Construção e aplicação de um protótipo de reator utilizando plataforma arduino para discutir conceitos relacionados à estequiometria

Abstract

In the process of teaching and learning Chemistry, several difficulties of understanding on the part of students related to the content of stoichiometry are observed, among them, the lack of understanding regarding the representation of the three levels of chemical knowledge as presented by Johnstone in 1982. To express it symbolically the occurrence of a chemical reaction, as well as the proportionality relations between reactants and products, students are required to have a high level of abstraction of the content to understand a reactional system or phenomenon. In effect, to facilitate the observation of phenomena such as, for example, the reactivity of aluminum metal in an acid medium in a closed system, with a view to favoring the understanding of the concepts underlying stoichiometry, a low-cost equipment called a hermetic reactor prototype was developed. with the Arduino platform (PRHA) subdivided into two stages: hardware construction, software and device testing (E1); and application in the classroom (E2), segmented into six moments in five meetings: initial meeting, identification of previous ideas about chemical reactions; second meeting, instructional class and use of ball-stick models based on Dalton's atomic model to work on chemical proportions; third meeting, instructional class and reuse of ball-stick models focusing on limiting and excess reagent concepts; fourth meeting, application of the PRHA and discussion about the concepts of proportion, product, reagent, chemical expression; fifth meeting, second application of the PRHA and discussion of the limiting and excess reagent concepts, chemical expression and chemical reaction, ending with a question about the application of the PRHA and the learning possibilities that the students could develop. The proposal was applied to twenty (20) students of the 2nd year of high school at the Ceará Institute of Education, in the city of Fortaleza-CE. The results of E1 are related to the tests carried out with the PRHA, they are: need to follow the information in the sensor data sheet, decrease in reaction time due to the increase in the contact surface, unstable variation of the gas concentration detected in the PRHA, and possibility of external mass exchange to the system. In the application stage, students had difficulties to conceptualize chemical reaction, use chemical symbology as well as understand the mathematical proportion relationship of the reaction. In general, it was possible to perceive that misconceptions previously described in the literature, such as the idea of active and passive reagent and dissolution process as a synonym for chemical reaction, remain present in the teaching and learning process of this content of the participants of this research. The management and application of the PRHA by the students was configured as an important moment of discussion about the phenomenon under study, but even so, given the short time in which the PRHA was used, the students let the macroscopic level prevail to the detriment of the other levels of representation of the chemical knowledge proposed by Johnstone (1982) even after experiencing the activity with the use of stick-ball models.