The responsive teaching and learning presented below occurred prior to the publication of the Next Generation Science Standards (NGSS); however, students were nonetheless engaged in efforts called for by performance expectations. Although the goal of these lessons was not intended to help students develop an understanding of specific core ideas in science, nevertheless, the responsive nature of the classroom activity and the context for their explorations encouraged students to explicitly discuss those core ideas. This example highlights content, crosscutting concepts and practices straddling NGSS clusters via robust discussions among 2nd grade students. Students use ideas that can serve as seeds for full development of the age-appropriate NGSS core ideas involving forces and motion. Another page showcases similar engagement by 3rd grade students.
Click here to see the dimensions showcased below. You might like to print or keep the dimensions open for easy reference as you go through the toy car discussion.
The year after Carolyn taught 3rd grade in a suburban public school, she was assigned a second grade class. She again launched a physical science unit involving the motion of toy cars. In this responsive teaching environment, ideas about force and motion emerged naturally in the students' discourse. She began by asking students to suggest various ways for getting different toy cars to move, e.g., push cars, propeller cars, balloon cars, pullback cars, windup cars and so forth. Below we share a portion of the unit, first when students are trying to explain the motion of a balloon car, and then later when they explore a propeller car.
In the discussion below each video clip, bold gray text refers to connections with the Framework and NGSS dimensions linked above, specifically the PS2.A. core idea, the cause and effect crosscutting concept or the scientific and engineering practices of Constructing Explanations and Designing Solutions, and Communicating Information. Numbers in parentheses (e.g., 56-59) refer to line numbers in the transcript.
You may find it helpful to first look at each video clip, think about how the class actions and discourse could support development of some of the NGSS, and then read the associated commentary.
In the video below, students discuss what makes the balloon car go.
Video 1: Balloon Car discussion.
Examine Video 1. In this clip, several students predict that when Carolyn lets go of the balloon car, it will move forward. They spontaneously use cause and effect reasoning when explaining their prediction. They talk about how the air goes out the back of the balloon and pushes the car, causing it to move forward. Students are engaged in a discussion that supports developing an understanding of the PS2.A. core idea. More specifically, at the beginning of the clip (28-29) Cyaira predicts that when the balloon car is let go, ‘the wheels is (sic) going to move.” Hannah then clarifies Cyaira’s prediction (“I think what Cyaira is trying to say…”) by saying that if you just hold the car, it won’t move, but when you let go, the air will come out: “it’s gonna push back, and then the wheels can move.”
Carolyn responds by asking Hannah to clarify her prediction, and indicate which way the car will move. Hannah and many others, through both gestures and comments, say the car will move forward (43), with the air going one way and the car going the opposite way (47). Levi says (57-58) the air is going to the back and then will push it (push the car forward). His added comment (62-63) that when all the air is out of the balloon, the car will stop, provides additional evidence to support Levi’s thinking of the situation in terms of cause and effect: the air moving out the back of the balloon creates the push that causes the car to move forward; when the air runs out, the car is no longer being pushed, and it will stop.
Ethan says (67-68) that when the air comes out the back, the car will not go up in the air. Carolyn asks why, and Ethan responds (72-73) that the car is much heavier than the air. There are many possible paths that a responsive teacher can pursue. Carolyn did not pursue this interesting line of reasoning proposed by Ethan, stayed with her original intent instead and did the experiment. When released, the balloon car did move along the carpet, confirming what the students had predicted.
Several days later, after students have talked about the balloon car, Carolyn introduces the propeller car.
Video 2: Propeller Car discussion.
Examine Video 2. At beginning of Video 2, Sierra winds the propeller on the rubber band car and puts the car on the carpet. She predicts (93-94) that it would go, but when she releases it, the car hardly moves. Carolyn immediately asks why it didn’t move (100). The observation that the car hardly moves, along with Carolyn’s question, immediately focuses the class on trying to achieve a specific goal, that of getting the car to move further. Within this context, students can begin to make progress in their engagement in the practice of constructing explanations and designing solutions (offering reasons for why the car does or does not go far, and suggesting ways of getting the car to move further). Different members of the class spontaneously offer their ideas. They suggest that the reason the car did not move very far on the carpet was because the carpet is bumpy, focusing on ‘bumpiness’ as the impediment to motion. Some students further suggest that the car would move better on a smooth surface, like cardboard, since, presumably, that would get rid of the bumpiness. In offering these ways of achieving the goal, the students seem to draw on prior experience and intuitive ideas about bumpiness.
