Projeto, construção e avaliação de um termômetro eletrônico com aquisição automática de dados e aplicações no ensino de físico-química experimental

Abstract

This study falls within the scope of undergraduate chemistry teaching through inquirybased laboratory using open projects of automatic data acquisition systems. This work studied a thermistor-based temperature-measuring instrument with automatic data acquisition and applications in investigative experimental activities in physical chemistry. The study aimed to the design, development and evaluation of an electronic thermometer with thermistor for automatic acquisition of temperature data in real time and its use in experimental practice activities. The project of the electronic thermometer includes a thermistor type temperature transducer, a signal conditioning circuit, an Arduino platform and an Excel spreadsheet for real-time data representation of temperature versus time data. The results indicate that the thermometer built has a measurement uncertainty of 0,07 °C in the range of -10 °C to 100 °C. This instrument was used as a resource to facilitate the planning and implementation of investigative experimental practices of experimental physical chemistry. The activities involved the determination of enthalpy of decomposition of hydrogen peroxide and the cooling curve of stearic acid (thermometry activity). The organization of thermometry experimental activity followed the pattern of Lawson's argumentation, and was developed in three phases: prediction, experimentation and verification. The experimentation phase followed the open laboratory model. The learning objectives of the activities were organized in cognition levels in accordance with the Revised Bloom's Taxonomy of Educational Objectives. The implementation took place with a group of Experimental Physical Chemistry I students in the first semester of 2015, in March and April, at a public university in the state of Rio Grande do Sul. The data collection instruments were the guides for experimental practical activities used by the participants during the implementation of activities, a multiplechoice test of knowledge and a test for motivation to learn, applied before and after implementation, and the observations of teacher researcher. The knowledge test was analyzed evaluating their reliability and levels of difficulty and discrimination of each item. Non-parametric Wilcoxon signed-rank tests indicate an improvement in the performance of participants for knowledge test (p-value=0,009) and motivation to learn (pvalue = 0,006). The analyses of participants’ responses to activity guides were carried out categorizing items of the guides in cognitive levels proposed by Zoller. Items with cognitive development LOCS level was reached by most of the participants, while the HOCS level, related to the development of hypotheses, was not reached by any participant. The prototype of the electronic thermometer with data acquisition and the experimental activities of thermometry and calorimetry are educational products resulting from this study, and may be used and/or modified to meet the needs of the didactic planning of the chemistry teacher.