Ensino interdisciplinar de pH

Abstract

The concept of pH is extremely relevant not only for chemistry, but for life. With that in mind, experimental protocols and low-cost materials were developed enabling their teaching in a contextualized way, associating mainly with environmental and health issues. Generally, equipment that performs pH measures has a high cost, being difficult its acquisition by Brazilian public schools, not to mention the lack of a laboratory to carry out practical classes. Based on this, we built a low cost pH meter that has an electronic interface that makes use of an operational amplifier to match the impedance of the digital multimeter with the glass electrode. Pilot experiments, induced as pH variation of a medium, effect of the growth of gram-positive and gram-negative bacteria of the species Staphylococcus aureus and Escherichia coli, respectively. From these studies, the idea arose to develop a low-cost experiment, which uses acid and alkaline products found in commerce and homemade culture media. In public schools with different profiles, we introduce students to pH in a contextualized way, the dynamics consisted of the presentation of a short a lecture on pH for students in the classroom, a demonstrative experimental activity and the application of questionnaires before and after class to assess whether the teaching was meaningfulfor the student. All devices and materials developed showed similar results when compared to their commercial equivalents. The analysis of the questionnaires showed a significant improvement, about 500%, in the understanding of the concept of pH in relation to the students' previous knowledge on the subject. This proposal allows the insertion of demonstrative experimental classes in underfunded basic schools.