Abstract:

In the teaching of chemistry, the contents must be approached from the integration of three levels of representation (macroscopic, microscopic and symbolic) that characterize the discipline. Although the understanding of these three levels depends on how the teacher guides the processes, the differentiation in the types of concepts and the connection between the levels of representation for these concepts is fundamental for the resolution of chemical problems and the understanding of chemical phenomena, among other skills or competencies. In this line, and even when the curriculum and textbooks consider the levels of representation (chemical triplet), the improvement in learning results will depend largely on how and what types of concepts the teacher presents when teaching chemistry.

Within the framework of a FONIDE project (F911415) we set ourselves the objective of analyzing and describing what teachers teach in organic chemistry and what levels of representation they use in their classes. With a mixed approach, we analyzed a set of 82 videos of chemistry teachers' classes that were evaluated between 2011, 2012 and 2013. Once the videos were reviewed and those organic chemistry classes were selected, a subgroup of 22 videos was formed. To collect information that appears in the teachers' practice and that we observe in the class videos, we use various qualitative-descriptive instruments (registration guideline, list of symbols, systematization and coding guideline, and symbol pattern). For information analysis and data generation we use categorical content analysis for general and specific concepts. In particular for the specific category, we use subcategories of: macroscopic, microscopic and symbolic, differentiating qualitative and quantitative concepts for these three subcategories. In addition, we apply quantitative techniques such as classical statistics (variance, mean, deviation) and multivariate (correlations and Student's t).

In general terms, the results indicated that:
a) a low conceptual organization is observed in the different thematic units taught;
b) a majority of the 82 professors deals with specific qualitative concepts at the macroscopic level;
c) in relation to organic chemistry, the thematic units treated by the 22 professors are related to oil; bind organic molecules; hydrocarbons; polymers and plastic materials; hydrocarbon stoichiometry;
d) in the teaching of the different thematic units the relation of the levels is inverted where the most used level is the symbolic, followed by the microscopic and macroscopic;
e) at a symbolic level, the most discussed conceptual contents are hydrocarbon formulas, compound-molecules, aromatic compound formulas and types of chains.

We consider that the exposed results allow us to design and develop strategies to innovate in the initial and continuous teachers training.

Keywords:

Organic chemistry, representation levels, macroscopic, microscopic, symbolic, teachers training.