Student Preconceptions
Describe tools used to determine student preconceptions:
Lesson One: Circuit of Inquiries 1.1-1.8:
The circuit of inquires in Lesson One are all designed to bring out students
initial ideas of force, energy, simple machines and motion. During the lessons
in Energy, Machines and Motion students will have the opportunity to address
those early conceptions and address how their thinking as changed.
Lesson 2: KWL Chart:
This tool is designed to draw out ideas about what is a battery, a stored energy
source. Students will write about what they know and what they want to learn. In
Lesson 4 students will enter what they have learned about batteries after they
have experience three lessons and several readings.
Lesson 5: Getting Started
Students are asked to write about what they know or think they know about
forces. Students are asked to list forces that they are familiar with. At the
end of Lesson 5 after experiencing elastic and gravitational forces, students
are asked to define a force as a push or a pull.
Lesson 5: Assessment Probe: Talking About Gravity
Lesson 6: Getting Started
Students are asked to discuss what they know friction with their partners and
with the entire class. Students are then asked to identify a situation where
friction works for you and where friction works against you. Students are then
asked to think about what would happen if there were no friction at all.
Lesson 8: Getting Started
Students are asked to list several example of work being done. Students then
read the “scientific” meaning of work, work=force x distance. Students then
review their initial list for items that would fit the scientific view of work.
Lesson 11: Getting Started
This is the first of three lessons to go over how simple machines can make the
work seem easier by increasing the effort distance and reducing the effort
force. At the beginning of Lesson 11 students are asked if they have ever used a
ramp to help them do something, what the slope of the ramp, was is gentle, or
was it steep. Finally students are asked to think about why people would use a
ramp. At the end of this lesson students are asked if an inclined plane is a
machine.
Lesson 12: Getting Started
Students are asked after looking at several pictures what is a pulley. Students
then answer how pulleys help lift loads and what determines how heavy a load a
pulley can lift. Students then use pulleys to investigate and then answer what
the definition of a machine is in their science notebooks.
Lesson 13: Getting Started
Students are asked to make two drawings to show their initial thinking. First
students are asked to draw something that balances. These are then shared with
partners and the class. Secondly, students are asked how they would use a lever
to lift a rock out of the ground. These activities prepare students to
investigate why levers are simple machines.
Lesson 14/15: Getting Started
Students are asked to think about which is the best machine: an inclined plane,
a pulley or a lever? Students explain what they think would be the best machine.
This leads students into calculating both mechanical advantage and efficiency of
two of the three simple machines.
Lesson 3: Researchable Batteries:
Naïve conception, misconception, incomplete conception~
Students may incorrectly think that electricity is stored in a battery.
Students may incorrectly think that current is put into a battery when the
battery is charged. Students may also think that there is no energy in the
battery until the charging process is complete.
Correct conception by the end of the unit:
The battery actually stores
chemical energy-potential energy that is later transformed to electric potential
energy. Currents flow through the battery and if the battery is being charged
energy flows into the battery as long as it is connected to the battery
charger—energy in the battery increases as the battery charges.
Lesson 4: Storing and Using Energy in a Battery:
Naïve conception, misconception, incomplete conception~
Students may believe that energy used is energy lost forever, that it is gone
or used up.
Correct conception by the end of the unit:
It is true that a battery’s energy may be used up, but it is not gone. The
energy has been converted to other forms (heat, light). All of the energy in a
system can be accounted for, mo matter how many energy transformations take
place.
Lesson 5 Forces (Gravity):
Naïve conception, misconception, incomplete conception~
According to Making Sense of Secondary Science, students may incorrectly
believe that gravity is pushing, pulling or holding. Holding appeared to be the
most common perception of gravity is connected with the air pushing down and the
atmosphere shield prevents things from floating away.
Correct conception by the end of the unit:
Gravity is a force of attractions between all matter. Because of gravity, the
earth attracts other objects and pulls them toward its center. In addition
students will learn that weight is a force of gravity on an object.
Lesson 8:
Naïve conception, misconception, incomplete conception~
Students may incorrectly believe that work is done whenever a force is
applied to an object. Students may incorrectly believe that work is something
physical.
Correct conception by the end of the unit:
A person standing still and holding a bag of groceries does no work on the
groceries until he or she moves them. Because the distance moved is zero, the
product of force and distance moved is zero; therefore the work done on the
groceries is zero.
The scientific sense, work is an abstraction a mathematical quantity used to analyze motion and forces.
Lesson 11: The Inclined Plane
Naïve conception, misconception,
incomplete conception~
Students may incorrectly believe that the inclined plane reduces the
amount of work need to accomplish a task.
Correct conception by the end of the unit:
The work done along the inclined
plane is the same as the amount of work needed to lift the object straight up.
The inclined plane requires a smaller effort force exerted over a greater effort
distance, the same amount of work.
Naïve conception, misconception, incomplete conception~
Students may
incorrectly believe that for the cart to move, the effort force must be a little
larger than the opposing forces are.
Correct conception by the end of the unit:
If the effort forces were larger
than the opposing forces, the cart would accelerate; it would not move at a
constant speed.
Lesson 15: The Efficiency of Machines
Naïve conception,
misconception, incomplete conception~
Students may incorrectly believe that inefficiency means
energy is lost in a system.
Correct conception by the end of the unit:
Energy is not lost in a closed
system; the issue is what forms the energy takes. Frictional forces in a system
turn energy into heat, which in many cases is not a useful form. Generated heat
is often thought of as lost energy, and it is lost in the sense that it is not
in usable form. When heat is included in the energy analysis, however, energy is
shown to be conserved in the system.
Naïve conception,
misconception, incomplete conception~
Students may incorrectly believe that efficiency is
similar to power, that is, a powerful machine is more efficient than a less
powerful machine.
Correct conception by the end of the unit:
A machine may do its work quickly,
put a large amount of input energy may have gone into the machine for a
relatively small output in a very short time.
Lesson 18: The Motion of a Fan Car
Naïve conception, misconception,
incomplete conception~
Students may incorrectly believe that the care keeps
moving because the force of the hand continues to act on the care after it is
released.
Correct conception by the end of the unit:
The hand only exerts a force on
the car only while is it in contact with the car. Forces are pushes or pulls.
The hand cannot exert a push or a pull if it is not touching the care.
Naïve conception, misconception,
incomplete conception~
Students may incorrectly think that acceleration is only
when objects speed up.
Correct conception by the end of the unit:
Acceleration is a change in speed.
If an object speeds up, slows down or changes direction there is acceleration.
Students will use “deceleration” to describe an object slowing down, it is
simply negative acceleration.
Naïve conception, misconception,
incomplete conception~
Students may incorrectly believe that constant force is
required to maintain constant motion or speed.
Correct conception by the end of the unit:
In Lesson 18 the force of the fan is greater than frictional forces, resulting
in a net force that accelerates the fan car. If the fan’s force were equal to
the frictional forces, the car would move at a constant speed.
Lesson 19: The Motion of a Mousetrap Car
Naïve conception,
misconception, incomplete conception~
Students may incorrectly believe that if the pushing
force stops there is ‘force’ but it will run out and the car will stop.
Correct conception by the end of the unit:
After the mousetrap car is released and the force propels the car forward,
the forces on the car are not balanced and the car will slow down and eventually
stop because of friction.