Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Presentamos los principales resultados de una metasíntesis realizada sobre investigaciones que en los últimos 40 años han reportado resultados relacionados a las dificultades que conlleva el aprendizaje del concepto concentración de disoluciones en niveles medio y superior. Analizamos, de la muestra de artículos, sus enfoques teóricos, métodos y resultados. El principal resultado de este proceso indica una falta de sistematicidad en las investigaciones realizadas que denotan una vacancia de investigaciones sobre el tema.

This article discusses the H-bridge formation amongst functional groups containing different H-bridge acceptors with OH donors. A series of circular grids is introduced as a visual aid for the organization and the comparison of the diversity of H-bridges present in organic molecules, emphasizing in the case where the H-bridge donor is an OH group (primarily alcohols and phenols). The H-bridges are classified as “unlikely”, “less significant” and “significant” based on experimental and/or theoretical evidence, and analyzed in terms of electronic, steric, thermodynamic, substitutional, or situational effects. Using these grids, students can predict and classify the likeliness of an H-bridge interaction between common organic molecules and understand their effects in more complex systems.

En el presente artículo se discuten dos modelos en química que consideramos obsoletos: el modelo de orbitales atómicos híbridos (HAO) y el modelo de repulsión de los pares de electrones de la capa de valencia (VSEPR). Se presenta una discusión exhaustiva, con ejemplos de moléculas hipervalentes y de elementos de grupo principal, de los conflictos conceptuales que surgen a raíz del uso de los HAO en cursos introductorios de química para la explicación de algunos fenómenos, por ejemplo los supuestos pares de electrones. También, VSEPR muestra ser problemático. La relación entre HAO, VSEPR y las estructuras de resonancia manifesta anomalías.

To resolve several problems that arise in the teaching of hybrid atomic orbitals (HAO) and the valence-shell electron-pair repulsion (VSEPR) model, we propose an original way to present molecular structures, beginning with an analysis of the teaching of lone pairs without HAO and VSEPR. Our purpose in eliminating completely the HAO and VSEPR models from introductory and organic chemistry is to avoid erroneous concepts about the distributions of electronic charge within molecules. We provide a general design to teach the basic curriculum of chemistry in the future without HAO and VSEPR. 

La Resonancia Magnética Nuclear (RMN) es una técnica espectroscópica utilizada en diversas áreas de las ciencias químicas, biológicas y de la salud. Es por ello, que la RMN forma parte esencial de la currícula de los programas educativos a nivel licenciatura en carreras afines a estas áreas. De acuerdo con nuestra experiencia docente, el primer abordaje de los estudiantes para aprender RMN se da a través de la lectura de bibliografía que comúnmente se encuentra  en idioma inglés, por lo que hemos detectado dificultades iniciales, ya que además de la problemática asociada al dominio de la lengua extrajera, los estudiantes también tienen que lidiar con el entendimiento de conceptos de química, física cuántica y matemáticas. En este sentido, el objetivo de este artículo de divulgación es proporcionar un material didáctico que facilite a estudiantes y profesores la introducción a  conceptos básicos de la teoría de RMN con ayuda de ejemplos y analogías. Este documento se recomienda como lectura previa a la impartición de la primera clase de fundamentos de RMN en los cursos de química orgánica, química analítica, química instrumental, y espectroscopía, entre otros.

In this paper, we present and discuss the theoretical and methodological guidelines of an experimental experience with practicing science teachers from different educational establishments in Chile, which aimed to identify and characterize the explanations of the dissolution model based on the elaboration of personal narratives. This was done during a teacher professional development course in which reflection on the relevance of language in the interpretation of experimental phenomena was encouraged. The results reveal the coexistence of diverse typologies of scientific explanation at three levels: microscopic, macroscopic, and symbolic, which is expressed in the emergence of four explanatory profiles on the phenomenon of dissolution, which is partly due to the diversity of the teachers who participated in the study, restricted knowledge of the relevance of language for communicating scientific ideas and a strong emphasis on descriptive and microscopic processes about dissolutions.

For students to learn to write according to the typical ways of each discipline, it is necessary to generate classroom proposals that aim at developing a specific literacy in each subject. This would involve disciplinary teachers as mediators to favor the development of complex written practices. In this work, we present a classroom experience, in which the Chemistry teacher in collaboration with an interdisciplinary team, assumes a mediating role in the construction of explanations related to experiments in which various phenomena occur from a chemical reaction. The writing of explanations promoting interactions in the classroom that will facilitate the task was requested. The methodology used consisted of a workshop in which secondary school students from a school in San Juan (Argentina) carried out experiments and produced written explanations. The results show that, initially, they wrote procedural recounts and / or incomplete explanations. Faced with these difficulties, the tools provided during classroom interaction guided them in the collaborative construction of new explanations. The reflection on their written productions allowed them to rethink and rewrite with improvements in relation to the Chemistry content and the structure of the explanations.

El premio Nobel de Química 2021 fue otorgado a Benjamin List y David W. C. MacMillan por el desarrollo de la organocatálisis asimétrica. El propósito de este artículo es explicar de qué se trata esta herramienta sintética, historia previa a la invención de la organocatálisis y los trabajos que iniciaron este campo por la activación vía enamina e iminio descubiertas por los galardonados al Nobel. Adicionalmente, se menciona la catálisis por enlace de hidrógeno y bifuncional. Se ilustra el alcance de la organocatálisis en la síntesis de los antivirales letermovil y oseltamivir y una sugerencia de cómo incluir la organocatálisis en los cursos de licenciatura.

Viscosity is a key property in multiple process engineering tasks that range from the design and selection of process equipment through to the use of viscosity as a quality index. This paper presents flow curves and data treatment methods applicable to viscosity calculations for non-Newtonian liquid materials and empirical rheological models. Fluid foods, materials of complex structure and composition, were analyzed according to their response to shear stress or shear rate. This work summarizes the instrument, device and test conditions used during such analyses, and the calculation method used to derive the flow curve and viscosity for each test. These examples can assist reproducibility trials and data interpretation for tests conducted with rheometers using conventional geometries.

   This paper approaches from a semanticist point of view one of the structuring themes of chemistry: the periodic table. The anchoring to the structuring themes of chemistry through a current approach to the philosophy of science could introduce, in the teaching of chemistry and the training of chemistry teachers, current, renewed and powerful metatheoretical reflections to understand the nature of chemistry (as an activity) and its theories.