Download Overview - RI

SAM Teachers Guide
Atoms and Energy
Overview
Students will explore how the Law of Conservation of Energy (the First Law of
Thermodynamics) applies to atoms. They will also explore the implications of heating
or cooling a system. This activity focuses on potential energy and kinetic energy, as well
as energy conservation. The goal is to apply what is learned to both our human scale
world and the world of atoms and molecules.
Learning Objectives
Students will be able to:
 Differentiate between kinetic and potential energy.
 Explain how kinetic energy can be converted to potential energy and vice versa.
 Analyze energy graphs and the motion of objects in a system to learn about the
Law of Conservation of Energy.
 Apply the first Law of Thermodynamics when heating or cooling a system.
 Differentiate between energy transfer in an open system and energy conversion.
Possible Student Pre/Misconceptions
 Energy is associated only with movement.
 Energy is destroyed in transformations from one type to another.
 Gravitational potential energy is the only type of potential energy.
Models to Highlight and Possible Discussion Questions
After completion of Part 1 of the activity:
Models to Highlight:
 Page 3 – Pendulum Model
o Discuss how kinetic and gravitational potential energy are
converted and vice versa. Point out that gravitational potential
energy is not the only type of potential energy in light of common
student misconceptions.
o Link to other SAM activities: Gravitational potential energy is
compared to electric potential energy in future lessons studying
electric current.
 Page 4 – The Model of the Spring (Elastic PE) and Corresponding Graph
o Discuss the relationship between the position of the spring and the
curves for potential, kinetic, and total energy in the graph. Ask
students to share ideas for the snapshots they chose to illustrate the
point of lowest kinetic energy and energy conservation.
Possible Discussion Questions:
 Have student’s brainstorms examples of objects that have kinetic energy
and the factors that impact kinetic energy (mass and velocity).
 List situations besides the pendulum where students can explain how
potential energy is converted into kinetic energy and vice versa. Try to
encourage students to think of examples in addition to those involving
gravitational potential energy.
 Demonstration/Laboratory Ideas: Use a spring or slinky in class to
illustrate the principles of elastic potential energy and conversion to
kinetic energy.
After completion of Part 2 of the activity:
Models to Highlight:
 Page 5 – Model of Interatomic PE and Corresponding Graph
o Point out the relationship between KE and PE as the atoms move
both toward and away from each other. Differentiate the
importance of atoms being in close proximity to that of the spring
example from Day 1. Discuss how total energy still remains
constant.
o Link to other SAM activities: Connect interatomic potential energy
to future lessons such as Electrostatics (attraction and repulsion
between atoms) and Newton’s Laws at the Atomic Scale (forces
between atoms at work at close enough distances).
 Page 6 – Model of Atomic Motion and Corresponding Graph
o Discuss how the color of the atoms indicates the gain or loss of
kinetic energy in the system. Stress how the First Law of
Thermodynamics can be seen in both the model and the graph.
 Page 8 – Model of Energy Transfer
o Differentiate between energy conversion and energy transfer.
Discuss what happens as the divider is withdrawn and what the
effect is on the temperature of both containers.
 Link to other SAM activities: Models on Pages 6-8 link strongly to the next
activity, Heat and Temperature. Discuss the models to lead into the
upcoming differences between heat and temperature.
Possible Discussion Questions:
 Why is the example of interatomic potential energy both similar to and
different from the spring example? (Discuss how the sum of total energy
is still conserved, but how distance between atoms now plays a role.)


Have students explain their understanding of the First Law of
Thermodynamics and give examples of how it applies with heating and
cooling.
Have students brainstorm/share examples of energy transfer in an open
system. How is this different from a closed system?
Connections to Other SAM Activities
The focus of this activity is for students to understand kinetic energy, the
interconversion of potential and kinetic energy and how energy is conserved according
to the Law of Conservation of Energy. The Atoms and Energy activity is supported by
both Atomic Structure and Newton’s Laws at the Atomic Scale. Atomic Structure sets
up a connection between an atom’s composition and how this plays a role in both
attraction and repulsion. In Newton’s Laws at the Atomic Scale students focus on
force, mass, and acceleration, which connects to the forces at work between atoms.
Atoms and Energy supports Heat and Temperature. Temperature is defined by the
kinetic energy of the substance, where atoms are colliding. Students can recognize that
energy is conserved in atomic collisions. In addition, kinetic energy is converted into an
excited state in Excited States and Photons. Once atoms are excited, energy can be
converted into light (as photons). Phase Change is related to the energy atoms have to
use to overcome forces of attraction. Finally, Atoms and Energy supports Diffusion,
Osmosis, and Active Transport and Cellular Respiration. The connections are more
indirect, but still present when discussing active transport and ATP. Chemical energy is
converted into another form of potential energy, electrostatic potential energy. The
fundamental principles of energy conversion and conservation, as shown in the Atoms
and Energy activity, are highlighted once again.
Activity Answer Guide
Page 1:
Introduction, no questions.
Page 2:
1. The faster the ball on the left moved the
kinetic energy of the ball.... (b)
2. The kinetic energy is related to both an
object's speed and its mass. Predict what
would happen to the kinetic energy if the ball
on the left were twice its current mass but
the speed of the ball remains the same.
