Smartphones, coupled with small mobile sensors, make it possible to work with near-infrared (NIR) spectroscopy in science classrooms. NIR spectroscopy has become a standard analytical technology in various industries. These new devices enable students to create their own data in real time. This article presents an inquiry-based teaching unit, in which students analyse seemingly identical white crystals in order to find a hazardous chemical substance in the school lab. Using student safety sheets, they develop a risk assessment for themselves and the teacher.