results, about making sense of what we observed. So, what can we conclude? What do these results tell us about the effects of the air?” With some additional discussion among the students, and possibly some additional clarification 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 apparently gravity is not caused by air pressure pressing things down.”

Activity A1

Activity A1 is a simple worksheet asking students to review their answers to questions about their initial ideas, other 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 answers with each other in groups and to add a page of corrections to their own answers before handing in their original 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 period. In showing that gravity is not caused by air pressure, we have generated questions about the effects of the surrounding air. Students now want to know the answer to the original question. 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 students 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. Doing 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 experiences. To deepen students’ understanding of the effects of surrounding fluids then, we now engage in several elaboration activities wherein students have opportunities to test various hypotheses that came up in the benchmark discussion.

Revisiting ideas in new contexts helps organize them in a rich conceptual framework and facilitates application across contexts.

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