This article presents the results of the study of explanatory models produced by 81 students of first-year of medicine at the Universidad del Norte in Barranquilla-Colombia. The students face a case in the area of chemistry applied to medicine, through a contextualized problem situation (SPC), constructed from a perspective of teaching chemistry in context. The explanatory models generated by the students were analyzed qualitatively at four moments of the implementation of a teaching proposal. The results obtained at the beginning of the implementation of the proposal indicate that the students did not elaborate any type of explanatory model. However, these arised from the teaching proposal that involves the SPC in which the students begin to generate explanatory models supported by chemistry content and categorized mostly in the research as Descriptive and Interpretative, a situation fostered by the theoretical and methodological coherence of the SPC, which was designed from a perspective of teaching in context based on modeling and leveraged by scaffolding.

Assuming the nature of science (NOS) as a set of items of meta-theoretical content with value for science education, we understand that in this area the prioritised models are generated in the philosophy of science, with the aim of helping citizens to generate answers around the issues of what science is, how it changes in time, and how it relates to its social and cultural context. The purpose of this document is to collect and compare some of what we call 'propositions with high theory-ladenness' in relation to the philosophy of science presented in specialised documents that are references for some members of the community of science education working in NOS.

Asumiendo la naturaleza de la ciencia (NOS) como un conjunto de contenidos metateóricos con valor para la educación científica, entendemos que en este campo se priorizan modelos provenientes la epistemología, con el objeto de que la ciudadanía genere respuestas a las cuestiones de qué es la ciencia, cómo se transforma a lo largo del tiempo y cómo se relaciona con su contexto social y cultural. El propósito de este documento es recoger y comparar algunas de las que llamamos "afirmaciones con alta carga teórica" en relación con la epistemología presentadas en documentos especializados que son fuente de consulta para algunos integrantes de la comunidad de didáctica de las ciencias ocupados de la NOS.

The aim of this article is to promote a better understanding about the important role played by both the history and the philosophy of the science on the teaching of the scientific concepts, theories and models, in particular on the teaching of "the valency" concept; and, how is it presented in textbooks. Thus, a historic and epistemological study of this concept was done in order to define the main criteria to analyze different textbooks that are used at both secondary and university levels of the education in the Colombian system.

El objetivo de éste escrito es reconocer la importancia de la historia y la filosofía de los modelos, teorías y conceptos científicos en la enseñanza de las ciencias, en particular en la enseñanza del concepto de valencia, además de la forma como es presentado éste en los libros de texto. El estudio histórico y epistemológico de este concepto fue realizado desde los criterios establecidos por los autores, aplicado a algunos de los libros de texto utilizados en educación básica y media del sistema educativo Colombiano.