Investigação do potencial de um indicador natural como proposta para o ensino de ácidos e bases

Abstract

Labeled as complex and difficult to learn science, chemistry, in the wrong way, carries with it this label of being something inaccessible to most students. Due to several negative aspects in the teaching-learning process of basic education, and based on several studies found in the literature, outdated strategies and lack of use of didactic resources collaborate in demotivation in the learning of the discipline. We can also perceive that the constant need for experimental activities is very common in elementary schools; however, such activities can not fill the learning gap because they are used in a demonstrative and meaningless perspective for the learner. The aim of this study was to investigate the efficacy of using a natural acid-base indicator obtained from the alcoholic extract of Centrosema brasilianum as a proposal for an easily obtainable resource in place of commercially sold indicators. From the petals, by maceration, the ethanolic extract was obtained, being it added to solutions of secondary standard of different pH and later added to daily solutions for comparison. Stability tests and their use as a natural acid-base indicator on the titration of neutralization were performed with the extract. The results obtained were promising since the extract showed three changes of coloration as a function of the pH of the medium, as well as good stability when stored at different temperatures and being also easy to produce, it presents viability in the schools and can be a substitute for the indicators which have only two color changes depending on the pH of the medium.