = Temperature in degrees Celsius
Formula for converting K
and C
In this equation T represents temperature in Kelvin and TC represents the temperature in degrees Celsius (oC).
The 273.15 represents the difference in the zero point.
Example:
Water boils at approximately 100oC. What is the boiling point of water on the Kelvin Scale?
Step 1: Write out the equation where x represents the unknown temperature we are trying to find. In this
problem we know the temperature in oC and the unknown is the temperature in K.
𝒙 = 𝟏𝟎𝟎 + 𝟐𝟕𝟑. 𝟏𝟓
Step 2: Using addition, solve for x.
𝒙 = 𝟑𝟕𝟑. 𝟏𝟓
The boiling point of water on the Kelvin scale is equal to 373.15 K.
Using the equations and examples, answer the following questions. Make sure to show your work.
1. On the Fahrenheit scale, water freezes at 32oF.
a. What is the equivalent temperature on the Celsius scale?
b. Now that you know the temperature equivalent on the Celsius scale, what is the equivalent on
the Kelvin scale?
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General Science 1B
Credit 4
2. Dry ice, which is the solid form of carbon dioxide (CO2), has a very low temperature of -78.5oC.
a. What is the temperature of dry ice expressed on the Kelvin scale?
b. What is the temperature of dry ice expressed on the Fahrenheit scale?
3. The lowest temperature ever recorded on Earth is -128.6oF, recorded in Antarctica in 1983.
a. What is this temperature on the Celsius scale?
b. Now that you know the temperature on the Celsius scale, what is the equivalent on the Kelvin
scale?
7
General Science 1B
Credit 4
Explain
As you complete the reading, answer the questions in the space provided.
Reading
What is Heat?
Temperature is the quantity that tells us how hot or cold a substance is. Temperature can be measured on a
thermometer using either the Fahrenheit, Celsius, or Kelvin scales. Temperature is the measure of the average
kinetic energy of the particles in a substance. Recall that kinetic energy is the energy of motion. When a
substances temperature rises, the molecules move faster, increasing the substances kinetic energy.
When you touch a hot pan on the stove, energy is transferred to your hand from the pan because the pan is
hotter than your hand. If you touch a piece of ice, energy will enter the ice from your hand because the ice is
colder than your hand. The direction of energy transfer is always from hotter to colder. This energy transfer that
takes place because of temperature differences is known as heat. Matter contains energy in various forms, but
does not contain heat. Heat is energy moving from a hotter substance to a colder substance. Once heat is
transferred, and the substances in contact with each other reach the same temperature, we say the objects are in
thermal equilibrium. At this point the energy ceases to be heat. For example, when ice is added to a hot cup of
water, energy in the form of heat transfers from hot water to the ice. The water decreases in temperature as it
loses energy, and the ice increases in temperature as it gains energy. Once the ice is melted and the ice/water
mixture has a stable temperature, it has reached thermal equilibrium.
1. Why is it incorrect to say matter contains heat?
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2. What is thermal equilibrium?
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How is Heat Transferred?
Heat can be transferred by conduction, convection, and radiation. If you walk on a cold tile floor barefoot you
will feel the cold on your warm feet. Heat is transferring through your feet to the tile floor by conduction.
Conduction of heat takes place when energy is transferred from one substance to another when the substances
are in direct contact. In electricity, the flow of a charge through a wire is also an example of conduction.
On a cold day, a fireplace may be used to warm the air in our homes. This warm air travels upward to displace
the cooler air in the room. This movement of heat through the air is known as convection. Convection can take
place in a gas or a liquid. Whether we heat water in a pot or heat the air in a room, the process is the same.
8
General Science 1B
Credit 4
Recall that convection currents take place within Earth’s interior causing the movement of Earth’s tectonic
plates.
Heat from the sun warms Earth’s surface. It passes through space and Earth’s atmosphere in the form of radiant
energy. This is an example of radiation. Radiation is the transfer of energy by electromagnetic waves.
Electromagnetic waves include radio waves, microwaves, infrared, visible light, ultraviolet light, x-rays, and
gamma rays. When a fireplace is heating a room, the majority of the heat goes up the chimney by convection,
but that heat that warms a person sitting near the fire comes to them by radiation, mainly from infrared waves.
Conduction
Convection
Radiation
3. How does conduction occur?
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4. How is a fireplace an example of both convection and radiation?
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5. Give one example for each form of heat transfer (conduction, convection, radiation).
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Adapted from Hewitt, Paul G. “Chapter 21: Temperature, Heat, and Expansion/Chapter 22: Heat Transfer.” Conceptual Physics: the High School Physics Program,
Pearson/Prentice Hall, 2006, pp. 307–336.
9
General Science 1B
Credit 4
Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
Thermal Equilibrium (3:47)

