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475
11
Guided inquiry in the Science Classroom
James Minstrell and Pamela Kraus
The story of the development of this piece of curriculum and instruction
starts in the classroom of the first author more than 25 years ago. I had
supposedly taught my classes about universal gravitation and the related
inverse square force law. The students had performed reasonably well on
questions of the sort that asked, "What would happen to the force if we
increased the distance from the planet?" They supposedly understood some-
thing about gravitational forces, resist ve forces of air resistance and fi icti on,
and the idea of force in general. Then came a rude awakening.
I don't remember why, but we happened to be talking about a cart
being pulled across a table by a string attached to a weight over a pulley.
The students were becoming confused by the complexity of the situation.
So, in an attempt to simplify the context, I suggested, "Suppose there is no
diction to worry about, no rubbing, and no faction." Still the students were
confused and suggested, "Then there would be so much wind resistance." I
waved that notion away as well: "Suppose there were no fliction at all and
no air resistance in this situation. Suppose there were no air in the room.
Now what would be the forces acting on this cart as it was moving across
the table?"
I was not prepared for what I heard. Several voices around the room
were saying, in effect, "Then things would just drift off the table. The weight
and string and cart would all just float away." I was tempted to say, "No,
don't think like that." I suppressed that urge and instead asked in a
nonevaluative tone, "Okay, so you say things would just float away. How do
you know that" They suggested, "You know, like in space. There is no air,
and things just drift around. They aren't held down, because there is no air
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476 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM
to hold Them down." The students said dhey knew tills because dhey had
heard from The media dhat in space Things are weightless. Indeed, dhey had
seen pictures of astronauts just "floating" around. They had also been told
that There is no air in space, and they put The two (no air and weightless)
together But they had no first-hand experiences to relate to what they knew
Tom these external "authorities."
ffwe realty want to know u *at students are to inking, we need to ask then
and then be quiet and listen respectfully to u *at they say. ffwe are genuinely
interested and do not evaluate, we can learn fron/ our students.
What good is having my students know the quantitative relation or equa-
tion for gravitational force if dhey lack a qualitative understanding of force
and The concepts related to The nature of gravity and its effects? They should
be able to separate The effects of gravity from The effects of The surrounding
air Later, they should be able to explain The phenomena of falling bodies,
which requires dhat dhey separate the effects of gravity from Those of air
While many physical science books focus on The constancy of gravitational
acceleration, most students know dhat all things do not fall widh The same
acceleration. They know that a rock reaches The floor before a flat sheet of
paper, for example. Not addressing The more common situation of objects
falling differently denies The students' common experiences and is part of
The reason "school science" may not seem relevant to Them so, we need to
separate The effects of air from those of gravity.
l earning is an active process. We need to acknowledge students'attempts to
make sense of their experiences and bed them confront inconsistencies in
their sense making.
Even more fundamental, I want my students to understand and be able
to apply the concept of force as an interaction between objects in real-life
situations. They should have first-hand experiences dhat will lead to The
reasonable conclusion dhat force can be exerted by anydhing touching an
Object, and also that forces can exist as "actions at a distance" (i.e., without
touching The object, forces might be exerted Through The mechanisms of
gravity, electrostatic force, and magnetic force).
I also want my students to understand The nature of scientific practice.
They should be able to interpret or explain common phenomena and design
simple experiments to test Their ideas. In short, I want Them to have The skills
necessary to inquire about The world around Them, to ask and answer their
own questions, and to know what questions they need to ask Themselves in
the process of thinking about a problematic situation.
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GU DED INDU BY N THE SC ENCE CEASSFDDM 477
Tetl< hers questions can model the sorts of questions students might ask them
selves when conductSngtersonal inquiry
Research and best practice suggest that, if we are really clever and care-
ful, students will come more naturally to the conceptual ideas and processes
we want them to team. Being clever means incorporating what we have
come to understand about how students learn. This chapter describes a
series of activities from which the experience of teachers and researchers
demonstrates students do learn about the meaning of force and about the
nature and processes of science. It also explains how the specific activities
and teaching strategies delineated here relate to what we know from re-
search on how people learn, as reflected in the three guiding principles set
forth in Chapter 1 with regard to students' prior knowledge, the need to
develop deep understanding, and the development of metacognitive aware-
ness. We attempt to give the reader a sense of what it means to implement
curriculum that supports these principles. It is our hope that researchers will
see that we have built upon their work in designing these activities and
creating the learning environment. We want teachers to get a sense of what
it means to teach in such an environment. We also want readers to get an
idea of what it is like to be a learner
The following unit could come before one on forces to explain motion
(i.e., Newton's Laws). By the end of this unit, students should have arrived at
a qualitative understanding of force as applied in contexts involving buoy-
ancy, gravitation, magnetics, and electrostatics. The activities involved are
designed to motivate and develop a sense of the interrelationships between
ideas and events. The expected outcome includes qualitative understanding
of ideas, not necessarily formulas.
