A middle school instructional unit for size and scale contextualized in nanotechnology

Size and scale is a “big idea” in nanoscale science and engineering and is poorly understood by secondary students. This paper describes the design process, implementation, and evaluation of a 12-h instructional unit for size and scale, in a summer science camp for middle school students from a low SES public school district. Instructional activities were designed following a construct-centered design approach and included the use of microscopes, custom-made computer simulations, and 2-D and 3-D scale models. The unit followed a project-based instructional approach and was contextualized with the driving question, “How can nanotechnology keep me from getting sick?” Pre- and post-intervention interviews revealed that students significantly increased their qualitative and quantitative knowledge of the size of objects including atom, viruses, and cells, with an effect size of 0.8 for an overall metric. The campers closed the gap with private middle school students and on some measures surpassed high school students from the same district. The principle of “broad spectrum” curriculum and instruction – activities that target specific advanced understandings but simultaneously scaffold or support the learning of more fundamental, prerequisite ideas – was inductively generated from an analysis of the learning activities.