There has been much interest in magnetite (Fe[subscript 3]O[subscript 4]) due to its utility in adsorbing high concentrations of arsenic in contaminated water. The magnetic properties of the material allow for simple dispersion and removal from an aqueous system. An inquiry-based laboratory has been developed that illustrates these unique properties of magnetite nanoparticles while developing cross-disciplinary and critical-thinking skills. The versatility of the pedagogic approach makes it suitable for both high school (grades 11 and 12) and college-level STEM (science, technology, engineering, and math) courses. The lab experience exposes students to experimental design, environmental remediation, adsorption, and the surface area-to-volume ratio concept of nanotechnology. (Contains 1 table and 5 figures.)