Resumo

NIAZ, Mansoor  e  MONTES, Luis A.. Understanding stoichiometry: Towards a history and philosophy of chemistry. Educ. quím [online]. 2012, vol.23, suppl.2, pp.290-297. ISSN 0187-893X.

Objectives of this study are: a) Develop a theoretical framework based on history and philosophy of chemistry (HPC); b) Facilitate high school (grade 10) students' understanding of stoichiometry. Study is based on two intact sections of high school students (10 grade, 15-16 year old). Control group instructor used the traditional strategy in which laws of definite and multiple proportions are defined as definitive, irrefutable and applied in the classroom as algorithms. Experimental group instructor used a dialectic constructivist strategy based on the presentation of hypothetical experimental data leading to cognitive conflicts and a critical confrontation of different propositions. Both groups of students were tested on a 6 item test of stoichiometry (1-2 algorithmic and 3-6 conceptual items), after the topic had been taught. Experimental group performed better than the control group, not only on algorithmic items but also items requiring conceptual understanding. Differences in student performance on Items 1, 3, 4 and 5 were statistically significant. HPC perspective developed in this study leads to a critical evaluation of the laws of definite and multiple proportions and their role in chemistry education. Emphasizing these laws as irrefutable, inevitably leads to the memorization of algorithms and formulae in learning stoichiometry.

Palavras-chave : history; philosophy of chemistry; stoichiometry; teaching strategies.

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