SAM Teachers Guide Heat and Temperature Overview Students learn that temperature measures average kinetic energy, and heat is the transfer of energy from hot systems to cold systems. They consider what makes a good conductor. Learning Objectives Students will be able to: • Distinguish between heat and temperature at the atomic level. • Determine temperature is related to both the speed and the mass of atoms. • Explain that temperature is a measure of the average kinetic energy of atoms and molecules in a system. • Experiment with the amount of energy and the size of a system and its relationship to a rise in temperature. • Compare thermal radiation and heat conduction. Possible Student Pre/Misconceptions • Heat and temperature are the same thing. • Heat is a form of energy. • Heat is a physical substance, such as steam. • Heating a substance increases the motion of atoms only. Models to Highlight and Possible Discussion Questions After completion of Part 1 of the activity: Models to Highlight: • Page 2 – Bottom Model o Use this model to highlight the ways in which the mass of atoms and temperature of the system is related to the motion of the atoms. o Link to other SAM activities: Atoms and Energy. Review the concepts of heat increasing the energy in a system. • Page 4 – Equilibrium Model o Use this model to discuss the difference in the system from when the divider is present (for the first few seconds) and when the divider is removed. Discuss what happens to the temperature of the two containers once the separator is removed. o Link to other SAM activities: Atoms and Energy. Review the concepts of energy transfer. Possible Discussion Questions: • What is the difference between heat and temperature? • How does the kinetic energy of a substance depend on temperature and mass? Hint: Refer to the equation KE = ½ mv2 • Have students share real‑world examples of systems reaching equilibrium and / or of substances that start out at different temperatures and end up the same temperature over time. Ask students to describe what is happening at the atomic level. After completion of Part 2 of the activity: Models to Highlight: • Page 6 – Heat Conduction o Take this opportunity to discuss the different shape of the conductors and their properties. Analyze the effect of the type of conductor used on the time it takes the two materials to reach a temperature equilibrium. • Page 8 – Thermal Radiation o Use this model to discuss the presence of photons emitted from vibrational energy and the difference between this and atom‑to‑
atom contact. o Link to other SAM activities: Energetic States and Photons. Use this to preview the idea of quantized energy levels and photons. Possible Discussion Questions: • What properties of a conductor will determine how effective it is at heat transfer? Have students share some examples of very efficient and inefficient conductors. Students can share ideas about why different materials could be used for varied purposes. • Have students brainstorm examples of heat transfer and thermal radiation focusing on how they are different. Connections to Other SAM Activities This activity helps students learn that temperature is the average kinetic energy of atoms whereas heat is the transfer of energy from hot systems to cold systems. Atoms and Energy supports this activity. Students learn what kinetic energy is and how energy is transferred between kinetic and potential forms. Heat and Temperature addresses the concept that atoms are in constant motion due to thermal energy. This is evident in almost all of the other SAM activities. However, there are some key lessons where this point is particularly highlighted. In Electricity, an electric current heating a filament causes a light bulb to glow. Understanding heat is essential to understanding this model. In Excited States and Photons, kinetic energy is converted into the excited states of atoms and is released in the form of a photon. Phase Change explores what happens to substance as heat is added and/or removed. The Gas Laws activity explores the relationships between pressure, volume, and temperature within gases. Intermolecular Attractions are illustrated by how tightly or loosely atoms are attracted to one another. This is demonstrated by using heat to break bonds between different atoms. For solids, the amount of solute that can dissolve in a given solvent increases as the temperature is raised, and is shown in Solubility. When analyzing chemical reactions in Chemical Reactions and Stoichiometry, it is evident that increases in temperature usually increase the reaction rate due to more frequent atomic collisions. In Chemical Reactions and Energy, an understanding of heat and temperature is necessary to analyze endothermic and exothermic reactions. Finally, in Four Levels of Protein Structure, the binding strength (strength of attraction) between proteins (or a protein – ligand) is based on the ability they have to stay together given thermal motion. Activity Answer Guide Page 1: 1. Compare the motion of the air molecules
at high and low temperatures.
