Abstract
The teaching of stoichiometry in high school presents challenges related to the articulation between chemical concepts, calculations, and the interpretation of problem situations, highlighting the need for didactic strategies that bring the content closer to meaningful contexts for students. Faced with this problem, this work aimed to develop and analyze an investigative didactic proposal, called CSI Forensic Stoichiometry, designed to approach stoichiometric concepts through the resolution of a fictitious criminal investigation case. The proposal was based on the principles of active methodologies, especially Problem-Based Learning (PBL), gamification, investigative experimentation, and the contextualization of forensic chemistry. This is a qualitative experience report, developed at the Federal Institute of Alagoas – Maceió Campus, with a class of 1st-year students of the Integrated Technical Course in Electrotechnics, organized into three investigative teams. The application was structured in four phases, in which students carried out activities involving chemical balancing, identification of acidic or basic character, experimentation with sodium bicarbonate and vinegar, and integrated analysis of the evidence to identify the suspect. During the activity, QR codes, investigative clipboards, suspect cards, physical evidence, and chemical experiments were used as elements to progress the narrative. The observed results indicated active student participation, interaction among team members, mobilization of chemical knowledge, performance of experimental procedures, and use of evidence to construct the final hypothesis. The spontaneous association between the behavior of the sodium bicarbonate and vinegar reaction and the information present in the suspect cards was particularly noteworthy. It is concluded that the proposal showed potential as a didactic resource to contextualize the teaching of stoichiometry and to promote the articulation between chemical knowledge, experimentation, investigation, and decision-making.