How Students Learn Science in the Classroom (2005) / Chapter Skim
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11 Guided Inquiry in the Science Classroom
11 Guided Inquiry in the Science Classroom
Pages 107-146
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From page 107... ...
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 something about gravitational forces, resist ve forces of air resistance and fi icti on, and the idea of force in general.
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From page 108... ...
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.
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From page 109... ...
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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From page 110... ...
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 questions 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 associated 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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From page 111... ...
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 environment—a "best answer" at this time. This question may be more about understanding buoyancy Than understanding gravity.
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From page 112... ...
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 downward 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 substantially) "because There is no air to hold The object up.
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From page 113... ...
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.
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From page 114... ...
" 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: "Conclusions are different from results.
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From page 115... ...
" Widh some additional discussion among The students, and possibly some additional clanf~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 answers 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.
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From page 116... ...
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.
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From page 117... ...
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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From page 118... ...
In what direction would the water in the container push on the droplet? " With some guidance to think about the directions in which air and water push on a tiny droplet right in the opening of one of the holes, the students conclude that the inside water must be pushing outward (sideways)
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From page 119... ...
I now allow students to major in one activity and visit The odhers. They get engaged in These simple, common activities, and challenged, they need time to come up with and test explanatory ideas so I now plan for students to have two class periods in which to complete their major activity, briefly visit each of The o her activities, and prepare to present Their findings to The class.
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From page 120... ...
" Virtually all students suggest the scale reading will be lower than when the ob ect is weighed out of the water They are given an opportunity to test their predictions and are then encouraged to explain the results. Hi hen complex explanations involving severalfactors are need ad Itir their reasoning, students need more time to put the pieces together The scale reading is lower Some students conclude that the water is pushing up by an amount that is the difference between what the object weighed when out of the water and when in the water Note, however, that this is going back to the conclusion that water pushes up, with no mention of any downward push.
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From page 121... ...
"So, what does all of this tell us about The situation of weighing under The bell jar? If we had a really accurate instrument, what do you drink would have happened to the scale reading and why?
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From page 122... ...
iscussion and Summaty of Learning There are expectations for what students should have learned from the curricular activities performed thus far Up to this point, I have been attempting to identify students' understandings about the pushes of the surrounding fluid (water or air)
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From page 123... ...
When students feel they are ready, they are encouraged to work through computer-presented questions and problem appropriate to the unit being studied. Typical questions related to the key ideas of the preceding activities might juxtapose three situations involving weighing a solid object—the solid object in air, in water, and in a vacuum—each object suspended from a string attached to a spring scale.
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From page 124... ...
Students should be able to see science as involving many que.stSons as yet unanswered Aldhough There are still many unanswered questions about gravity, The students do know a great deal about what it does and about The variables on which The strength of The gravity force depends.
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From page 125... ...
Each system should hang fairly still with the meter stick horizontal (though this is sometimes difficult with students moving around the room) Each is arranged to be what is called a "torsion balance" or "torsion bar " The word "torsion" comes from "torque," which means twist so, we are going to see whether these bars can be made to twist by bringing something near the ob ects hanging from the ends without touching the objects (see Figure 11-2)
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From page 126... ...
a sphere on one end of each torsion bar. (Notice that there is a similar situation on the other end of the torsion bar.
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From page 127... ...
I ir mediately show them what happens: the foam cup does not affect any of the objects (unless the spheres themselves happen to have become charged electrically)
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From page 128... ...
Thinking needs to be challenged wbeneverpassive media are used I show a piece of film dhat demonstrates a torsion balance experiment similar to what we have been observing during The first half of The class period. In the film, a meter stick is again used as The torsion bar in this case,
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From page 129... ...
Then The students watch The film as The bar slowly twists such that The bottles get closer to The boxes Because The effect is so unbelievable to students and because an indirect measure of The movement of The bar is used in the film, I talk the students Through The procedure, The results, and the final conclusion: Student 1 Student 2 Teacher Student 3 Student 4 Teacher Student 3 Teacher Do you understand the procedures How is it like the procedure we used for the magnet situation and the electric charge situations There are things hanging from the stick in all Of 'em. The stick could turn if something made it turn, like a magnet or rubbed foam cup.
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From page 130... ...
I tape a small piece of mirror to the middle of the meter stick with the bottles and shine a flashlight on the mirror This is also done in the film. A spot of reflected light hits the wall over my shoulder I One goal of inquiry-based teaching is to get students to be the ones asking the questions and challenging or bringing up apparently conflicting obser~anons.
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From page 131... ...
Although Sir Isaac Newton, in 1687, suggested every object in the universe pulled on every other object in the universe, it really wasn't until about a hundred years later that another scientist named Hen ry Cavendish built a very sensitive torsion balance and was able to see evidence of gravitational attraction happening with ordinary things in a laboratory. Providing some information from tlbe )
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From page 132... ...
away at all circumstances associated with three different forces that can all act at a distance, even across empty space. We conclude that they all three are "actions at a distance," but they act on different materials.
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From page 133... ...
of Gravitational Force Depends The purpose of the next series of lessons is to build a case for students to believe that the magnitude (size) of the gravitational force grows as each of the two interacting masses becomes larger, and that the greater the separation distance between the two masses, the smaller is the gravitational force that each exerts on the other High school physics students and more mathematically capable middle school students may be able to conclude with analogous experiences from magnetism and electrostatics that the dependence on distance of separation is an inverse square law.
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From page 134... ...
. Set up properly, the magnet attracts the paper clips and the string pulls on the spring scale, registering a reading even without the magnet touching the paper clips.
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From page 135... ...
Other students suggest we might need more paper clips to lessen the force. Since no one has mentioned the separation distance, I ask how it might make the scale reading lower I ask the students to answer the question for themselves first without saying their answers out loud, so everyone has a chance to do the thinking.
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From page 136... ...
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.
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From page 137... ...
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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From page 138... ...
OK. Anything else7 See if more paper clips makes the force reading bigger
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From page 139... ...
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.
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From page 140... ...
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.
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From page 141... ...
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.
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From page 142... ...
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 gravitational 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 between them.
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From page 143... ...
More mature students 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.
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From page 144... ...
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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From page 145... ...
Thus, it is accessible to teachers 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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