How Do Geckos Stick? Using Phenomena to Frame Project-Based Science in Chemistry Classes

[ILLUSTRATION OMITTED] Project-based science (PBS) instruction allows teachers to create learning environments that engage students in authentic investigations and, at the same time, develop understanding of key content ideas and scientific practices. The challenge for teachers, however, is to find phenomena that support sustained student engagement. Understanding how geckos--small lizards belonging to the family Gekkonidae--can "defy gravity" and walk across a ceiling provides one such phenomenon. Despite over 100 years of research, scientists are only now beginning to understand how geckos are able to manage this feat (see "Gecko adhesive power," p. 40). In high school chemistry classes, the story of this research offers a fascinating frame through which students can not only learn valuable content about electrostatic forces, but also engage in authentic scientific practice and explore new technologies based on gecko adhesion. In this article, we describe how the curriculum materials we designed explore the gecko's amazing ability through PBS. Features of PBS In designing our curriculum, we used several key factors inherent to PBS instruction (Krajcik and Blumenfeld 2006; Krajcik and Czerniak 2007). Perhaps most importantly, activities should be organized around a driving question, a question that allows us to justify the material students are learning and to develop meaning. In other words, it is important for students to participate in activities they find interesting and relevant to their lives. In addition, students should be involved in inquiry, which includes scientific practices such as * asking questions, * making predictions, * designing and conducting experiments and investigations, * measuring and collecting data, * analyzing and drawing conclusions, * generating evidence-based arguments and explanations, * revising models and generating new questions, and * summarizing and communicating these findings. Students should conduct these practices not in isolation, but in collaboration with fellow students. Finally, students should produce authentic artifacts that allow them to make their learning visible. Driving questions As part of a larger effort to develop instructional materials in the emerging field of nanoscience (Ristvey and Morrow 2007), we created a chemistry PBS unit focused on the driving question "How do geckos stick?" (see "On the web" at the end of this article). The use of a driving question is the hallmark of PBS (Krajcik and Czerniak 2007). This question guides the structure and content of the curriculum. It should be meaningful to students, possess educational worth, contextualize the content covered, and allow for sustained, deep exploration. As a result, driving questions help create an authentic scientific atmosphere in the classroom as students have scientific discussions within smaller groups and between groups. The challenge for teachers and curriculum designers then is to find driving questions that will allow students to learn important science ideas. We have found that our frame of gecko adhesion--"How do geckos stick?"--serves well as a driving question. Students are naturally interested in how geckos are able to accomplish this feat, and the process of understanding this phenomenon necessitates study of vital chemistry content about electrostatic forces (AAAS 1993, Benchmarks 4D and 4G, pp. 80, 96-97). Moreover, the unit inherently contextualizes this content and provides a multiweek exploration of the phenomenon that maintains student attention and interest. The driving question also sets the stage for students to engage in various investigations to find a solution (Krajcik and Czerniak 2007). Once the question is introduced, students experience the phenomenon of seeing a gecko walk on the "ceiling" of its terrarium. …