THE UNIT: THE NATURE OF GRAVllY AND
ITS EFFECTS
Part A: What Gravity Is Not
Getting the Unit Started Finding OutAbout Students'lnitial Ideas
Teachers need to u n co ad ition n TV respect students'capacStSesfor learn ing
complex ideas, and students need to learn to respect the teacher as an
instructional leader Teachers wSII need to earn that respect through their
actions as a respectful guide to learning.
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478 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM
For students to understand the following lessons, we need to establish
some prerequisite knowledge and dispositions during earlier lessons stu-
dents will need to understand that measurements of a single quantity may
vary depending on three factors: the object being measured, the instrument
being used, and the person using the instrument. The teacher needs to have
enough experience with the class so that the students are confident that the
class will achieve resolution over time. Thus, this unit comes about a month
or so into the school year Students need to persevere in learning and trust-
ing that the teacher will help guide them to the big ideas. This should prob-
ably not be the students' first experience with guided inquiry. While the set
of experiences in Part A below takes a week or more to resolve, prior initial
experiences with guided inquiry may take a class period or two, depending
on the students' tolerance for ambiguity.
Identif,uing PreconceptionsWhat Would Happen If . . . ?
Tea< hers need to knou students' initial and developing conceptions. Students
need to Kate their initial ideas brought to a conscious le.uel
One way to find out about students' preconceptions for a particular unit
is to ask them to give, in writing, their best answers to one or more ques-
tions related to the unit. At the beginning of this unit on the nature of gravity
and its effects, the teacher poses the following situation and questions asso-
ciated with Figure 11-1,
- Vacuum inside a bell jar
Nature and Effects of Gravity
Diagnostic Question
Scale reading = 10.0 Ibs
<~\~N Glass dome with
~L~ air removed
Scale reading = Ibs
FIGURE 1 1 1 A diognoshc queshon lo use oi he beginning of his unit
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GU DED INDU BY N THE SC ENCE CEASSFDDM 479
Nature and Effects of Gravity, Diagnostic Question 1: Predict The scale
reading under The glass dome with air removed.
In the diagram with question 1, we have a large frame
and a big spring scale, similar to what you might see at the
local market. Suppose we put something on the scale and
the scale reading is 10.0 lb. Now suppose we put a large
glass dome over the scale, frame and all, and seal all the
way around the base of the dome. Then, we take a large
vacuum pump and evacuate all the air out from under the
dome. We allow all the air to escape through the pump, so
there is no air led under the glass dome.
What would happen to the scale reading with no air
under the domes You may not be able to give a really
precise answer, but say what you think would happen to the
scale reading, whether it would increase, decrease, or stay
exactly the same and if you think there will be a change,
about how much 7 And briefly explain how you decid em
I will not grade you on whether your answer is correct. I
just want to know your ideas about this situation at this
time. We are just at the beginning of the unit. What I care
most about is that you give a good honest best attempt to
answer at this point in time. I know that some of you may be
tem pted to say HI don't know, ~ but just give your best
answer at this time. I'm pretty sure most all of you can come
up with an answer and most importantly some rationale to
support that answer. Just give me your best answer and
reasoning at this point in time. We will be working to
investigate this question over the next few days.
When asked, more than half of students cite answers that suggest They
believe air only presses down. Half of Those suggest that The scale reading
would go to zero in the vacuous environment. About a Third of introductory
students believe That The surrounding air has absolutely no effect on The
scale reading regardless of The precision of The scale. Most of The rest believe
that air only pushes up on The object and That it does so with a strong force.
Typically, only about one student in a class will suggest that The air pushes
up and down but widh slightly greater force in the upward direction, The
result being a very slight increase in the scale reading for The vacuous envi-
ronment—a "best answer" at this time.
This question may be more about understanding buoyancy Than under-
standing gravity. However, part of understanding the effects of gravity is
learning what effects are not due to gravity.
.~udenh nerd opporf unit /es f o explore /he relof ionships among /deai
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Gravitational force is an interaction between any two objects that have
mass. In dais case, the gravitational force is an interaction between the ob ect
on the scale and the earth as the o h e- object. Many students believe gravity
is an interaction between the object and the surrounding air Thus, tills has
become a first preconception to address in instruction. If teachers fail to
address dais idea, we know from experience that students will likely not
change Their basic conceptual understanding, and teachers will obtain The
poor results described earlier.
