Academic journal article Science Educator

Filling in the Gaps: An Explicit Protocol for Scaffolding Inquiry Lessons

Academic journal article Science Educator

Filling in the Gaps: An Explicit Protocol for Scaffolding Inquiry Lessons

Article excerpt

Introduction

The critical nature of scaffolding for inquiry can be illustrated through a minicase study involving a secondary preservice teacher, identified as Rachel. Rachel was teaching a lesson on synthesis and single displacement reactions to high school chemistry students. It is the authors' experience that preservice teachers, like Rachel, often teach these concepts using a lecture/slide presentation. First they introduce the generic formula for synthesis and single displacement reactions (A + B^C and AB + C ^ AC + B). Next, they present the formulas for the actual chemical reactions, 2Fe (s) + 3O2 (g) ^ Fe2O3 (s) and Zn (s) + 2HCl (l) ^ ZnCl2 (aq) + H2 (g). Finally, the preservice teacher provides the students with reaction problems that involve the students writing a complete and balanced reaction and then identifying the type of chemical reaction.

Rachel did not want to use such a rote procedure. Instead, she wanted her students to experience and think deeply about synthesis and single displacement reactions. She framed her lesson using the Predict, Observe, Explain (POE) instructional model (Gunstone & Mitchell, 1998; Haysom & Bowen, 2010). The POE instructional model directs students to predict what will happen during a hands-on activity or demonstration, complete the activity and/or make observations, record and analyze the relevant data, and devise a scientific explanation for the results.

Rachel divided her students into groups of three to four. After completing a reaction at one lab station, the students moved to a new lab station with a different set of reactants. The lesson appeared to have all of the components of an effective inquiry experience. The students were presented with a problem (What type of reaction is taking place?). They worked in collaborative groups to complete the activity and discuss the results, and they derived their own explanations for what occurred. However, the students failed to learn the targeted science concepts of synthesis and single displacement reactions.

For example, at lab station #4 the students were directed to take a piece of steel wool (iron, Fe) and ignite it (adding oxygen, O2). First, they placed an evaporating dish on a triple beam balance and then zeroed out the dish. Next, they placed a piece of steel wool in the evaporating dish and determined its mass. Finally, they ignited the steel wool using a Bunsen burner and reweighed it.

After observing the reaction, Rachel anticipated the students would "see" the mass of the steel wool increased and conclude that oxygen molecules in the air covalently bonded with the iron atoms in the steel wool. However, the students did not attribute the increase in the mass to oxygen or identify the reaction as a synthesis reaction. Instead, their explanations focused on macroscopic phenomena such as the steel wool was "on fire," and "became heavier." They offered no explanations for the increase in mass of the steel wool other than some type of "experimental error." A few of the students correctly identified the reaction as a synthesis reaction, but they could not offer a reason for their answer. After the lesson, Rachel met with the university supervisor and commented she was surprised the students did not "get it." It was readily apparent to the supervisor why the students did not explain the concept appropriately-insufficient scaffolding.

Students, experience, observe, and explain the physical world at the macroscopic level. Their practical, macroscopic experience with fire is that when objects burn they fall apart and decrease in mass. For example, when a log is placed on a fire the final product, wood ash, appears and feels less dense than the original log. Subsequently, when Rachel's students were asked to describe what happened during the chemical reaction, they focused on the macroscopic attributes such as the formation of a flame and increased heat. In the context of their macroscopic perspectives, the measured increase in the mass of the steel wool was nonsensical and could only logically be explained as some type of error. …

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