the potential energy

Report
Clicker Questions for NEXUS/Physics
Atomic Interactions
& Chemical Energy
A note on usage:
The clicker slides in this booklet are meant
to be used as stimuli to encourage class discussion.
They are intended for use in a class that attempts
to help students develop a coherent and sophisticated
understanding of scientific thinking.
They are NOT intended as items to test whether
students are “right or wrong” or “know” the correct
answer by one-step recall if enough cues are given.
This has a number of instructional implications
that are reviewed in general on the next four slides.
The individual slides also contain annotations
discussing their intended use.
Usage: 1
• Feedback
One of the most important values of a clickerresponse system is to provide instructors with
some understanding of what students are thinking.
Good clicker questions can be highly revealing
(and surprising). But the critical fact is not that the
students make mistakes but to use those mistakes
to probe their thinking and find out why.
This raises the importance of a rich subsequent
discussion well above “letting the students know
what the right answer is.”
Usage 2:
• Student-student interactions
The critical value for student learning occurs
in what happens after a clicker question has
obtained a mixed response from the students.
The standard next cue is, “Find someone
who disagreed with the answer you chose
and see if you can convince them.”
After a minute or two of discussion, a second click
may show students having moved dramatically
towards the correct answer. A brief call for who
changed their answer and why can lead to a
useful exchange. When they have not moved
significantly, more discussion is called for.
Usage: 3
• Incompletely specified questions
Some items have questions that are simple if idealized
assumptions are made, subtler if they are not. Part of
the discussion of these items are intended to include
issues of modeling, idealizations, and hidden
assumptions.
• Questions where answers are not provided.
In these items, the intent is to have students come up
with potential answers and have the instructor collect
them and write them on the board.
Occasionally, especially at the beginning of a class, it may
take some time before students are willing to contribute
answers. It can help if you have some prepared answers
ready, walk around the class, and put up the answers as if
they came from the students. This can help students get
more comfortable with contributing.
Usage: 4
• Cluster questions
Some questions are meant to be used as part of a
group of questions. In this case, resolving the answers
to individual questions is better left until the entire
group is completed. The value of the questions are
often in the comparison of the different items and in
having students think about what changes lead to what
differences and why.
• Problem solving items
In these items (indicated by a pencil cluster logo), the
intent is to have students work together to solve some
small problem. After a few minutes, ask the groups to
share their answers, vote on the different answers
obtained, and have a discussion.
This potential energy diagram represents the
interaction between two atoms. It is negative
at its lowest point. This means…
A. An atom can never be at this location, since energy
can’t be < 0.
B. When atoms are separated, energy is released.
C. When atoms start far and move closer, energy is released.
D. Energy must be added to get atoms to separate.
E. Energy must be added to get atoms to move closer together.
F. The fact that the potential energy is negative tells us nothing;
this is just a result of choosing an arbitrary zero point.
G. More than one of these
H. None of these
I. There is not enough information
to answer
A. At r0.
B. At r1.
C. At fairly large
values of r.
NEXUS/Physics Clicker Questions
The figure shows the potential energy
of two interacting atoms. The point with the
minimum value is r0 and the point where
the curve crosses 0 is r1. Where is the force
between the two atoms the largest?
A. Between r1 and r0.
B. Between r1 and ∞.
C. Nowhere.
NEXUS/Physics Clicker Questions
The figure shows the potential energy
of two interacting atoms. The point with
the minimum value is r0 and the point where
the curve crosses 0 is r1. Where is the force
between the two atoms repulsive?
A. Between r1 and r0.
B. Between r1 and ∞.
C. Nowhere.
NEXUS/Physics Clicker Questions
The figure shows the potential energy
of two interacting atoms. The point with
the minimum value is r0 and the point where
the curve crosses 0 is r1. Where is the force
between the two atoms attractive?
You know that two atoms that are far apart
are barely interacting. How is this
represented visually in the PE diagram?
A.
B.
C.
D.
E.
F.
G.
The potential energy approaches zero as r gets large.
The PE curve is close to horizontal as r gets large.
The PE curve is close to vertical as r gets small.
The potential energy has a minimum.
More than one of these
The PE diagram doesn’t demonstrate this information
None of these
These two atoms can exist in a stable
bound state. How is this represented
visually in the PE diagram?
A.
B.
C.
D.
E.
F.
G.
The potential energy approaches zero as r gets large.
The PE curve is close to horizontal as r gets large.