In contrast with The above question, we have seen curricula dhat attempt
to identify students' preconceptions simply by asking students to write down
what They know about X. In our expenence, this question is so generic that
students tend not to pay much attention to it and simply "do The assignment"
by writing anything. Instead, preinstruction questions should be more spe-
cific to a context, but open up The issues of The discipline as related to that
context. These sorts of questions are not easy to create and typically evolve
out of several iterations of teaching a unit and finding out Through discus-
sions what situations elicit the more interesting responses with respect to The
content at hand.
A Benchmark Lesson' TWeighing in a Vacuum
In discussion following The posing of this question, I encourage stu-
dents to share Their answers and rationales. Because I am interested in get-
ting students' thinking out in the open, I ask that odher students not com-
ment or offer counter arguments at This point, but just listen to The speaker's
argument. 1, in turn, listen carefully to The sorts of Thinking exhibited by The
students. I know This will faciliate my helping The class move forward later
Widh encouragement and support on my part, some students volunteer
to share their answers. Some suggest The scale will go to zero "widh no air to
hold The object down." Others suggest, "The scale reading will not go to
zero but will go down some because gravity is still down and The weight of
the air pushes down too, but since air doesn't weigh very much, the down-
ward air won't be down much and The scale reading won't go down much,"
Some students suggest dhat The scale reading will increase (slightly or sub-
stantially) "because There is no air to hold The object up. it's about buoyancy.
The air is like water Water pushes up and so does air. No air, There is no
buoyancy." Still odhers suggest dhat the scale reading should stay the same
"because air doesn't do anything. The weight is by gravity not by air pres-
sure." And odhers agree that the scale reading will not change, "but air is
pushing on the ob ea. It pushes up and down equally on The object, so
There shouldn't be any change." By now several students have usually chimed
in to say dhat one or another of The ideas made sense to Them. The ideas are
now "owned" by several class members, so we can discuss and even cnti-
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GU DED INDU FY N THE SC ENCE CEASSFDDM 481
cize the ideas without criticizing a particular person. It is important to be
supportive of free expression of ideas while at The same time being critical
of ideas.
Students are more hkely to share their thinking in a climate where others
express gen nine interest in what they have to say Waiting u nti/ one student
has completely expressed his or her idea fosters deeper thinking on that
speaker's part. Asking speakers critical questions to clarify what they are
saying orto hey them give more complete answers and explanationsfosters
their own engagement and learning.
Widh most of their initial thinking having been expressed, I encourage
students to share potentially contradictory arguments in light of The candi-
date explanations. Students might suggest, "When They vacuum pack pea-
nuts, They take The air away and the weight doesn't go to zero"; or "The
weight of The column of air above an object pushes down on the ob ect"; or
"Air acts like water and when you lift a rock in water it seems lighter than
lifting it out of water, so air would help hold The object up"; or "But, I read
where being on The bottom of The ocean is like having an elephant standing
on your head, so air must push down if it acts like water"; or "Air is just
around Things. It doesn't push on Things at all, unless There is a wind." Some
students begin to say they are getting more confused, for many of these
observations and arguments sound good and reasonable.
Once arguments pro and con for most of The ideas have been expressed,
it is time to begin resolving issues. Thus far, we have been freely expressing
ideas, but I want students to know That science is not based simply on
opinion. We can achieve some resolution by appealing to nature; indeed,
our inferences should be consistent with our observations of nature. I ask,
"Sounds like a lot of good arguments and experiences suggested here, so
how can we get an answer? Should we just vote on which should be The
right answer and explanation?" Typically, several of the students suggest,
"No, we can try it and see what happens L)o you have one of those vacuum
things? Can we do The experiments"
I just happen to have a bell jar and vacuum pump set up in The back
room. First, I bnedy demonstrate what happens when a slightly indated
balloon (about 2 inches in diameter) is placed under The bell jar and The
pump is turned on: the balloon gets larger I ask The students to explain This
result. The students (high school age at least) usually are able to articulate
that I did not add air to The balloon, but The air outside The balloon (within
The bell jar) was evacuated, so The air in The balloon was freer to expand The
balloon
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Attention is extremely important to learn ing.
We hang a weight on The spring scale, put it under The jar, and seal The
edges, and I ask students to "place their bets." This keeps students moti-
vated and engaged. "How many drink The scale reading will increase?" Hands
go up. "t)ecrease?" Many hands go up. "t)ecrease to zero?" A few hands go
up. "Stay exactly The same?" Several hands go up. I start The pump.
