Chemistry Textbook Approaches to Chemical Equilibrium and Student Alternative Conceptions

In the field of chemistry there has been considerable interest in discovering the reasons why many students have great difficulty in successfully developing a scientifically accepted understanding of chemical equilibrium. Research projects influenced and inspired by constructivism have been invaluable for identifying alternative conceptions that may turn into obstacles to meaningful learning of fundamental ideas regarding chemical equilibrium. Research findings provide evidence that misunderstandings of and related to chemical equilibrium are widespread at various levels of education, including prospective chemistry teachers. Language used in textbooks may give rise, or reinforce student alternative conceptions and research findings point to a direct relationship between language used in textbooks and some of the alternative conceptions students develop at various levels of school chemistry. Some of the students’ alternative conceptions already identified, and available in literature, were the basis of an instrument devised to analyse chemistry textbooks used in secondary and tertiary education. This paper presents and discusses typical problematic language found in student textbooks in the light of students’ current frameworks of understanding as described in literature

Phytotoxicity of lead on Lactuca sativa: effects on growth, mineral nutrition, photosynthetic activity and oxidant metabolism

Pb (lead) contamination in water and soils is increasing and its accumulation in plants may have serious deleterious consequences for environment and human health. Lead effects on plants still remain unclear and, therefore, a selection of Pb sensitive parameters used as biomarkers is required for improvement within the scope of Ecological Risk Assessment. In this study Lactuca sativa L. plants were exposed to Pb to contaminated irrigation solutions (12.5 mg l-1 and 125 mg l-1) for 15 days. Orthogonal analyses (time vs. Pb concentration vs. organ) were carried out after one, seven and fifteen days to elucidate about the effects of this element in plants. During exposure, plant growth, nutritional imbalance, water content, soluble protein content, lipid peroxidation (malondyaldehyde accumulation) and photosynthesis (chlorophyll contents and PSII fluorescence) were assessed in order to find the most adequated parameters for further studies in under realistic environmental conditions. Morphological and growth parameters showed decreases of root and shoot growth and alterations in root branching pattern. Biochemical parameters showed nutritional imbalance mostly concerning Pb, K (potassium) and Fe (iron) contents, changes in chlorophyll content and chlorophyll a:b ratio and malondyaldehyde accumulation. Therefore, such biochemical parameters may be used/ recommended as assessment parameters complementary to morphologic ones (e.g. shoot and root lengths) both in toxicological tests and further studies under realistic environmental conditions.publishe

Questions in Science textbooks: development and validation of a checklist

Questões são enunciadas que requerem uma resposta refletida e que desempenham diversas funções educativas, incluindo o despoletar novas aprendizagens. Neste caso, o seu uso enquadra-se na Aprendizagem Baseada na Resolução de Problemas (ABRP, do inglês, Problem-Based Learning, PBL), que coloca o aluno no centro dos processos de ensino e aprendizagem, atribuindo-lhe um papel ativo na aprendizagem de novo conhecimento. Atendendo à influência que os manuais exercem nas práticas de ensino, a questão que se coloca é a de saber em que medida as questões incluídas nos manuais escolares de Ciências podem fomentar um ensino orientado para a ABRP. Neste texto, descrever-se-á o processo de construção e validação de uma grelha de análise de questões incluídas em manuais escolares de Ciências com essa finalidade, apresentando-se não só essa grelha, mas também, a título ilustrativo, uma aplicação da mesma a um tópico de Ciências, 8º ano, abordado nas duas disciplinas desta área.Questions require a thoughtful answer and can play diverse educational roles, such as stimulating the learning of new knowledge, as is the case in Problem-Based Learning (PBL) contexts. In this context, the student is placed at the center of the teaching and learning processes and plays an active role in the learning of new knowledge. Bearing in mind the influence that textbooks exert on teaching practices, it is worthwhile questioning to which extent questions included in school science textbooks promote a PBL oriented teaching approach. This paper describes the development and validation of a checklist for analyzing the questions included in science textbooks. After introducing the checklist, an example of its application to a science unit assigned to two junior high school science courses (8th grade) is given, approaching the two disciplines in the area

Genetic variability in the tolerance of natural populations of Simocephalus vetulus (Müller, 1776) to lethal levels of sodium chloride