“Thermal Equlibrium” YouTube. Bozeman Science, 26 Jul. 2015. Web. 29 Apr. 2021.
How does heat move between two objects of different temperatures? This video will
explain how thermal equilibrium is obtained within a system.
Converting Between Temperature Scales (6:17)

“Converting Between Temperature Scales (Celsius, Fahrenheit, and Kelvin)” YouTube. Professor Dave Explains, 3 Jul. 2017.
Web. 29 Apr. 2021.
How is temperature converted between the different units of Celsius, Fahrenheit, and
Kelvin? This video will explain the temperature conversion process.
Misconceptions About Temperature (3:59)

“Misconceptions About Temperature.” YouTube. Veritasium, 24 Aug. 2012. Web. 15 Feb. 2016.
When you touch something do you feel its temperature? This video will
explain how heat transfer and conductivity are related to perceived temperature.
10
General Science 1B
Credit 4
Elaborate
Heat and Temperature
The following video examines what heat is at a molecular level. Follow the link below to watch it, then answer
the questions.
Heat and Temperature

“Heat and Temperature.” YouTube, Professor Dave Explains, 23 Mar. 2017.
1. What is heat?
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2. How is the mass and speed of a particle related to its kinetic energy?
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3. How is kinetic energy related to temperature?
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4. How are temperature and heat related?
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11
General Science 1B
Credit 4
Evaluate
Review Questions
Answer the following questions.
1. In what direction does heat flow between two objects of different temperatures?
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2. If you leave a cup of hot chocolate sitting on a table what eventually happens to the temperature? Does
the temperature ever reach a thermal equilibrium?
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3. In what three ways can energy be transferred as heat?
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4. Ultraviolet light is the cause of sunburns. What type of heat transfer has occurred when a person gets a
sunburn from ultraviolet light?
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12
General Science 1B
Credit 4
LESSON 4.2: THE FIRST LAW OF
THERMODYNAMICS
Learning Goal for this Credit
Design an investigation or model using appropriate scientific tools, resources and methods.
Learning Goals for this Lesson
 Illustrate how the first law of thermodynamics is a statement of energy conservation.
 Describe absolute zero and how it relates to the internal energy of a system.
 Explain changes in heat, work, and internal energy by applying the first law of thermodynamics.
Lesson Assignments
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Thermodynamics Concept Map
 Review Questions
Engage
Connect to Prior Knowledge
Give an example in which energy as heat is used to perform a task.
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13
General Science 1B
Credit 4
Explore
Exploration Activity
Thermodynamics is the study of heat and its transformation to energy.
Recall that heat is a form of energy transfer between substances of
different temperatures, and energy is a property of an object or system that
enables it to do work. When heat is added to a system, it transforms to an
equal amount of some other form of energy. A system is a portion of the
physical universe chosen for analysis. Everything outside of the system is
known as the environment. The first law of thermodynamics states that
energy can neither be created nor destroyed. It can only change forms. In
any process, total energy remains the same. For thermodynamic systems,
the heat supplied to the system can be used to do work. The internal
energy of a system can be changed by transferring energy from the
environment into or out of the system as work, heat, or both.
1. Rub your hands together as quickly as you can. What did you observe?
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2. The work you did on your skin is converted to thermal energy. Rub your hands together again. Now
place them on your face. What do you feel on your face?
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3. The thermal energy is transferred from your hands to your face in the form of heat. Work and heat are
interchangeable. What might be an example where you add heat to something to do work? (Hint: reread
the Introduction on page 3 of this credit)
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General Science 1B
Credit 4
Explain
As you complete the reading, answer the questions in the space provided.
Reading
What is Absolute Zero?
As the motion of atoms in a substance increases, temperature also increases. In contrast, as motion of atoms in
a substance decreases, temperature will decrease. As the motion of these atoms approaches zero, the
temperature of the substance approaches its lower limit. The lower limit of temperature is known as absolute
zero. At absolute zero, no further lowering of a substances temperature can occur, and no more energy can be
extracted from the substance. Absolute zero corresponds to zero degrees on the Kelvin scale or -273 degrees on
the Celsius scale.
1. Can the temperature of a substance go below absolute zero? Explain your answer.
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What is the First Law of Thermodynamics?
The first law of thermodynamics states that energy can neither be created nor destroyed. It can only change
forms. When this is applied to thermodynamic systems, it means that whenever heat is added to a system it
transforms to an equal amount of another form of energy. A system can be as small as a group of atoms, or as
large as the universe. A car engine, planet Earth, or even your body can be considered a system. If we add
energy to a system in the form of heat it can do one or both of two things:


