The present paper deals with the chemistry that is taught in schools from an epistemological and cognitive approach. We wonder about the meaning that can have the discipline for those who learn without identifying with the academic purposes because they are elementary school students working in a specific context (the school). From this reflection, we propose a chemistry course for initial training of elementary school teachers with a modeler orientation. From an epistemological point of view we are working with the notion of 'theoretical model', which is derived from current cognitive philosophy of science's perspective, which proposes a semantic concept of a scientific theory facilitating the approximation of the phenomena and the theory that explains them. The cognitive dimension leads us to identify the consistency between the experimental interventions of students, their abstract representations and the language they use to explain what they do, what happens and why happens when they intervene in chemical phenomena. We identify the modelling process with a progressive fit between the three dimensions of human cognition to acquire the Chemical Change Model that guides and gives coherence to the lessons. Narratives were used that kept the interest of students and they refined their explanations during the modelling process. Discourse analysis of students during the learning process enabled us to identify the relations students established between their representations and their experimental interventions and the language they used. All this brought a new perspective to assess means for students to progress and to establish comparisons between them.

Este artículo tiene que ver con la química que se enseña en las escuelas desde un enfoque epistemológico y cognitivo. Nos preguntamos el significado que puede tener la disciplina para quienes aprenden sin haber identificado el propósito académico, ya que son estudiantes de primaria que trabajan en un contexto específico (la escuela). Con este propósito planteamos un curso de química para el entrenamiento inicial de profesores con una orientación modelizadora.

In this article is presented a brief systematization about the evolution of the concept of blood circulation that considers the historical period between the conceptions of the Egyptians until century XVII, when Harvey consolidates a ''scientific model of Sanguineous Circulation'' in the human organism. Next, we applied the model of Toulmin to analyze blood flow, valves and cardiac frequency evolution concepts from pragmatic to a realistic perspective. Finally we raised some ideas that could serve as a guide for the education of this concept considering the historical aspects that we had analyzed.

En este artículo, se presenta una breve sistematización acerca de la evolución del concepto de sangre que considera el período histórico que transcurre entre las concepciones de los egipcios hasta el siglo XVII, cuando Harvey consolida un ''modelo científico'' de Circulación Sanguínea en el organismo humano. A continuación, aplicamos el modelo de Toulmin para analizar la evolución de los conceptos de movilidad sanguínea, septum y frecuencia cardiaca desde una perspectiva realista pragmática. Finalmente planteamos algunas ideas orientadoras que podrían servir de guía para la enseñanza de este concepto considerando los aspectos históricos que analizamos a través del consolidado de las ideas expuestas.

Abstract: The principal mission of schools is to educate; i.e., to provide the necessary resources for living as happily and humanly as possible. Science education should contribute to attaining this objective. But people are complicated and sometimes complicate the most obvious issues. In this article, I propose reflecting on the contributions of science education to the future of our students, in a school aimed at educating to live with human values.

Resumen La principal misión de la escuela es educar, es decir, proporcionar los recursos necesarios para vivir de la manera más feliz y humana posible. La enseñanza de las ciencias debería contribuir a alcanzar este objetivo. Pero las personas somos complicadas y complicamos a veces las cuestiones más obvias. En este artículo propongo una reflexión sobre las aportaciones de la enseñanza de las ciencias al futuro de nuestros alumnos, en una escuela cuya finalidad sea enseñar a vivir con valores humanos.