Recent articles:
Algunas consideraciones clave, pero generalmente olvidadas, para lograr la comprensión del concepto de cantidad de sustancia
Por Daniel Gil Pérez, Amparo Vilches
La comprensión y el uso correcto de la magnitud ‘Cantidad de sustancia’ y su unidad, el mol, presenta serias dificultades, no sólo para los estudiantes sino también para los profesores. Investigación abundante ha mostrado la alta frecuencia de concepciones erróneas de los profesores y los libros de texto, los cuales interpretan ‘Cantidad de sustancia’ ya sea como un número de partículas o más frecuentemente como una masa, o inclusive ignoran la magnitud, y usan el mol como “la masa atómica o molecular, dada en gramos”.
Nuestro objetivo en este artículo es confrontar las dificultades de los profesores, discutiendo un conjunto de razones para justificar la necesidad de introducir ‘cantidad de sustancia’.
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Daniel Berthelot. Part II. Contribution to electrolytic solutions
Por
Jaime Wisniak
Daniel Berthelot (1865-1927) used the electrical conductivity method to carry on fundamental research on the chemical equilibrium present in highly diluted electrolyte solutions, using the electrical conductivity method. In this way he was able to follow the kinetic details, particularly of the processes taking place in normal or pathological fluids of a living organism. He developed the so-called neutralization curve method, which allowed by simple inspection to judge the march of the reaction. The Académie des Sciences of France awarded him the Jecker Prize for his achievements on the subject.
Keywords: electrical conductivity, neutralization curve method, salts, pathological fluids
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Inquiry: Abilities to develop it and promote learning. Part II. The questionnaire and its application
Por
Kira Padilla, Juana Silvia Espinosa-Bueno, Diana Verónica Labastida-Piña, Andoni Garritz Ruiz
Teachers’ Pedagogical Inquiry Knowledge can be documented and assessed by means of a Loughran et al. (2004) Inquiry Content Representation (I-CoRe) developed by the authors through seven inquiry activities mentioned in the last editorial of this Journal, and Inventories collected in interviews. Five high school and college teachers with experience on inquiry-teaching were the subjects of this research. It was observed that all teachers have used inquiry to modify their students’ way of thinking, mainly through question posing but also with open research activities as main tools to promote scientific inquiry. It is interesting to notice that in spite of the fact that inquiry is out of the curriculum, the teachers made use of it to improve their teaching practice. Several verbatim phrases expressed by the teachers are included in this study.
Keywords: pedagogical content knowledge, inquiry, inventory, activities, content representation
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Use of an aquarium pump in spectrophotometric titration. A didactic experiment on the study of the stability of the complexes
Por
Silvia Keli de Barros Alcanfor, Luiz Fabrício Zara, Luciano de Almeida Pinheiro, Jonatas Gomes da Silva, Janaína Moreira de Faria
This work proposes an alternative didactic experiment in order to determine the stability of the complexes that are involved in a spectrophotometric titration of Fe(III) ions with EDTA and 5-sulfosalicylic acid as indicator using a hybrid system in batchwise and in continuous flux, in which a conventional aquarium pump as a propulsion system is employed. The obtained results using this system are according to the literature. However, the use of the aquarium pump in this hybrid system has shown to be really efficient, useful and easy to be used by undergraduate students, and it can be used in any laboratory.
KEYWORDS: formations constant, spectrophotometric titration, aquarium pump, didactic experiment
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