Sample snapshot 2. The kinetic energy is lowest
in this snapshot where the spring is fully
compressed.
The kinetic energy of the ball on the left would
double if the mass were twice the current mass.
This is true if the speed of the ball remains
constant.
2. Take a snapshot of the graph and label it
with the annotation tools to explain how we
know that energy is conserved in this spring
system.
Page 3:
1. Where is the pendulum when the kinetic
energy is maximum? (a)
2. What happens to the kinetic and potential
energy as the pendulum swings from its
highest point to its lowest point?
The potential energy decreases and the kinetic
energy increases.
Page 4:
1. Take a snapshot of the model on the left
that shows one of the two possible locations
of the balls on the spring when the kinetic
energy is lowest.
Sample snapshot 1. The kinetic energy is the
lowest in this snapshot because the spring is
fully extended.
Sample snapshot.
The total energy of the spring system remains
constant. The total energy is shown as the
straight black line. The graph shows that when
potential energy is increasing, the kinetic energy
is decreasing and vice versa.
3. Use the “Step back” or “Step forward”
button to describe the change in kinetic
energy as the spring moves from the most
compressed position to the most stretched
position.
At the most compressed position, the kinetic
energy is low. When the spring is released, the
stored potential energy is converted into kinetic
energy to stretch the spring. By the time the
spring is fully extended to its most stretched
position, the kinetic energy is low again as it has
been converted back into potential energy.
Page 5:
Page 8:
1. The total energy is the sum of the potential
and kinetic energy. What happens to it over
time, if you do not adjust the strength of the
interaction? (c)
1. The energy level of the circular area on the
right rose because:
2. Take a snapshot of the graph and annotate
it to show the point where there is no force.
When the separator between the two containers
is withdrawn, heat energy from the container on
the left is transferred to the system on the right
until the temperature of the two circular areas is
almost equal.
2. Give one example of something that
comes close to having the same
characteristics of energy transfer as seen in
the model. Explain your choice.
3. Why does the kinetic energy increase as
the atoms move toward each other?
The attraction between atoms causes the kinetic
energy to increase as they move towards one
another.
Page 6:
1. As long as you leave the atoms alone,
what happens to the total energy of the
atoms over time? (c)
2. When atoms collide with each other, they
exchange energy. How does the model show
this? How does the graph show this?
The model shows the exchange of energy
because the atoms with low energy (the lighter
colors) become darker in color after they collide.
The graph shows that as a system, the kinetic
energy increases and decreases, but the total
energy (black line) stays constant.
Answers will vary.
One example is putting a hot pot on a cool
countertop. The heat from the pot will be
transferred to the countertop. The pot's
temperature will decrease as the countertop's
temperature increases.
Page 9:
1. When two or more atoms collide... (e)
2. Explain what it means to say energy is
conserved when two atoms move toward and
away from each other.
Energy is converted from potential energy to
kinetic and back, but the total energy in the
system of the two atoms is conserved.
3. What happens to an atom's kinetic energy
if it collides with an atom that has even less
kinetic energy?
When two atoms with different amounts of
energy collide, energy will be transferred from
one atom to the other.
4. How can you increase a cup of water's
kinetic energy?
Page 7:
1. Describe how the energy of the system
changes when it is heated or cooled.
When the system is heated, the total energy of
the system increases. When the system is
cooled, the total energy of the system
decreases.
Adding heat energy to a cup of water will
increase its kinetic energy. The addition of heat
to the system will cause the water molecules to
speed up their motion and, therefore, increase
their energy.
SAM HOMEWORK QUESTIONS
Atoms and Energy
Directions: After completing the unit, answer the following questions to review.
1. What does the Law of Conservation of Energy state?
2. The kinetic energy of an object is represented by the equation KE = ½ mv2. This means
that the kinetic energy of an object is proportional to what two factors?
3. Look at the pendulum below. Label where the kinetic energy will be highest and lowest.
Do the same for potential energy.
4. The atoms in the model below are in a closed system. As the atoms move, what happens
to their kinetic energy? What happens to the total energy of the system over time?
5.
How would your answers to the above question differ if heat were added to the system?
SAM HOMEWORK QUESTIONS
Atoms and Energy – With Suggested Answers for Teachers
Directions: After completing the unit, answer the following questions to review.
1. What does the Law of Conservation of Energy state?
Energy can never be created or destroyed, but can be converted from one form to another. For example,
electricity can be converted into chemical energy.
2. The kinetic energy of an object is represented by the equation KE = ½ mv2. This means
that the kinetic energy of an object is proportional to what two factors?
Mass and Volume
3. Look at the pendulum below. Label where the kinetic energy will be highest and lowest.
Do the same for potential energy.
Kinetic energy lowest
Potential energy highest
Kinetic energy highest
Potential energy lowest
4. The atoms in the model below are in a closed system. As the atoms move, what happens
to their kinetic energy? What happens to the total energy of the system over time?
The kinetic and potential energy of each individual atom will fluctuate, but the total
energy of the system stays the same.
5. How would your answers to the above question differ if heat
were added to the system?
If the system were heated, the total energy of the system would increase. The total energy is no longer a
constant if outside forces change the conditions of the system.