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

A experimentação em química é fundamental para a construção de conceitos que permitam ao estudante compreender o mundo, sendo ação facilitadora do processo de ensino e aprendizagem. Esse artigo apresenta um projeto de estudo que propõe discutir o conceito de indicadores ácido-base, distinguindo colorimetricamente produtos do cotidiano dos estudantes, a partir do uso de indicadores naturais de pH em aulas experimentais de química no Ensino Médio. Os legumes utilizados foram repolho roxo, beterraba, cebola roxa e berinjela, os quais apresentam alto teor de antocianinas. Esta ação reforça os princípios da química verde de sustentabilidade e meio ambiente, não gerando resíduos tóxicos, promovendo a discussão de conceitos fundamentais da química, através de uma abordagem motivadora, e fortalecendo o processo de ensino e aprendizagem

As atividades experimentais representam um papel importante no processo de ensino e aprendizagem de Química, porque motivam os estudantes e promovem a correlação entre atividades desenvolvidas em sala de aula e situações cotidianas. Baseado neste contexto, este trabalho apresenta uma proposta experimental para a síntese de FeSO4.7H2O utilizando palha de aço, visando trabalhar conceitos como estequiometria, reações de óxido-redução, lei dos gases ideais, interações intermoleculares, solubilidade, volumetria e equilíbrios em meio aquoso, destacando os equilíbrios ácido-base, de precipitação e de complexação. O experimento é direcionado tanto para estudantes do ensino médio, como para alunos de graduação, visando auxiliá-los no desenvolver conceitos importantes na química geral, química inorgânica e química analítica. Em contrapartida, a atividade também poderá auxiliar na reflexão sobre reaproveitamento de materiais.

La formación de profesionales con un perfil interdisciplinario como el del científico forense es un reto educativo que implica repensar los principios didácticos de disciplinas científicas con una identidad más claramente definida, como es el caso de la química. La construcción de un modelo de enseñanza ad hoc que incluya estrategias didácticas diseñadas para el contexto forense es, pues, tarea indispensable. En este trabajo se describe el diseño, la puesta en práctica y los resultados del Taller interdisciplinario para la resolución de casos forenses, una estrategia de enseñanza basada en la resolución de problemas que busca contribuir a la formación de científicos forenses y que, además, es botón de muestra del potencial que el tema forense tiene como un contexto propicio para la ensenanza de las ciencias.

O trabalho apresenta uma análise sobre a construção das teorias ácido-base no século XX, mais especificamente as participações de S.A. Arrhenius, J.N. Bronsted, T.M. Lowry e G.N. Lewis. Ao longo da revisão historiográfica confrontamse as visões ingênuas da natureza da ciência, a fim de melhor refletir sobre o papel do cientista na ciência. A leitura proporcionará um repensar sobre a importância da história da química na sala de aula.

Part II of this two-part article on the history of the teaching of qualitative analysis covers the hydrogen sulfide problem, the debates over why and how qualitative analysis should be taught to undergraduate chemistry majors, and comments on its eventual demise. It also contains the references for both parts.

Part I of this two-part article on the history of the teaching of qualitative analysis to undergraduate chemistry majors covers the origins of the course, its theoretical rationale, the impact of spot analysis and tailored organic reagents, and its transformation from a macro scheme to a semi-micro scheme.

Electronic substituent effects are usually classified as inductive (through σ-bonds) and resonance effects (via π-bonds). The alkyl group has been usually regarded as aσ -electron donor substituent (+I effect, according to the Ingold’s classification). However, a σ-withdrawing, π-donor effect (-I + R pattern) allows explaining the actual electron-withdrawing behavior of alkyl groups when bound to sp³ carbon atoms as well as their well-known electron-releasing properties when attached to sp² or sp atoms. Alkyl substitution effects on several molecular properties (dipole moments, NMR, IR, and UV spectra, reactivity in gas phase and solution) are discussed.

Recent scholarship in the interdisciplinary field of the learning sciences has focused on the ways that young people use digital tools to connect learning experiences across different settings and over time. Two aspects stand out in this research: (i) the potency of youth agency in creating new activities, communities, and pathways for interest-related pursuits and (ii) the ways that peers, adults, and different sociocultural contexts afford and constrain opportunity. These contexts, or settings, include peer groups and families; schools, neighbourhoods and cities, and also nationwide infrastructures that foster connections between school-based and out-of-school learning. The articles in this special issue of Digital Education Review shed light on these topics and advance our understanding of the theories that deal with learning across various settings and times, and how to promote more equitable youth learning across these settings.

This study analyzes how agricultural income insecurity has affected the creation of productive enterprises in the social and solidarity economy of Ecuador. It draws on several studies of the main causes of agricultural income insecurity and their subsequent evaluation, the status of peasant agriculture, and the historical evolution of social and solidarity economy enterprises. It accompanies this bibliographical review with field research focused on actors involved in productive enterprises – represented by peasant organizations from the social and solidarity economy based in the northwestern part of Pichincha province (Ecuador) – through a survey and several meetings to identify the reasons behind their ventures and confirm whether they conform with the social and solidarity economy policy. The results allow recognition of new forms of entrepreneurship through associativity, as well as providing information to government entities for future policies that encourage the development of this sector of the economy.

This paper estimates the spatial or geographic effects of employment, income and production value of eleven mining centers upon the share of employment of the primary, secondary and tertiary sectors from the geographic areas wherein these centers are located. Based upon a Spatial Durbin Model, SDM, the main estimation results points outs that the ‘direct effects’ of the income or mining output generated in the geographic areas wherein the mining centers are located upon the share of employment in the primary, secondary and tertiary sectors of the same areas were statistically significative for most of the estimations (about 69,4% of them). Contrarily, these effects for the share of formal employment of the mining centers were not statistically significative for most of the estimations (about 61,1% of them). However, the ‘indirect’ geographic or spillovers effects of such an employment were significative particularly for the share of the informal employment of the secondary, tertiary and primary (in that order). These employment geographic spillovers effects has implied that changes in the formal employment share in the mining sectors were associated to changes in the informal employments shares of the secondary, tertiary and primary (in that order) of the geographic areas close to de mining production centers. The indirect effects of income and production value in the production centers were not significative.