Chemical equilibrium and Newton's third law of motion: Ontogeny/phylogeny revisited

Abstract

Evolution of the concept of chemical equilibrium has been strongly influenced by Newtonian mechanics. Even in the late nineteenth century scientists viewed chemical equilibrium as resulting from an equality of the contending forces, that is, the forward and the reverse reactions. The main purpose of this article is to show that freshman students conceptualize the rates of the forward and reverse reactions in chemical equilibrium as forces, perhaps in the same sense as used in the evolution of the concept of chemical equilibrium and student misconceptions about Newton's third law of motion. Results obtained show that at least some students consider the forward and reverse reactions as a sort of chemical analogue of Newton's third law of motion. Based on this interpretation, it is plausible to hypothesize that student conceptualization of the forward and reverse reactions as forces is ontogenetically (Piaget & Garcia, 1983) a step towards the deeper understanding of a dynamic chemical equilibrium, leading to a progressive 'problemshift' (Lakatos, 1970).In spite of the eommonalities between psychogenesis and the history of science, it is important to point out that ontogenesis is not an exact and detailed recapitulation of phylogenesis. Results obtained in this study and their interpretation are important, as they help us to anticipate student utilization of Newton's third law in understanding chemical equilibrium, before the dynamic nature of equilibrium is understood.

Facilitating conceptual change in students' understanding of electrochemistry

“…There is a relationship between the process of theory development by scientists and an individual's acquisition of knowledge (Kitchener 1986, Piaget and Garcia 1989, von Glasersfeld 1989, Duschl 1990, Chinn and Brewer 1993, Niaz 1995b). 2.…”

Constructivism: Defense or a Continual Critical Appraisal A Response to Gil-Pérez et al.

“…'s presentation of the 'student as a scientist' metaphor (p. 560) leads to a 'straw man' as hardly any science educator would perhaps accept the thesis that students work/learn as scientists (ontogenesis recapitulates phylogenesis). Science educators, psychologists and philosophers would perhaps agree that there is a limited relationship between the process of theory development by scientists and a students' acquisition of knowledge, i.e., a 'developing scientist' (Chinn & Brewer 1993, Duschl 1990, Kitchener 1987, Piaget & Garcia 1989, Niaz 1995, von Glasersfeld 1989. Although the authors endorse the role of students as novice researchers, it appears that under certain situations they do visualize the student as a scientist, an aspect that has been critiqued previously (Marín et al 1999, Pozo & Gómez Crespo 1998 and the following corroborates our claim: "The proposal to organize pupils' learning as a knowledge construction corresponds to the first situation [solving routine problems], that is to say, to an oriented research, in fields very well known by the 'research director' (the teacher) .…”

El principio de Le Chatelier como regla cualitativa: un obstáculo epistemológico en el aprendizaje del equilibrio químico

“…Esta confusión se refuerza en algunos casos mediante la explicación del principio con la ayuda de analogías de tipo mecánico y que toman, al igual que el propio Le Chatelier (1888), la tercera ley de Newton como referencia básica: comportamiento de un muelle por acción de una fuerza (Nekrásov, 1981); reacción de un tubo de pasta de dientes por compresión sobre uno de sus extremos (Kotz y Purcell, 1987); compresión lateral de un globo que contiene una pequeña cantidad de aire (Bailar et al, 1983). En este sentido, Níaz (1995) establece un paralelismo entre la influencia que ha tenido la mecánica newtoniana tanto en la evolución histórica del concepto de equilibrio químico como en las ideas de los alumnos relacionadas con la cinética de reacción y el desplazamiento del equilibrio. Finalmente, señalaremos que otras palabras como sistema, variable, factor o punto de equilibrio pueden no conocerse con precisión por parte de los alumnos.…”