4. How is the average KE affected by adding
or subtracting heat?
The air molecules move faster at higher
temperatures and slower at lower temperatures.
Adding heat increases the average KE because
the particles are moving faster and colliding
more often. Subtracting heat lowers the average
KE as the particles slow down and run into each
other less.
Page 2:
Page 4:
1. The temperature of a substance is related
to: (c)
1. What will happen to the temperatures in
the chambers if the temperature of the left
one is higher than that of the right one? (d)
2. A substance composed of atoms A and
another composed of atoms B are at the
same temperature, but atom A is ten times
more massive. How does the speed of A
compare to the speed of B, on average?
2. What do you think happens that causes
both chambers to reach the same
temperature in the above simulation?
The speed of atoms A will be slower than the
average speed of atoms B. The more massive
the atoms, the slower they will move when the
temperature is held constant.
The particles are moving randomly and colliding.
As they do, they transfer their KE to each other
including to atoms in the other container. In an
open system, these interactions will continue
until the temperature is the same in both.
3. Which type of atom has the greater mass?
(a)
Page 5:
4. The yellow and pink atoms in the container
are the same temperature. Use what you
know about kinetic energy to explain what
you observe in the model.
1. Write down the temperatures of the large
and small solids after you have hit the "Add
energy" button 10 times. Describe the
relationship between the readings and the
size of the solids.
The total KE is the same for both the pink and
yellow atoms. You can see that the less massive
atoms (the yellow) are moving faster because
they are affected more by the temperature than
the more massive atoms (the pink).
Page 3:
1. What did you observe about the kinetic
energy (KE) of the atoms? (e)
2. If we add another box to the model, the
average kinetic energy of atoms within the
box will: (a, b and e)
3. Describe how changing the number of
atoms in the box (by changing the size)
affects the temperature. (c)
For a large solid, the average temperature was
about 400K after hitting the "Add Energy" button
ten times. For a small solid, the average
temperature was approximately 800K. As the
size of the solid increases, it takes more energy
to increase the temperature of the system. This
is because there are more atoms that need to be
"hit" or impacted by the transfer of energy.
2. How many times do you need to click the
"Add energy" button on the small solid to
reach approximately the same temperature
of the large solid after you hit the "Add
energy" button 10 times?
(b)
Page 6:
1. Which one in the above results in the
fastest heat transfer between the hot and
cold solid?
(b)
2. A radiator heats a house by pumping a hot
liquid through tubes folded as shown in the
image on the left. What do you learn from the
experiment on this page that can explain why
the tube is made in such a shape?
Heat conduction will be most efficient using this
shape. The thin, short tubes that turn many
times offer a lot of surface area for heat
conduction with the colder surrounding air to
take place.
Page 7:
.
1. How is thermal radiation different from
heat conduction in transferring heat? (Check
all that apply.)
(b) (c)
Page 8:
1. Take a snapshot of the model that shows
thermal expansion, and then follow the
instruction below to drag in the snapshot
image.
Sample snapshot: This snapshot of the graph
shows an increase in energy when the solid is
being heated.
Page 9:
1. What is true of the kinetic energy of each
individual atom when a substance has
reached a certain temperature?
(b)
2. Which of the following means of heat
transfer explains why Jane's hand was
burned after she touched the hot pot?
(a)
3. When a hot and cold object are placed in
contact, the hot one loses energy. Does this
violate energy conservation? Why or why
not?
This does not violate the Law of Energy
Conservation of a system. Although the hot
object loses energy, the cooler object will gain
energy. As a system, energy is conserved.
Sample snapshot: Thermal expansion is shown
here because the volume of the heated solid has
increased.
2. Take a snapshot of the graph that shows
the increasing of energy when heated, and
then follow the instruction below to drag in
the snapshot image.
4. When you place a hot cup of tea down,
why does the cup of tea get cooler and the
counter get warmer? Be sure to talk about
kinetic energy and temperature in your
explanation.
