Educacion Quimica最新文献

James Wei, a professor at the Department of Chemical Engineering-MIT, used the paradigm concept in 1988, introduced by T. Kuhn, to characterize the steps of evolution of the Chemical Engineering. Wei identified three periods: the pre-paradigmatic, a first paradigm which he relates to the publication of the text ‘Principles of Chemical Engineering’, and a second paradigm associated with the text: ‘Transport Phenomena’, by Bird, Stewart and Lightfoot, in 1960. Wei's paradigms are reductionistic as well as limited and need to be expanded and updated. In this work three steps are identified: the pre-paradigmatic, the paradigm of Unit operations, and the paradigm of the Science of Chemical Engineering. Reference is made to the new frontiers of Chemical Engineering and to the requirement to include new academic disciplines and new techniques of teaching and learning.

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 a σ-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.

Experimental activities play an important role in the teaching and learning process in chemistry, because it motivates students and promotes the correlation between the activities in the classroom and everyday situations. Based on this context, this work presents an experimental proposal for the synthesis of FeSO₄.7H₂O using steel wool, aiming at the presentation of concepts such as stoichiometry, oxidation‐reduction reactions, the ideal gas law, the intermolecular interactions, solubility, volumetry and equilibrium in aqueous medium, emphasizing the acid‐base, precipitation and complexation equilibria. The experiment is designed for both high school students and undergraduate students, with the goal of helping them to develop key concepts in General Chemistry, Inorganic Chemistry and Analytical Chemistry. Moreover, activity may also assist in reflection on reuse of materials.

Training professionals with an interdisciplinary profile such as forensic scientist is an educational challenge which involves rethinking didactic principles from more clearly defined scientific disciplines, such as chemistry. Thus, constructing an ad hoc teaching model that includes didactic strategies specifically designed for the forensic sciences is an indispensable task. This paper describes the design, implementation and results from the Interdisciplinary Workshop for the Resolution of Forensic Cases, a problem-based teaching strategy that seeks to contribute to the training of forensic scientists; furthermore, this example highlights the potential for teaching sciences in context that the field of forensic sciences presents.

This instructive experiment aims to show the importance of validation on analytical method in the study of sulfate chemistry in the environment. Even though the method of sulfate determination has pointed out satisfactory linearity, sensitivity, limit of detection and quantification, and precision in aqueous matrices, this experiment showed that it has low accuracy for complex aqueous matrices, such as lagoon and estuary. Therefore, the method is only recommended for aqueous matrices with little complexity, such as drinking water. The students could were able to understand the validation concepts and grasp the importance of certifying the adequacy of the chemical method, which guarantee the quality of the results and consequently accurate conclusions. Furthermore, the use of the fundamentals of statistic in chemical analysis as well as the application of software for data processing provided the students with an opportunity to integrate computer analysis with theory and practice.

Experimentation in chemistry is fundamental in order to create concepts that allow the students to understand the world, thus facilitating the teaching and learning processes. This paper presents a study project, which proposes the discussion of the concept of acid‐base indicators, distinguishing colorimetrically products present in the everyday lives of students, with the use of natural pH indicators in experimental chemistry classes in High School. In this regard, the vegetables purple cabbage, beet, red onion and eggplant, which have high contents of anthocyanins, are used. In this way, the principles of Green Chemistry aimed at sustainability and protecting the environment are emphasized, avoiding the generation of toxic residues. Thus, the discussion of the fundamental concepts of chemistry is promoted through an innovative approach, strengthening the teaching and learning processes.

We can find an extensive list of research articles aimed to identify structure of matter representations in people belonging to several levels in the educative system. Students’ learning of the explanation of macroscopic phenomena in terms of discrete and microscopic models constitutes one of the purposes of secondary and university education. The corpuscular model is essential to explain, e.g., the differences among the three states of matter, their properties and the (physical or chemical) changes they may undergo. Research has shown that although students easily accept this corpuscular model and some of its terminology, they do not use it spontaneously. This article presents an inquiry on representations about structure of the three states of matter in university students together with an evaluation of their use for combinations of states, showing that also in this level and for students belonging to Introductory Chemistry courses, the discrete model of matter accepted by the scientific community is dominant only for gases but not for solids and liquids.

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.