Looking at the clip in more detail, Sierra mentions (102-103) that because the car is on the carpet, it won’t move, but outside (presumably on a smoother surface) it would. Jonathan suggests (105) putting a ramp under it. (He seems to be using the term ‘ramp’ to mean a smooth surface, not necessarily a sloped surface.) Brandon suggests (111-112) the car should be placed on a “flat surface that is not bumpy, like the carpet.” Here he identifies ‘bumpiness’ as the reason why the car does not move very much on the carpet. Jonathan suggests (116-117) putting down cardboard because its flatter surface would help the car move (better). Both Brandon and Jonathan are focusing on the conditions of the surface as an important factor in achieving their goal of getting the car to move further.
As Carolyn winds the propeller, Isaiah explains why winding helps the car move. He says (123-129) that as the propeller is turned, it increases the tension in the string (rubber band), and that makes the string ‘struggle’ to let go. Carolyn asks what he means by that, and Isaiah responds (133-135): “So that means the propeller will spin fast and it’s going to struggle more and more, and the tension is going to be tighter and tighter.” Isaiah’s explanation is partly anthropomorphic in the sense that he attributes a human behavior, struggling, to the string (rubber band). Young children often anthropomorphize inanimate objects; however, we didn't see any evidence of this in Carolyn's third grade video. At the end, when Carolyn releases the car, it moves very far along the cardboard and also along part of the carpet, achieving the class’s goal of getting the car to move much further. Throughout the video clip, the students in Carolyn’s class had multiple opportunities to share their ideas with the class, engaging them in the practice of communicating information.
In Video 3, the class returns to the bumpy carpet. The students suggest winding up the propeller more and observing the car's motion. The effect of twisting the propeller leads the class to start talking about pushes on the car.
Video 3: Propeller Car discussion.
Examine Video 3.After observing that the car moves a large distance along the cardboard, the class next considers how to make the car move further along the carpet (since, as shown in the previous video clip, when Sierra let the car go on the carpet, it hardly moved). Mason proposes a solution (152-160): winding it more and more until knots appear in the rubber band. Then, when the car is released, it would move so fast that it would “skip over all the bumps” in the carpet and go (much further). Carolyn tests the suggestion by winding the propeller a lot and then releasing it on the carpet. It does move quite far, validating Mason’s solution (“Oh, Mason was right!”). Carolyn then asks Sierra why her car did not move far on the carpet, which helps move the class towards engagement in the practice of constructing explanations and designing solutions. Sierra answers (177) that she did not wind the propellers enough, seemingly building on Mason’s idea: if the propeller is not wound enough, then it cannot move fast enough to skip over the bumps, so it does not travel far.
Carolyn then chooses to pursue the reason for why winding the propellers more would make the car move further, offering the opportunity for the class to engage in cause and effect reasoning. Jonathan claims (182-184) that winding gives the car ‘power’; the more winding, the more power (to make the car move). Carolyn follows this up by asking the class where the car gets its ‘power’ (implicitly asking what ‘power’ means). The students begin to talk in more recognizable, tangible terms such as pushes. (In responsive teaching, or any good instructional pedagogy, it is important for students to use words they understand, and that everyone in the discussion understands in the same way, including the teacher!) Max says (189-190) it gets its power from the wind, by pushing back the wind. Carolyn seeks clarification by what he meant by ‘wind,’ since she doesn’t see, feel, or hear any wind in the room around her. Brandon clarifies by saying (195-198) there is air in the room, and when the twisted propeller unwinds, it pushes the air backwards, causing the car to move forward. So, he says, when the unwinding propeller pushes the air back, that is how the car gets its power. Five different students participated in the discussion about why the car moved along the carpet, thus engaging in the practice of communicating information.
At the end of the clip, Adacia likens the situation to a rocket, saying there is ‘wind’ in the rocket, and when the rocket pushes it back, it makes the rocket go forward even faster. The reoccurring use of the term ‘push’ when students talk about how the propeller car affects the motion of the air, and how the moving air affects the motion of the car, is supportive of students engaged with (at least part of) core idea PS2.A.
As we said before, in responsive teaching there are many choices available to teachers regarding which thread in a discussion to pursue. What are some seeds of force and motion ideas in Video 3 that could be pursued? It is apparent that students spontaneously connect pushes as causing motion (e.g., lines 211-213), that pushes have a direction (e.g., line 197), and motion has a direction (e.g., line 204). Carolyn could follow or return to any of these seeds to further develop students’ understanding.
The discussion above suggests places in the students' dialog that could easily launch further exploration of core idea PS2.A. The very nature of PS2.A, force causing changes in motion, facilitates reasoning using the crosscutting concept of cause and effect and the scientific practice of constructing explanations. How are students otherwise engaged in the practices of science? In all instances, students are engaged in the very important practice of communicating and clarifying their ideas for Carolyn and their classmates. Also, as the class proposed ways of getting the car to move further, that discussion could have provided an opportunity for students to begin to engage in the practice of 'planning and carrying our investigations.'
For another example of children exploring force and motion in this project, see video from Carolyn's 3rd grade class the previous year.