Increase the internal energy of the system if it remains in the system.
Do work on the environment if it leaves the system.
So, the first law of thermodynamics can be summed up as:
Heat added = Increase in internal energy + External work done by the system
For example, as heat is added to a hot air balloon, it does work causing
the balloon to rise into the air. The balloon is a thermodynamic system.
The added heat increases the internal energy, causing the air inside the
system to be hotter than the air of the surrounding environment. Work
is done as the balloon rises. If the heat is no longer added to the
balloon, eventually the air temperature inside of the balloon with lower
back down to the temperature of the air in the surrounding environment
to achieve thermal equilibrium. Work will no longer be done, and the
balloon will descend to the ground.
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General Science 1B
Credit 4
2. Explain the first law of thermodynamics.
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3. If energy is added to a system in the form of heat, what two things can occur?
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4. What is an example of a system? What would be the external environment for this system?
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Adapted from Hewitt, Paul G. Conceptual Physics. Upper Saddle River, NJ: Prentice Hall, 2006. Print.
Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
What is Absolute Zero Temperature? (2:27)

“What Is Absolute Zero Temperature.” YouTube, Pocket Science, 7 Nov. 2014.
What is absolute zero? This video explains how cold absolute zero actually is and the
temperature readings of absolute zero on the Kelvin and Celsius scales.
What is the First Law of Thermodynamics? (4:08)