It is important to give students opportunities to apply (without being told, if
possible) ideas learned earlier
The result surprises many students. The scale reading does not appear
to change at all. Some students give a high five I ask, "What can we con-
clude about The effects of air on The scale reading?" Some students suggest,
"Air doesn't do anydhing." Sometimes to get past this response, I need to
prime The discussion of implications of The results by asking, "t)o we know
air has absolutely no effect?" A few students are quick to say, "We don't
know That it has absolutely no effect. We just know it doesn't have enough
effect to make a difference." I ask, "Why do you say That?" They respond,
" Remember about measurements, There is always some plus or minus to it. It
could be a tiny bit more than it was. It could be a tiny bit less, or it might be
exactly The same. We can't tell for sure. Maybe if we had a really, really
accurate scale we could tell."
I also want The students to see that conclusions are different from
results, so I often guide them carefully to discuss each. "First, what were
The actual results of the experiment? What did happen? What did we
observe?" Students agree that There was no observable change in The
scale reading. "Those were the results. We observed no apparent change
in The scale reading."
Students should be provided opportunities to differentiate between summanz-
ing obserr able results a nd the conclusions general iced from those results.
Because I want students to understand The role of experimentation in
science, I press Them for a conclusion: "So, what do we know from This
experiment? t)id we learn anydhing?" Aldhough a few students suggest, "We
didn't learn anything," o he- s are quick to point out, "There can't be any big
changes. We know That The air doesn't have a big effect." At This point, it
appears students have had sufficient experience talking about The ideas, so
I may try to clarify the distinction between results and conclusions: "Conclu-
sions are different from results. Conclusions are about The meaning of The
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results, about making sense of what we observed so, what can we con-
clude? What do These results tell us about The effects of The air?" Widh some
additional discussion among The students, and possibly some additional clan-
f~cation of The difference between results and conclusions, most students are
ready to believe The following summary of their comments: "If The air has
any effect on the scale reading, it is not very large. And appal ently gravity is
not caused by air pressure pressing things down."
Actit try A I
Activity Al is a simple worksheet asking students to review their an-
swers to questions about their initial ideas, o her ideas that have come out in
discussion, and The results and conclusions from the preceding benchmark
lesson. Typically, I hand this summary sheet out as homework and collect it
at the beginning of the next class. By reviewing what students have written,
I can identify related issues that need to be discussed further with certain
students. Alternatively, I may ask students to check and discuss their an-
swers with each o he- in groups and to add a page of corrections to their
own answers before handing in their oliginal responses. One purpose of
this activity is to encourage students to monitor their own learning.
Students need opportunities to learn to monitor their own learning.
Progressing from the preinstruction question through the benchmark
discussion takes about one class penod. In showing That gravity is not caused
by air pressure, we have generated questions about the effects of the sur-
rounding air Students now want to know the answer to the original ques-
tion. I used to end The investigations of the surrounding air at this point and
move on to investigating factors affecting gravity, but I discovered that stu-
dents slipped back to believing that air pressed only down or only up.
Therefore, we redesigned the curriculum activities to include more time for
investigation into The effects of surrounding fluids L)oing so also allows us
to incorporate some critical introductory experiences with qualitative ideas
about forces on objects. This experience helps lay the groundwork for the
later unit on forces, when we will revisit these ideas and expenences. To
deepen students' understanding of The effects of surrounding fluids Then, we
now engage in several elaboration activities wherein students have opportu-
nities to test various hypotheses that came up in the benchmark discussion.
Revisiting ideas in new contexts kelps organize then in a rick conceptual
framework and facilitates application across contexts.
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Opportunitiesfor Students to Suggest and Test Related Hypotheses
In the benchmark lesson, several ideas were raised that need further
testing. Some students suggested air only pushed up, others that air only
pushed down, still others that air pushed equally or did not push at all.
Some suggested that air was like water; others contested that idea Each of
the following activities is intended to give students opportunities to test
these ideas in several contexts, recognizable from their everyday world.
That is, each activity could easily be repeated at home; in fact, some stu-
dents may have already done them. One goal of my class is for students to
leave seeing the world differently. Groups of three or four students each are
assigned to "major" in one of the elaboration activities and then to get around
also to investigating each of the other activities more briefly. In every case,
they are asked to keep the original bell jar experiment in mind: "How does
this activity help us understand the bell jar situation?" With respect to the
activity in which they are majoring, they will also be expected to present
their results and conclusions to the class.
