Analysis of a didactic sequence on acid-base balance in the 2nd year of high school

Abstract

This article deals with the creation and analysis of an experimental device for teaching and investigating concepts of acid-base solution balance at the High School Level. The experiment took place in the Chemistry discipline, with 2nd year public students, in the city of Feira de Santana, Bahia. Chemistry degree students conducted the investigation as teachers and researchers. The objective was to analyze how the student interacts with a specific medium that contains an experimental device, as part of a teaching strategy on the topic of acid-base chemical balance. The methodology was based on the elaboration and application of an experiment involving the determination of the 𝑝𝐻 in water solution using a natural indicator. The didactic sequence aimed to teach concepts and notions such as chemical equilibrium, Arrhenius acid model, and buffer system. and the validation of the didactic sequence based on the comparison of previous analyses, a priori analysis, and a posteriori analysis, after experimentation. The theoretical framework came from elements of the first-generation Didactic Engineering methodology, proposed by Michele Artigue (1989) and the Theory of Didactic Situations, proposed by Guy Brousseau (2008). The analysis of experimental data and scientific activity played a fundamental role in this process, towards possible learning. The main outcomes of the research corroborate the expectations during the validation stage, which was verified in the advancement of students' language through conceptual advancement. 60% of verbalism obstacle were overcome, in which the expected answers were given, with experimentation contributing to giving meaning to the concepts. Although substantial obstacles persisted, with only 20% progress, these data revealed that the tested didactic model provided advanced conditions for learning.