TheRoyalInstitution. “What Is the First Law of Thermodynamics?” YouTube, YouTube, 5 Dec. 2016.
What is the first law of thermodynamics? This video will explain the first law of
thermodynamics as well as how heat can be used to do work.
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General Science 1B
Credit 4
Elaborate
Thermodynamics Concept Map
Complete the concept map below to explain the first law of thermodynamics. Each term can be found in the
reading section from this lesson.
Work
System
Energy
Heat
Environment
Thermodynamics
Internal Energy
Serway, Raymond A., and Jerry S. Faughn. “Chapter 10: Thermodynamics/Concept Map: Thermodynamics.” Holt McDougal Physics, Holt McDougal, a Division of
Houghton Mifflin Harcourt Publishing Co., 2012.
Evaluate
Review Questions
Answer the following questions.
1. What is the lowest possible temperature on the Celsius scale? On the Kelvin scale?
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2. If heat is added to a system, what happens to the internal energy?
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3. If external work is done on the environment by a system, what happens to the internal energy?
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General Science 1B
Credit 4
LESSON 4.3: THE SECOND LAW OF
THERMODYNAMICS
Learning Goal for this Credit
Design an investigation or model using appropriate scientific tools, resources and methods.
Learning Goals for this Lesson
 Recognize why the second law of thermodynamics requires two bodies at different temperatures for
work to be done.
 Relate the disorder of a system to its ability to do work or transfer energy as heat.
Lesson Assignments
 Connect to Prior Knowledge
 Exploration Activity
 Reading and Questions
 Videos (optional)
 Energy Education: Heat Engines
 Review Questions
Engage
Connect to Prior Knowledge
Give an example of a process where heat flows from a warmer object to a colder object.
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General Science 1B
Credit 4
Explore
Exploration Activity
It is easy to change work completely into heat. You
did this in the last lesson by rubbing your hands
together. The reverse process of changing heat
completely into work is something that cannot be done.
Some heat can be converted to work, but the rest is
always lost. A heat engine is a device that converts
internal energy into work. Internal energy is increased
by the addition of heat. The first heat engine, the steam
engine, was invented in the 1700s.
Today, a type of steam engine called a steam turbine is
used to produce most of the electricity for the United
States. In the example to the right, water is heated in a
high-pressure boiler. The water evaporates and
becomes steam. The steam travels through a chamber
to a turbine. The turbine spins when the highly pressurized steam pushes the blades. The turbine is connected to
an external generator that collects mechanical energy as electricity. The steam is cooled once it passes through
the turbine and becomes water again. A pump takes the water back up to the boiler to start the process over. In
this steam turbine heat is used to do mechanical work, but not all of the heat gets converted to work. Some is
lost to friction and the outside environment. Recall that friction is a force that resists motion of objects that are
in contact with each other.
1. What is a heat engine?
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2. What are steam turbines used to produce?
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3. Some of the heat of the steam turbine is converted into mechanical work. What happens to the rest of the
heat that is not converted to work?
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Adapted from Hewitt, Paul G. “Chapter 24: Thermodynamics/Section 24.5: Heat Engines and the Second Law”. Conceptual Physics: the High School Physics Program,
Pearson/Prentice Hall, 2006, pp. 361-362.
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General Science 1B
Credit 4
Explain
As you complete the reading, answer the questions in the space provided.
Reading
What is the Second Law of Thermodynamics?
The second law of thermodynamics states that heat will never of itself flow from a colder object to a hotter
object. This means that the direction of heat flow is from hot to cold unless work is added to the system. Heat
can be made to flow the other way, but only by adding work from an external source. For example, a
refrigerator’s electric motor acts as an external source to reverse heat flow and keep your food cold.
It is easy to change work completely into heat; simply rub your
hands together or push a crate at constant speed across a floor. The
work you do in overcoming friction is completely converted to heat,
but the reverse process of changing heat entirely to work cannot
occur. The second law of thermodynamics also explains that no
cyclic process that converts heat entirely to work is possible. The
best than can be done is the conversion of some heat to mechanical
work. This process is what powers gasoline driven automobiles.
A heat engine is a device that changes internal energy into
mechanical work. The basic idea behind a heat engine is that
mechanical work can be obtained only when heat flows from a high
temperature to a low temperature. In every heat engine only some
of the heat can be transformed into work. No heat engine can
transfer all its absorbed energy to work. The measure of how well a
heat engine operates is called the engine’s efficiency. Efficiency
measures the useful energy taken out of a process relative to the
total energy put into a process. The higher the percentage, the more
efficient the heat engine.
1. Explain the second law of thermodynamics.
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2. What is a heat engine?
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3. What is efficiency a measure of for a heat engine?
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What is Entropy?
Recall that the first law of thermodynamics states that energy can be neither created nor destroyed, it can only
change forms. The second law of thermodynamics adds that heat transfers from hot to cold substances. Work
can be done by this heat flow which causes an increase of internal energy, but not all the heat can be converted
to work. The wasted heat is unavailable or lost. Another way to say this is that some of the available (ordered
energy) becomes unavailable (disordered energy). The idea of ordered energy tending to disordered energy is
the concept of entropy. Entropy is a measure of disorder within a system. In natural systems, over time, entropy
always increases and the available energy of the system for doing work decreases. However, if work is added to
the system, it can decrease the entropy. For example, all living organisms input work to decrease entropy. They
take in energy from the surrounding environment and use it to do work inside their bodies to decrease disorder.
This energy transformation is what supports life. But as with all living organisms, eventually this energy intake
and transformation slows, and then stops. The organism soon dies and tends to disorder as it decomposes.
4. What is entropy a measure of?
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5. How would entropy relate to the efficiency of a heat engine?
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Adapted from Hewitt, Paul G. Conceptual Physics. Upper Saddle River, NJ: Prentice Hall, 2006. Print.
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General Science 1B
Credit 4
Videos
If you would like to learn more about this topic, watch the videos below for more information. (Optional)
What is Entropy (5:19)

“What is entropy?.” YouTube. TED-Ed, 9 May. 2017. Web. 29 Apr 2021.
What is entropy? This video will explain entropy and give examples of
entropy found in everyday objects.
The Rubber Band Heat Engine (5:46)