Eilaboratlon Activity A2: The Inverted Glass of Water. This activity was
derived from a trick sometimes done at parties. A glass of water with a
plastic card over the opening is inverted. If this is done carefully, the water
stays in the glass. Students are asked to do the activity and see what they can
learn about the directions in which air and water can push. They are also
given the opportunity to explore the system and see what else they can
learn.
Allowing studentsfreedom to explore maygive teachers opportunities to
learn. Teachers need to allow themselves to learn.
My purpose here is to help students see that air can apparently push
upward (on the card) sufficiently to support the card and the water That is
usually one conclusion reached by some students Early in my use of the
activity, however, I was surprised by a student who emptied the water and
placed the card over the open end of the inverted glass and concluded, "It's
the stickiness of water that holds the card to the glass." For a moment I was
taken aback, but fortunately other students came to my rescue. They said,
"At first we thought it might be because the card just stuck to the wet glass,
but then we loaded the card with pennies to see how many pennies the card
would hold to the empty glass. We found it would only hold about three
pennies before the card would drop off The water we had in the glass
weighs a lot more than three pennies. Stickiness might help, but it is not the
main reason the card stays on. The main reason must be the air below the
card."
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This was such a nice example of suggesting and testing alternative ex-
planations Blat I now bring up The possibility of The stickiness being all that
is needed if This idea does not come up in The group presentation. More
recently, o he- students have tested the stickiness hypodhesis by using a
rigid plastic glass widh a tiny (~1 mm) hole in the bottom. When dhey fill The
glass, put on the card, and invert The glass, dhey put Their finger over The
hole. When dhey move their finger off The hole, The water and card fall. They
conclude dhat The air rushing in the hole pushes down on The water and that
the air pushing from under The card is not providing sufficient support. I
now make sure I have plastic cups available in case I need to "seed" the
discussion,
After making These observations, students are ready to draw The tenta-
tive conclusion that the upward push by the air on The card must be what is
supporting most of the weight of the water on the card. They note the water
must push down on the card, and since The stickiness of the water is not
enough to hold The card, There must be a big push up by the air. This
conclusion is reached more easily by more mature students than by middle-
level students. The latter need help making sense of This argument. Most are
willing to say tentatively dhat it makes sense that the air pushes up and are
more convinced after dhey see The various directions in which air pushes in
the odher activities.
ELaboradon Activity A3: inverted Cylinder in a Cylinder of Water. This
activity was derived from some students describing observations they had
made while hand-washing dishes. They had observed what happened when
an inverted glass was submerged in a dishpan of water. In activity A3, a
narrow cylinder (e.g., 100 ml graduated cylinder) is inverted and floated in a
larger cylinder (e.g., 500 ml graduated cylinder) of water Again, students are
asked to see what they can learn about The directions that air and water can
push,
I want students to see dhat air and water can push up and down, and
that The deeper one goes in a fluid, The greater is The push in any direction.
While doing this activity, students observe that The farther down one pushes
The floating cylinder, The more difficult it is to push. Thus, they conclude Flat
The water is pushing upward on The air in The small cylinder, and The push is
greater the deeper one goes. Typically, some students cite as additional
evidence The observation that The water level in The small cylinder rises
within dhat cylinder The farther down one pushes the small cylinder, thus
compressing The air I commend these students for their careful observation
and suggest dhat odher students observe what happens to The level of The
water in The inner cylinder The more The air is compressed, The harder The
water must be pushing upward on The air to compress it, and The more The
compressed air must be pushing upward on The inside of The small cylinder
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504 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM
Sometimes, there are emergent goals that need to be addressed before
returning to the primary instructional goal For exa mple, teach ing about ti e
content may need to moue to the background of the instruction while
teach ing about the processes of science are brought to tbeforeground, et en
though both are always present
Student 2 See, it's what I thought, less paper clips makes
it stronger
Student 3 No it's what I said. Smaller distance makes it
bigger
Student 4 We got too many things happening.
Student 1 I'm getting lost.
Student 3 it's like we studied before about making fair
tests. This isn't a fairtest.
Student 4 Oh yeah.
Teacher OK. Why not, Chris7 Why isn't it a fair tests
Hang in there Tommy Student 11.1 think we
areabouttoclearthisup. Iwill haveyou
decide when the argument and results of the
experiments make sense to you. The rest of
you need to talk to Tommy to convince him of
what you are saying. Chris, you were saying7
Student 3 You gotta keep things constant. Like change
only one thing and keep otherthings constant.
Student 4 Oh yeah, like we did before, make a fair test.
OK, Tommy7
Student 1 No, I don't remember anything about a fair
test.
Student 4 it's like when we said we have to keep all the
things la few students are saying ~variables~l.