The PE curve is close to vertical as r gets small.
The potential energy has a minimum.
More than one of these
The PE diagram doesn’t demonstrate this information
None of these
A. They are in a bound state.
B. The total energy of the
molecule is positive.
C. The total energy of the
molecule is negative.
D. The total energy of the
molecule is zero.
1.
2.
3.
4.
5.
6.
7.
Only A
A and B
A and C
A and D
Only B
Only C
Only D
NEXUS/Physics Clicker Questions
Two atoms interact with a potential energy
between them that varies as a function of
their separation as shown in the graph at
the right. We take the zero of energy to be
when they are very far apart and at rest.
They have a total energy E1 as shown on
the figure. Which of the following
statements are true about them?
If the atoms were in the state labeled E1,
which of the statements below are true?
A. To pull them apart, you would
have to put in an energy E1.
B. To pull them apart, you would
have to put in an energy -E1.
C. By pulling them apart, you
would gain an energy E1
that you could use elsewhere.
D. By pulling them apart, you
would gain an energy -E1
that you could use elsewhere.
While wandering around their environment,
the molecule collides with another (fast moving)
molecule and winds up being shifted to the state
with a total energy E2 as shown on the figure.
Which of the following statements are now true
about these atoms?
A. They are no longer in a bound state.
B. They are more tightly bound
than they were before.
C. There are less tightly bound
than they were before.
D. Their binding energy has not
changed.
E. More than one is true.
F. None are true.
While wandering around their environment, the molecule
collides with another (fast moving) molecule and winds up
being shifted to the state with a total energy E2 as shown
on the figure. After the collision it winds up with a total
energy E2 as shown on the figure. The molecule that
struck them does not change its internal (chemical)
energy in the collision. Which of the following statements
is true about the molecule that struck them?
A. It has less kinetic energy after the
collision than it had before.
B. It has the same kinetic energy
after the collision as it had before.
C. It has more kinetic energy after
the collision than it had before.
D. There is not sufficient information
to decide.
What can you say about the average
separation between the two atoms
when they are in the states shown on
the diagram?
A. When the atoms in the molecule
have an energy E1 the atoms are
on the average closer together than
when they have an energy E2.
B. When the atoms in the molecule have an energy E2
the atoms are on the average closer together than
when they have an energy E1.
C. In both cases, the atoms are, on the average, the
same distance apart.
The figure below shows the interaction
potential between two molecules (along
a particular orientation of the two molecules).
The units are in nm (r) and eV (U).
When the molecules are separated by 7 nm
the force between them is
A.
B.
C.
D.
Attractive
Repulsive
Zero
Cannot be determined from
the figure.
The figure below shows the interaction
potential between two molecules (along
a particular orientation of the two molecules).
The units are in nm (r) and eV (U).
When the molecules are separated by 2 nm
the force between them is
A.
B.
C.
D.
Attractive
Repulsive
Zero
Cannot be determined from
the figure.
The figure below shows the interaction
potential between two molecules (along
a particular orientation of the two molecules).
The units are in nm (r) and eV (U).
When the molecules are separated by 0.5 nm
the force between them is
A.
B.
C.
D.
Attractive
Repulsive
Zero
Cannot be determined from
the figure.
The Gauss gun
1. Sphere 1
(when 2 and 3 are NOT there)
2. Sphere 3
(when 1 and 2 ARE there)
3. They will be the same.
NEXUS/Physics Clicker Questions
Spheres numbered 1, 2, and 3
all “stick” when added
one at a time. Which is
more tightly bound?
The Gauss gun
A. Sphere 0 will stick.
Nothing else will happen.
B. Sphere 3 will be kicked off at the same
speed that sphere 0 hit with and will slow
down to a stop – reversing what 0 did as it
approached.
C. Something else will happen. (What?)
NEXUS/Physics Clicker Questions
When sphere 0 is released it is attracted to
the magnet and begins to speed up. What do
you think will happen when it hits
the magnet?
Which describe(s) the difference between
a strong and a weak chemical bond
between two atoms?
I.
II.
The strong bond stores more
energy than the weak bond.
More energy is needed to
separate strongly bonded
atoms than weakly bonded
atoms.
III. More energy is released to
the environment when two
atoms become strongly
bonded than when two atoms
become weakly bonded.
A.
B.
C.
D.
E.
F.
I only
II only
III only
II and III only
I, II, and III
None

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