“The Rubber Band Heat Engine.” YouTube. Adam Micolich, 5 Sept. 2008. Web. 04 June 2014.
How can a rubber band be used to create a heat engine? This video will show you how
even a simple heat engine can be used to do work.
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General Science 1B
Credit 4
Elaborate
Energy Education: Heat Engines
Read the following information on heat engines and then answer the questions.
Heat Engine
A heat engine is a device (like the motor in a car) that produces motion from heat. When people rub their hands
together friction turns mechanical energy (the motion of our hands) into thermal energy (the hands get warmer).
Heat engines do just the opposite; they take the energy from being warm (compared to the surroundings) and
turn that into motion. Often this motion is turned into electricity with a generator.
Almost all of the energy that is harnessed for transportation and electricity comes from heat engines. Hot
objects, even gases, have thermal energy that can be turned into something useful. Heat engines move energy
from a hot place to a cold place and divert some of that energy into mechanical energy. Heat engines require a
difference in temperature to function.
The study of thermodynamics was initially inspired by trying to get as much energy out of heat engines as
possible. To this day, various fuels are used, like gasoline, coal, and uranium. All of these heat engines still
operate under the limits imposed by the second law of thermodynamics. This means that various fuels are used
to heat a gas and a large cold reservoir is needed in order to get rid of waste heat. Often, the waste heat goes into
the atmosphere or a large body of water (the ocean, a lake, or a river).
Depending on the type of engine, different processes are employed, like igniting fuel through combustion
(gasoline and coal), or using energy from nuclear processes to produce heat (uranium), but the end goal is the
same: to turn the heat into work. The most familiar example of a heat engine is the engine of a car, but most
power plants, like coal, natural gas, and nuclear, are also heat engines.
Internal Combustion Engine
Internal combustion engines are the most common form of heat engines, as they are used in vehicles, boats,
ships, airplanes, and trains. They are named as such because the fuel is ignited in order to do work inside the
engine. The same fuel and air mixture is then emitted as exhaust. While this is most commonly done using a
piston, it can also be done with a turbine. The picture below is an example of an internal combustion engine.
This particular type is
called a four stroke
engine, which is quite
common in cars.
External Heat Engine
External heat engines are
generally steam engines,
and they differ from
internal ones in that the
heat source is separate
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from the gas that does work. These heat engines are usually called external combustion engines because
combustion is occurring outside of the engine. For example, external combustion would be using a flame to heat
water into steam, then using the steam to turn a turbine. This is different from internal combustion, like in a car
engine, where the gasoline ignites inside a piston, does work, and then is expelled. Nuclear reactors don’t have
combustion, so the broader term external heat engine is used. The boiling water reactor is an external heat
engine, as are other nuclear power plants.
Cogeneration
A heat engine has two byproducts: work and heat. The purpose of most engines is to produce work, and the heat
is treated simply as waste. Cogeneration is using the waste heat for useful things. The heater in a car works
using cogeneration – taking waste heat from the engine to heat air which warms up the cabin. This is why
running a car’s heater in winter has little effect on gas mileage, but running air conditioning in the summertime
can cost an estimated 10-20% of a car’s gas mileage.
1. What are some of the types of fuels that are used in heat engines?
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2. Where is the “waste heat” generally disposed of from a heat engine?
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3. What type of things are internal combustion heat engines used in?
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4. How does an external heat engine differ from an internal heat engine?
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5. Nuclear reactors do not have combustion, so how is heat supplied to do work?
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6. Explain cogeneration.
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Campbell, Allison, Fatima Garcia, Jordan Hanania, James Jenden, and Jason Donev. “Heat Engine.” – Energy Education. University of Calgary, n.d. Web. 18 Feb. 2016.
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Evaluate
Review Questions
Answer the following questions.
1. How does the second law of thermodynamics relate to the direction of heat flow?
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2. Would a heat engine be more efficient in an environment that generally has warm or cold temperatures?
Explain your answer.
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3. What must be added to a system to decrease entropy?
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Revisit the essential question. Did your answer change? Why or why not?
Essential Question
If a balloon uses heat as energy to rise, how do you think it is able to come back down to the ground? Where
does the energy go?
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