Yeah, we have to keep all the variables the
same except one.
Teacher But, does that help you, Tommy7
Student 1 Not really What's it got to do with this experi-
ment7 That was something we did before
when we were studying other stuff.
Student 3 in this experiment we have to keep the number
of paper clips the same and the strong magnet
the same and change the distance. Only
change the distance, if we want to see whether
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GU DED INDU FY N THE SC ENCE CEASSFDDM 505
the distance changes the scale reading.
Otherwise, if we change other things too, we
will not know whether it is distance or some-
thing else that made it bigger
To become learners, independent of authority, students need opportunities to
make sense of experiences And formulate rational arguments.
Student 1 OK. So, what happened7
Student 3 Well, we didn't keep the otherthings, vari-
ables, the same. So, we need to do that to find
out what happens.
Teacher Good, to find out whether that one variable, for
example the distance, affects how big the
magnetic force is. IAt this point, because the
apparatus is difficult to control, I demonstrate
what does happen when we keep the big
magnet and the number of paper clips the
same and just decrease the distance between
the magnet and paper clips. The scale reading
rises.l Now can we tell if varying the distance
affects the forces
Yeah. It does.
Student 2
Teacher How does distance affect force, Tommy7
Which way does it got The smaller the dis-
tance . . .
Student 1 The smaller the distance, the bigger the force.
Does it get smaller if the distance gets bigger7
Teacher Good question. Let's try it. 11 increase the
distance, and the scale reading is lower I So,
what can we conclude now7
Student 1
The bigger the distance the smaller the scale,
and the smaller the distance, the bigger the
force scale.
Teacher Good. Now, what do we need to do to test
whether the number of paper clips makes a
difference in the force7
Student 1 Would we change the paper clips or keep them
the same7
Student 2 If you want to test the paper clips, you change
the number of paper clips and see if that
changes the force.
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506 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM
Student 1 is that right7 Oh! Oh! I get it. So to see if one
thing affects the other thing, you change the
one thing and see what happens to the other
The teacher's questions to clarify students statements help the students
become clearer about what they know.
Teacher That's sounding like you've got the idea of fair
test orwhat is sometimes called "controlling
variables," but could you say it again and say
what you mean by the word "thing," which
you used several times.
Student 1 OK. To see if paper clips affect the scale, the
force, you change the number of paper clips
and see if the force changes. Right7
Teacher Yes, good. Now suppose you wanted to see if
the strength of the magnet affected the force.
What would you do7
Student 1 Change the magnet and see if the force
changed.
Teacher What would you do about the other variables7
Student 2 I'd keep . . . At this point I interrupt to let
Tommy (Student 1) continue his thinking.
Meanwhile, other students are getting restless,
so l let them go ahead with the apparatus and
see what they can find out, which I charge
them with demonstrating later forthe rest of
us. Meanwhile, I continue with Tommy and
anyone else who admits to needing some help
here.l
411 students can learn, hut some need more assistance than others, and some
need more challenge than others.
Teacher
Student 1
Teacher
Student 1
So, Tommy. What are the factors that we want
to investigate here7
See if bigger magnets have a bigger force.
OK. Anything else7
See if more paper clips makes the force
reading bigger
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Teacher
GU DED INDU FY N THE SC ENCE CEASSFDDM 507
Student 5 And see if distance makes the force bigger or
smaller.
Student 1 We al ready saw that one.
Teacher if we changed the number of paper clips and
we changed the magnet, would we know
whether one of these affected the force7
Student 6 Not if we changed both. If we changed both,
one or both might be changing the force.
Teacher So, what do we need to do, Tommy7
Student 1 Oh, do we need to only change one thing, like
change the strength of magnet we use and
don't change the paper clips7
Student 6 And we'd need to keep the distance the same
too right, else that might be changing the force
toot
Good. So,wethinkthatstrength of magnet,
the number of paper clips, and the distance
might all change the magnetic force. So we
just change one of those variables at a time
and keep the others constant and see if the
force changes and in what direction.
Assuming all the students are familiar u ire tee equipment, sometimes it 15
more important to Rep some studentsfocus on tbe argument agile others
wrestle wits tee details of manipulating tee equipment
In a while, I bring the whole class together I help the students sur ma-
nze the ideas they have developed and how the controlled experiments
helped test those ideas. The group that had the challenge to test factors
demor strates the apparatus and the procedures they used to obtain the
following results:
. The more paper clips, the higher the scale reading (keeping magnet
and distance constant).
· The stronger the magnet, the higher the scale reading (keeping num-
ber of paper clips and distance of separation constant).
