Ensino e aprendizagem de isomeria óptica com uso de polarímetro alternativo na perspectiva da experimentação investigativa

Abstract

The teaching of optical isomerism presents significant challenges, particularly due to the conceptual complexity of chirality and optical rotation, compounded by the lack of accessible teaching resources that support practical activities. The absence of su ch resources in schools highlights the need for innovative approaches capable of making learning more effective and contextualized. In this context, this study investigated the role of investigative experimentation in teaching optical isomerism in a techni cal Chemistry course, through the construction and implementation of an alternative polarimeter made from low-cost materials. The objectives included evaluating the pedagogical potential of this approach, contextualizing the content through inquirybased learning, developing and applying a didactic sequence, and using the alternative polarimeter as a teaching tool. This applied, exploratory, and investigative research was conducted with 15 students from the second module of a technical Chemistry course at a public school in Ituverava, São Paulo. The methodology involved implementing a didactic sequence composed of theoretical and experimental activities carried out in both classroom and laboratory settings. Data collection and analysis combined qualitative and quantitative methods to assess learning progress. The construction and use of the alternative polarimeter enabled students to observe, in a practical manner, the effects of optical rotation in chiral substances, enhancing their understanding of optical isomerism and polarimetry. The analysis of questionnaires applied throughout the sequence indicated positive learning outcomes. Questionnaire 3 showed an increase in correct responses compared to Questionnaire 2. In identifying the type of isomerism, the accuracy rate rose from 47% to 87%, and in differentiating spatial isomers using the polarimeter, the rate improved from 53% to 87%. Students were able to experimentally interpret the relationship between solution concentration and rotation angle, which followed a linear model with correlation coefficients (R²) ranging from 0.9929 to 0.9945. The average specific rotation obtained was +65 ± 4.3 degrees, with a relative error of -1.5% compared to the theoretical value, confirming the reliability of the data. The graphs constructed by the students reinforced their understanding of the mathematical relationship between experimental variables and fundamental concepts of optical isomerism. Student reports indicated that experimentation with the alternative polarimeter fostered greater engagement between theoretical and practical activities. The interpretation of experimental data, observation of optical rotation, and graph construction were identified as essential elements of the learning process. The results demonstrated that investigative experimentation stimulated scientific reasoning, contributing to more active learning. The adopted strategy proved effective in integrating theory and practice, highlighting the potential of the alternative polarimeter as an accessible and functional didactic resource for teaching optical isomerism in school contexts with limited infrastructure.