Abstract:

In the science teaching and learning processes, especially chemistry, the contents must be approached from the integration of three representation levels (macroscopic, microscopic and symbolic) that characterize the discipline. The macroscopic level corresponds to the characteristics and properties of real and observable chemical phenomena. Then, the microscopic level corresponds to the abstract representations or models that are present in the mind of a chemistry expert. At the symbolic level corresponds the representation of chemical phenomena at the macroscopic and microscopic level through images, chemical symbols, formulas, equations. In this line, the conceptual repertoire (CoRe) used by teachers, that is, what the teacher teaching in their classes acquires great relevance. Our objective is to identify and describe the conceptual repertoire and its levels of representation in different subjects for the teaching of chemistry at the secondary level in teachers with excellent performances.

For the methodology, a sample design with a 5% error and a 95% confidence interval was proposed. The initial sample was 86 videos of chemistry classes by high school teachers evaluated between the periods 2011, 2012 and 2013, which once reviewed and validated were reduced to 82 videos. To collect information that appears in the teachers' practice and that we observe in their classes, we use various qualitative-descriptive instruments (registration guideline, list of symbols, systematization and coding guideline, and symbology guideline). For the analysis of the information and data generation, we used the analysis of categorical content (general / specific; quantitative / qualitative; macroscopic / microscopic / symbolic) and quantitative techniques such as classical statistics (variance, mean, deviation) and multivariate (correlations and t Student). In addition, we use the variables of gender and performance level to establish correlations.

The main results indicated that in the qualitative and quantitative field, teachers use a greater number of concepts of the general level compared to the level referred to theory, law or model. At the specific level, teachers use a greater number of concepts at the macroscopic level, followed by the microscopic level and the symbolic level. It is relevant to consider that the quantitative field presents a considerably lower number of concepts in all the variables analyzed in this research. In the correlations between the variables of the qualitative and quantitative fields, there are differences in their association depending on the field to which they belong. In the qualitative field, teachers who use more macroscopic concepts use fewer concepts from the microscopic and symbolic levels. Then teachers who use more concepts at the microscopic level also use more concepts at the symbolic level. However, when analyzing the quantitative dimension, the teachers who use concepts at the general level the most also use more concepts at the macroscopic and microscopic levels.

Examining in detail the practices for the teaching of chemistry,, constitutes a necessity and a strategic aspect of education, which is related to the possibility of replicating (modeling, transferring and organize conceptual content) practices quality in the classroom, develop pedagogical content knowledge (PCK), professional knowledge for teaching chemistry and improve teacher training processes.

Keywords:

Representation levels, pedagogical content knowledge, chemestry, teacher training, professional devolpment of teacher.