Chemistry on Your Hands: Exploring Touch for the Detection of Heat of Dilution and Learning of Analytical Chemistry Concepts

Understanding some theoretical concepts is a challenging task for undergraduate students, and the use of simple experiments outside of chemistry laboratories is a vital tool to improve their learning. In this sense, this work presents an alternative experiment to teach essential concepts in analytical chemistry. The limit of detection (LOD), limit of quantification (LOQ), and sensitivity were related to the heat released from the dilution of ethanol and water. Hydroalcoholic gels containing 0, 20, 50, and 80% (v/v) alcohol were spread on the wet hands of 100 students. The capacity to sense and differentiate the presence of alcohol in formulations by a temperature increase on hands was correlated with sensitivity, LOD, and LOQ concepts. In the present work, students were able to differentiate samples containing 0% ethanol from samples containing other ethanol concentrations at a 95% confidence level. The same was true for a gel with 80% ethanol. However, the difference between 20 and 50% gels was not perceived. Therefore, it was possible to state that the gel with 0% ethanol is below the LOD and the gel with 80% ethanol is above the LOQ, but the gels with 20 and 50% ethanol are in the range between LOD and LOQ. Sensitivity could be related to the capacity of each student to distinguish (or not distinguish) the different ethanol concentrations. In this sense, the proposed experiment allowed the teaching of theoretical concepts for use in classrooms because it is elementary, fast, and explores students’ senses to aid knowledge construction. This approach could be easily reproduced and could be used safely, even in theoretical classes.