Using several clonal lineages of Simocephalus vetulus (Cladocera, Daphniidae) as a random sample, we investigated the genetic component of the halotolerance of one brackish and two freshwater populations of this littoral filter feeder. We hypothesized that genotypes from the brackish population were more tolerant than freshwater ones, via adaptation to local environmental conditions. Clonal identity was established by a cost-effective molecular fingerprinting technique (microsatellite-primed polymerase chain reaction (MSP-PCR)). Two distinct methodologies were used to assess cladoceran sensitivity to syntheticgrade sodium chloride (NaCl): (i) standard 48-h acute assays and (ii) 12-h survival time (ST) trials. No correlation was found between acute EC50 and ST values. The sensitivity of brackish and freshwater clones was comparable in terms of acute EC50 (varied from 2.28 to 3.83 g.Lx1). On the contrary, genetically determined differential tolerance to NaCl among populations was found for ST: all brackish genotypes, except one, were more resilient (ST>120 min) than freshwater clones (ST<120 min). Bearing in mind that these results were obtained with isolates from the extant population, it is surprising that the range of acute sensitivity of the freshwater and brackish genotypes was similar, and that the only difference between them was the ability of brackish clones to survive longer under high salinity stress (6 g.Lx1, in ST trials). We must conclude that the effect of salinity (original environment context) on the selection of genotypes was weaker than we had expected and than other authors have shown for other stressors.publishe

Competitive outcome of Daphnia-Simocephalus experimental microcosms: salinity versus priority effects

Competition is a major driving force in freshwaters, especially given the cyclic nature and dynamics of pelagic food webs. Competition is especially important in the initial species assortment during colonization and re-colonization events, which depends strongly on the environmental context. Subtle changes, such as saline intrusion, may disrupt competitive relationships and, thus, influence community composition. Bearing this in mind, our objective was to assess whether low salinity levels (using NaCl as a proxy) alter the competitive outcome (measured as the rate of population biomass increase) of Daphnia-Simocephalus experimental microcosms, taking into account interactions with priority effects (sequential species arrival order). With this approach, we aimed to experimentally demonstrate a putative mechanism of differential species sorting in brackish environments or in freshwaters facing secondary salinization. Experiments considered three salinity levels, regarding NaCl added (0.00, 0.75 and 1.50 g L(-1)), crossed with three competition scenarios (no priority, priority of Daphnia over Simocephalus, and vice-versa). At lower NaCl concentrations (0.00 and 0.75 g L(-1)), Daphnia was a significantly superior competitor, irrespective of the species inoculation order, suggesting negligible priority effects. However, the strong decrease in Daphnia population growth at 1.50 g L(-1) alleviated the competitive pressure on Simocephalus, causing an inversion of the competitive outcome in favour of Simocephalus. The intensity of this inversion depended on the competition scenario. This salinity-mediated disruption of the competitive outcome demonstrates that subtle environmental changes produce indirect effects in key ecological mechanisms, thus altering community composition, which may lead to serious implications in terms of ecosystem functioning (e.g. lake regime shifts due to reduced grazing) and biodiversity

Educação em ciências e sustentabilidade na terra : uma análise das abordagens propostas em documentos oficiais e manuais escolares

Às Metas de Desenvolvimento do Millennium (MDM), que reflectem as aspirações partilhadas e negociadas a nível global, estão associados diversos indicadores de que se destaca o indicador de desenvolvimento humano (IDH). Não pretendendo evidenciar uma imagem completa de estados de desenvolvimento humano, o IDH configura-se como um barómetro que, facultando medidas de variações de bem-estar humano e não se limitando a ponderar rendimentos, permite comparar progressos em diferentes países e regiões do mundo. É um indicador composto que pondera três dimensões: “rendimento, educação e saúde” (UNDP, 2005, p.21). O último relatório do PNUD (Programa das Nações Unidas para o Desenvolvimento) revela enormes assimetrias e diferenças insustentáveis no acesso à educação, com cerca de 115 milhões de crianças sem acesso à mais elementar educação básica (UNDP, 2005). A maioria dessas crianças habita no sul da Ásia e na África, em países a sul do deserto do Sahara. O mesmo relatório revela, igualmente, que a duração média da frequência escolar aponta para o aumento do fosso entre países ricos e pobres (embora as diferenças no ensino básico elementar tendam a diminuir), como evidenciam as expectativas médias de escolarização de crianças nascidas actualmente num país africano (Moçambique) versus num europeu (França), respectivamente 4 e 15 anos (UNDP, 2005). Assim, a educação superior está ainda longe de constituir um direito, continuando antes a configurar-se como um privilégio de quem pode custeá-la, ou seja, maioritariamente um privilégio de cidadãos de países ricos. Como salientam as próprias Nações Unidas, “Estas desigualdades educativas de hoje são as desigualdades sociais e económicas globais de amanhã” (UNDP, 2005, p.24)

