Ourides Santin Filho

Experimentos mentais e suas potencialidades didáticas

A review of some articles on thought experiments shows that the use of these tools as resources seems to be very useful in understanding some phenomena that are very difficult to be observed in a real laboratory. In this paper we present an analysis and discussion about the very characteristics of though experiments as a potential instrument for physics teaching.

Determinação da entalpia de vaporização de líquidos pelo método do isoteniscópio de Smith e Menzies

This article proposes an experimental procedure to determine the enthalpy (and entropy) of vaporization of organic liquid compounds, by the Smith-Menzies (isoteniscope) method. The values of vapor pressure at different temperatures were obtained and ΔvH (and ΔvS) were graphically determined, using the Clausius-Clapeyron equation. The results for diethyl-ether, propanone, ethanol and n-hexane are in very good agreement with those from literature. A historical and thermodynamic discussion on equations that correlates vapor pressures and temperature precedes the experimental proposition.

A intermediação da noção de probabilidade na construção de conceitos relacionados à cinética química

In this work we analyze the way that high school students appropriate the concepts and models related to Chemical Kinetics, mainly the kinetic model of collision between particles in chemical reactions (Collision Theory Model). This investigation was based on the studies of Piaget and Inhelder, of Piaget, Jun and Fischbein, who have analyzed if young students exhibit some kind of probabilistic thinking. The methodology was based on pre and post-tests, questionnaires and on interviews. Analysis of these documents showed how the students deal with concepts about probability and how they correlate these concepts with the particle collision kinetic model in Chemistry.Resumo: Este trabalho procurou identificar como estudantes do Ensino Medio se apropriam de conceitos e elaboram determinados modelos inseridos em cinetica quimica, especificamente o modelo cinetico de colisao de particulas numa reacao (Teoria das Colisoes). Esta analise e as reflexoes que a seguiram foram baseadas, sobretudo, nos estudos realizados por Piaget, Piaget e Inhelder, Jun e Fischbein. Utilizamos como documentos as transcricoes das entrevistas (pre e pos-testes) realizadas individualmente com cada aluno. Inicialmente, os estudantes foram entrevistados (pre-testes) com o intuito de identificar a familiaridade com a nocao de evento probabilistico ou aleatorio. Numa segunda etapa (pos-testes), esse conhecimento (ou a ausencia parcial/total dele) foi posto a prova numa tentativa de se estabelecerem relacoes com um conteudo especifico da Quimica (Teoria das Colisoes). Os resultados obtidos apontam para grandes discrepâncias entre o modelo cinetico de colisoes elaborado pelos estudantes e aquele cientificamente aceito. Palavras-chave: Probabilidade. Cinetica quimica. Teoria das colisoes.