Heat is being transferred from the cup of tea (the
object with the higher temperature) to the
countertop (the object with the lower
temperature). The kinetic energy of the atoms in
the cup of tea is being transferred to the atoms
in the countertop. The temperature, therefore,
decreases in the cup and increases in the
countertop.
5. A vacuum flask (sometimes called a
Thermos bottle) is a double-wall container
with a vacuum between the two walls. How
does the flask keep its contents hotter than
the outside air?
A vacuum is an extremely poor conductor of
heat. Placing a vacuum between the two walls
keeps the contents hotter than outside air
because the presence of the vacuum limits the
transfer of heat. Heat will ultimately be
transferred slowly through the cap (for example),
but will keep the substance much hotter than
another type of container.
6. A gas contains equal numbers of atoms of
radon (atomic mass = 222) and helium
(atomic mass = 4). In equilibrium, which kind
of atom is a) going faster, b) has more
average KE, and c) is hotter? Explain your
answers.
a) The helium atoms are moving faster
because they are lighter, according to
2
the equation KE = ½ mv .
b) The average KE is the same for all of
the atoms in the gas because KE is
being transferred from atom to atom as
they collide.
c) The average temperature is the same
for all of the atoms in the gas. If heat is
added to the system, the KE of the
atoms will increase.
SAM HOMEWORK QUESTIONS
Heat and Temperature
Directions: After completing the unit, answer the following questions to review.
1. What is the difference between the terms heat and temperature?
2. How is the movement of air molecules different in the summer than in the winter?
3. Explain the following statement: Temperature in a system is a measurement of the
average kinetic energy of the molecules in that system.
4. What happens to the kinetic energy of molecules in a system as they collide?
5. Explain how the snapshot to the right is an illustration of
thermal expansion.
6. Heat conduction refers to heat flowing from a hot body to a cold body when they come
into contact. Give an example of heat conduction that you have observed in everyday life.
Then explain what is happening at the atomic level. Are all substances equally good at
conducting heat?
7. Career Connection: Find a picture of a computer model that is modeling some form of
heat transfer and give a brief description of the illustration. Examples might be home
design to maximize energy efficiency, or new materials that help move heat away from
electronics like computer chips.
SAM HOMEWORK QUESTIONS
Heat and Temperature – With Suggested Answers for Teachers
Directions: After completing the unit, answer the following questions to review.
1. What is the difference between the terms heat and temperature?
Temperature is a measure of average kinetic energy while heat is the transfer of energy from hot systems to
cold systems.
2. How is the movement of air molecules different in the summer than in the winter?
Air molecules are in greater motion in the summer because the temperature is higher than in winter. Their
increased kinetic energy causes more collisions between molecules.
3. Explain the following statement: Temperature is a measurement of the average kinetic
energy of molecules in an isolated system.
The average kinetic energy is the total kinetic energy divided by the number of atoms. Temperature is a
measure of the kinetic energy of all the atoms in the isolated system.
4. What happens to the kinetic energy of molecules as they collide?
Some atoms have higher kinetic energy and some have lower kinetic energy. When they collide energy from the
atom with the higher kinetic energy is transferred to the molecule with lower kinetic energy.
5. Explain how the snapshot to the right is an illustration of
thermal expansion.
As a substance is heated, 1) the temperature increases and 2) atoms move
apart, thus taking up more space. Thermal expansion, which is an increase
in volume, is shown by the atoms over the original line.
6. Heat conduction refers to heat flowing from a hot body to a cold body when they come
into contact. Give an example of heat conduction that you have observed in everyday life.
Then explain what is happening at the atomic level. Are all substances equally good at
conducting heat?
If you put a hot cup of soup down on the counter, it gets cold over time. The kinetic energy of the atoms in the
cup of soup is being transferred to the atoms in the countertop. No, all substances are not equally good at
conducting heat.
7. Career Connection: Find an image of heat transfer modeling and give a brief
description.
There are many examples of modeling heat flow. One way to find them is to google “modeling heat flow” and
take a look at the images link to show images matching that search phrase.