· The greater the distance of separation, the lower the scale reading
(keeping number of paper clips and strength of the magnet constanO.
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508 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM
Students need assistance in differentiating between results and conclusions.
Results are specific to the experiment, we ite concl usions general ice across
situations.
From these results we conclude that the magnetic force grows larger with
more magnetic "stuff" (paper clips containing iron), with a stronger magnet,
or with closer distance of separation between the big magnet and the iron
Feces.
Building a Bridgefrom Understanding Magnetic Action at a
Distance to Understanding GravitationalAction at a Distance
Analogies can help bndgefrom the known to the unknown am from the
concrete to the abstract
I now illustrate two situations on the front board. One is something like
the situation we have just investigated, with a large magnet pulling on an
iron object and stretching a spring scale. Since this diagram is a bit different
from the previous one, I ask students to discuss the similarities and differ-
ences. When they appear to see that the situations just seem to be different
representations of the same conclusions we drew, I move on to the second
diagram. It looks like the first, except that a large sphere represents the
earth, and the object is anything that has mass (see Figure 11-6). The spring
scale is the same. I ask students how this situation is similar and different
from the weighing of a fish depicted in Figure 11-4.
Iron ~
/EQrt h
FIGURE 1 1 6 Diagramming an analog be veen magnetism and gravity
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Student 5 Oh, it's like, the earth pulls on the object like
the magnet pulls on the piece of iron.
Student 7 They are both actions at a distance.
Student 4 So what. We already knewthat.
Teacher
Student 8
Student 1
Student 3
Teacher
ISo the students appearto recognize the
analogous situations. Now comes the difficult
part.l
From our previous experiments you know on
what factors the magnetic force depends.
Right7
IThere is a chorus of "yes," but I don't trust it
because we now have a different diagram, and
I want to know if the students are transferring
what they know about the previous situation.
Students recite the list: "how much iron,"
"how big (strong) the magnet is," "how far
apart they are." Now reasonably assured, I
move on.|
Teacher What are some possible factors on which
gravitational force might depend, if it acts
similarly to magnetisms
Student 2 Oh. Maybe it depends on the separation
distances
Maybe on the mass of the thing, 'cuz that
would be like the number of paper clips.
Maybe on the strength of the magnet.
No, there is no magnet in the gravity situation.
OK. Hang on. Tommy IStudent 11. there is no
magnet in this situation Pointing to the
gravitational easel, but what might be similar
to the strength of the magnet7
Student 1 The strength of the earth7
To build deep understanding of ideas, students need opportunities to transfer
tlbe ideas across contexts. Tea< hers need to check on this transfer of knowl-
edge to new situations
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510 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM
Teacher it is kind of like the strength of the earth isn't it.
Just like the magnetic force depends on how
big and strong the magnet is, the gravitational
force might depend on how big, how much
mass there is in the earth. Just like the more
magnet we have, the bigger the force: the
more mass the earth has, the bigger the force.
I cannot easily show you, with experiments, on
what factors the gravity force depends. But by
what is called an "analogy," we can make a
good guess at the factors gravity depends on.
If gravity action at a distance acts like magnetic
action at a distance, it should depend on how
much there is of each of the two objects
interacting and on how big the separation
distance is. By careful experiments with
sensitive apparatus like the Cavendish torsion
balance we saw before, scientists have verified
that the guesses we just made work out in
experiments. That is, the gravity force, evi-
denced by the spring scale reading, would be
smaller if the mass of the earth were smaller, if
the mass of the ball being held near the earth
were of less mass, or if the ball were placed
farther away from the earth.
Parts C and D: What Are the Effects of Gravity?
Explaining Falling Bodies
Part A was about "what gravity is not." That is, the effects of the sur-
rounding fluid are not the cause of weight or gravity. But we ended up
seeing that fluids such as air and water can have an effect on scale readings
when we attempt to weigh objects Part B was about the nature of gravita-
tional force being one of the actions at a distance. And by analogy we
concluded that the magnitude of the gravitational force depends on the
masses of the two interacting objects and on the separation distance be-
tween them. Investigations into the nature of forces could stop here or
could continue and focus on gaining a better understanding of the effects
of gravity.
Subsequent investigations in my classes involve explaining the phenom-
ena of falling bodies Part of a rich understanding of falling bodies is to
understand the effects of air (or fluid) resistance as well those of gravity.