Chemistry Textbook Approaches to Chemical Equilibrium and Student Alternative Conceptions

In the field of chemistry there has been considerable interest in discovering the reasons why many students have great difficulty in successfully developing a scientifically accepted understanding of chemical equilibrium. Research projects influenced and inspired by constructivism have been invaluable for identifying alternative conceptions that may turn into obstacles to meaningful learning of fundamental ideas regarding chemical equilibrium. Research findings provide evidence that misunderstandings of and related to chemical equilibrium are widespread at various levels of education, including prospective chemistry teachers. Language used in textbooks may give rise, or reinforce student alternative conceptions and research findings point to a direct relationship between language used in textbooks and some of the alternative conceptions students develop at various levels of school chemistry. Some of the students’ alternative conceptions already identified, and available in literature, were the basis of an instrument devised to analyse chemistry textbooks used in secondary and tertiary education. This paper presents and discusses typical problematic language found in student textbooks in the light of students’ current frameworks of understanding as described in literature

Encurtando Distâncias entre Escolas e Cidadãos: Enredos Ficcionais e Educação em Ciências

Argumenta-se, em várias instâncias, que a educação em ciências é necessária para criar condições de participação activa em sociedades democráticas, enfatizando-se a rapidez dos desenvolvimentos científicos e tecnológicos e suas consequências em aspectos básicos da vida dos cidadãos. Reconhecem-se propósitos diversos dos de currículos tradicionais, que se centram na transmissão de corpos de conhecimentos aproblemáticos, e propõem-se inovações. Estas requerem intervenções apropriadas em formação de professores, inicial e continuada, por força do papel importante que desempenham na implementação de currículos formais e da tendência para reproduzirem modelos de actuação a que foram expostos na sua formação. Assim, apresenta-se um projecto integrado numa licenciatura de formação inicial de professores, que culminou numa exposição temática aberta ao público, em que se interligaram conteúdos académicos com objectos e equipamentos que se utilizam/usufruem no dia-a-dia. Apresentam-se e discutem-se aspectos de ensino das ciências e reformas educativas, de literacia e educação científica e formação de professores, relevantes no contexto institucional em que o projecto se desenvolveu. Incluem-se secções onde se descreve o projecto, se apresentam e se discutem dimensões e resultados de avaliação, conclusões e implicações para o ensino das ciências e para a formação de professores

Protecçao ambiental e práticas quotidianas individuais e colectivas

Nesta comunicaçao, referindo os programas 3E's (resíduos sólidos urbanos), apresentam-se as características gerais dos programas SAFra (saúde/ambiente/fitofarmacêuticos - resíduos agrícolas) e ERA (energías renováveis e ambiente), que visam estimular práticas quotidianas, individuais e colectivas, de protecçao ambiental. Estes programas de intervençao social diversificada consubstanciam-se em acçoes protagonizadas por um grupo de estudantes, designado EQOFAR (Estudantes de Química Orgânica de Farmácia: Acçao/Reacçao), interrelacionam-se com a disciplina de Química Orgânica da licenciatura de Ciências Farmacêuticas, da Universidade de Coimbra. As metodologias adoptadas para fomentar o desenvolvimento de compêtencias científicas dos estudantes EQFAR, as intervençoes comunitárias dos programas desenvolvidos pelo grupo e a introduçao deste tipo de práticas de ensino e de aprendizagem, em que se aliam contextos formais e nao-formais, pretende-se contribuir para impulsionar a construcçao activa de conhecimento, que permita aprofundar e ampliar compêtencias, incentivando-os a explorar outras vias de desenvolvemento pessoal e social, bem como de desenvolvimento e enquadramento profissional futuro