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GU DED INDU FY N THE SC ENCE CEASSFDDM 511
Activities in these subunits are more consistent with what is presently sug-
gested in cunicula, so they are not described here. But students' preconcep-
tions, such as "heavier falls faster," need to be addressed. More mature stu-
dents can also quantify The acceleration of freely falling bodies and arrive at
equations describing The motion in free fall. But younger students can gain a
qualitative understanding of free fall as speeding up uniformly, and They can
gain some understanding of favors affecting air resistance.
Explaining Motion of Projectiles
Next investigations, especially for older students, can involve under-
standing the motion of projectiles Preconceptions, including "horizontal
motion slows the vertical fall," will need to be addressed. Understanding The
independence of horizontal and vertical motions is a learning goal. Again
those activities are not discussed in detail here. Suffice it to say that addi-
tional investigations into The nature and effects of gravity will build a stron-
ger relationship between ideas and increase The likelihood that what is learned
will be understood and remembered.
SUMMARY
In This chapter, we have tried to make real The principles of How People
Learn by writing from our experience and The experience of odher teachers,
researchers, and curriculum developers. The sequence of activities described
is not The only one that could foster learning of The main ideas dhat have
been The focus here. Likewise, The dialogues presented are just examples of
the many conversations dhat might take place. Teaching and learning are
complex activities dhat spawn multiple problems suggesting multiple solu-
tions. What we have discussed here is just one set of solutions to exemplify
one set of generalizations about how students learn.
That having been said, the activities described are ones that real teach-
ers are using. But dlis chapter has not been just about activities dhat teachers
can take away and use next week. Our main purpose is to give teachers and
curriculum developers an idea of what it looks like when assessment, cur-
nculum, and teaching act as a system consistent widh The principles of How
People Learn. We have tried to give the reader The flavor of what it means to
teach in a way dhat is student-centered, knowledge-centered, and assess-
ment-centered. By looking at The teacher's decision making, we have at-
tempted to provide a glimpse of what it is like to be a teacher or a learner in
a learning community that is respectful of members of The community while
at The same time being critical of The ideas They voice. Students are encour-
aged to question each odher by asking, "What do you mean by dhat?" "How
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512 HOW STUDENTS LEARN: SC ENCE N THE C ASSFOOM
do you know?" But they are also guided to listen and allow others in the
community to speak and complete their thoughts.
Students' preconceptions are identified and addressed, and subsequent
learning is monitored. This means assessment is used primarily for fommative
learning purposes, when learning is the purpose of the activities in the
classroom. By listening to their students, teachers can discern the sorts of
experiences that are familiar and helpful in fostering the learning of other
students.
Leaming experiences need to develop from first-hand, concrete expen-
ences to the more distant or abstract. Ideas develop from experiences, and
technical terms develop from the ideas and operations that are rooted in
those expenences. When terms come first, students just tend to memorize so
much technical jargon that it sloughs off in a short while. Students need
opportunities to see where ideas come from, and they need to be held
responsible for knowing and communicating the origins of their knowledge.
The teacher should also allow critical questions to open the Pandora's box
of issues that are critical to the content being taught. The better questions
are those that raise issues about the big ideas important to deep understand-
ing of the discipline. Some of the best questions are those that come from
students as they interact with phenomena.
Students need opportunities to learn to inquire in the discipline. Teach-
ers can model the sorts of questions that the students will later ask them-
selves. Free inquiry is desirable, but sometimes (e.g., when understanding
requires careful attention and logical development) inquiry is best guided,
especially when the teacher is responsible for the learning of 30 or more
students. But the teacher does not need to tell students the answers; doing
so often short-circuits their thinking. Instead, teachers can guide their stu-
dents with questions not just factual questions, such as "What did you
see?", but the more important questions that foster student thinking, such as
those that ask students to provide explanations or make sense of the phe-
nomena observed. By listening respectfully and critically to their students,
teachers can model appropriate actions in a learning community. Through
questions, teachers can assist learners in mOIliTOIillg their own learning,
Finally, teachers also need the freedom to learn in their classrooms—to
learn about both learning and about teaching.
NOTES
I We use the term "benchmark lesson" to mean a memorable lesson that initiates
students' thinking about the key content issues in the next set of activities.
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GU DED INDU FY N THE SC ENCE CEASSFDDM 513
2. The computer-based Dia~,moser assessment system described is available on
the web through www.FACET nnovations.com. Thus, it is accessible to teach-
ers and students anytime from a computer with web access and appropriate
browser The concept and program were developed by the authors, hiinst en
and Kraus, Earl Hunt, and colleagues at the University of Washington, FACET
Immovations, Talana Inc., and surrounding school districts. It inc udes sets of
questions for students, reports for teachers, and suggested lessons to address
problematic facets of thinking.
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Representative terms from entire chapter:
paper clips
