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

Atomic charges within a molecule are frequently referred to in chemistry textbooks and represent the most simplified version of the molecular charge distribution. These charge distributions give insight into molecular polarity, on which many molecular properties of substances depend. Access to atomic charge values ​​requires the use of sophisticated computational methods based on quantum chemistry, which, if accessible, are above the conceptual level for basic chemistry courses (and therefore they would be black box values). In the present work, a conceptually simple method for the calculation of atomic charges that requires knowledge of common topics in chemistry, such as Lewis representations, orbitals and electronegativity, is proposed. Based on the formulation for the calculation of atomic charges, some applications linked to dipole moments, inductive and mesomeric effects, stability of carbocations, acidity of halogenated carboxylic acids, catalytic action of Lewis acids and contribution of lone pairs of electrons to the dipole moment.

De novo protein design is an innovative field with relevant applications in medicine and biotechnology. It involves creating proteins “from scratch,” with amino acid sequences entirely different from those found in nature. This work presents the evolution of the field, from its beginnings with minimalist and rational design in the 1980s to the current use of language models based on deep learning. The main objective is to provide undergraduate and graduate students with an overview of the significant advances in de novo protein design and its connection to protein folding and functional protein development.

In the university educational context, the assessment of the training process frequently falls on the teacher and the prescribed curriculum, with little involvement of the student, thus requiring the transformation of these traditionalist perspectives. Objective: to explore students’ perceptions of the evaluation process carried out by their teachers in professional training courses delivered through virtual environments at a Colombian university. Method: a mixed research approach was adopted, prioritizing quantitative methods. The sample consisted of 65 students from Technological Sciences programs, selected through intentional sampling. Textual data were collected using a questionnaire with open-ended items, which were categorized, quantified, and interpreted through content analysis supported by the open-source software R. Results: the data obtained were organized into 10 categories with subcategories, which revealed that 80% of students perceive that their teachers appropriately assess student learning, although further optimization of these processes is still required in the virtual context. Conclusions: the findings show that students are only partially satisfied with the evaluation practices applied to them; nevertheless, there is a need to improve formative assessment, the assessment instruments, and the methods for certifying the competencies achieved by students.

Objective: to analyze the debate to identify the development of argumentation, critical thinking, deliberation of public affairs and personal and social competencies in 5th grade secondary school students in a private school in Lima, Peru. Methodology: the qualitative approach with descriptive level was used. The information was collected with the focus group technique and the semi-structured interview. The case consisted of two focus groups with a total of 20 participants from the 5th grade of secondary school considering the inclusion criteria. The informants' voices were used as a starting point through the inductive method, coded into categories with Open and Axial Coding. Triangulation was carried out among informants. Results: the debate strategy has been shown to develop critical thinking, argumentation, public affairs and socio-personal skills in students during their basic education. Conclusions: it was concluded that debate promotes critical attitudes, reflection, evaluation and analysis; it fosters argumentative, personal, social, academic and communicative skills; it is evident that public affairs are deeply deliberated, and active citizenship is favored in students.

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Chemistry teaching is dynamic and one way to generate meaningful learning is through its application. For example, organic chemistry is applied to polymerization mechanisms and promotes their understanding. It is very common to find chain mechanisms in books, whether ionic or via free radicals, but this is not the case for polymers that are obtained in step mechanisms. The step mechanisms are different depending on the organic functional groups involved in the polymerization reactions. So, knowledge of organic chemistry is necessary to understand these mechanisms. The mechanisms of polymerization reactions can be a complex topic to understand for many students and apprentices of polymer chemistry. This article details and compares the mechanisms of stage and chain polymerization, evidencing their differences and emphasizes developing reaction mechanisms of some commodity and engineering polymers that are obtained by the step mechanism; PET, Nylon, Thiokol, polyurethane, Bakelite and melamine in a didactic and dynamic way for easy learning.

Plastic pollution has been one of the major socio-environmental problems and, new concerns, are currently being highlighted due to the omnipresence of the so-called microplastics (MP) in different ecosystems. This research paper presents a proposal for an experimental approach to the theme of microplastics and the environment for Chemistry classes in High School, with an initial focus on a bibliographic survey on the subject in the context of basic education. From the survey, it was possible to develop sequences and/or teaching practices in Chemistry correlated to techniques for identifying, characterizing and removing plastic particles and to realize that these practices can enable the insertion of chemical, economic and socio-environmental knowledge connected with the Sustainable Development Goals of the United Nations 2030 Agenda. The bibliographic research and the development of practices on microplastics can open perspectives for basic education teachers/students to know and use them in teaching and learning contexts about plastic pollution and environmental chemistry.

Julien-François Jeannel (1814-1896) was a French physician and pharmacist who studied the assimilation of food in living organisms, particularly calomel; the chemistry of iron sesquioxide; the production of nitrates and nitrites in nature; the phenomenon of supersaturation and its use in crystallization and heat storage; the physical and chemical properties of sodium acetate; and more. He found that food assimilation was preceded by the formation of an emulsion, highly favored by alkaline carbonates, and that Hg(I) was transformed into Hg(II), the action of which was mitigated by albumin and fatty material. In the presence of water and HCl, iron sesquioxide hydrate transformed into iron sesquioxide chloride, ferric chloroxide, Fe₂Cl₃·9Fe₂O₃, highly soluble in water. Jeannel postulated that nitrates and nitrites were formed naturally in the topsoil upon contact with air, that it was possible to feed plants with suitable mineral solutions providing them with the solid elements needed to grow, and that plants vegetated much better in pure sand than in loam. Jeannel demonstrated that supersaturation and crystallization were not caused by particles floating in the air but by seeding with crystals of the same compound or solid bars. He also suggested that sodium acetate could be used to store solar energy.

A didactic sequence is presented with the aim of enabling students to integrate the concepts of enthalpy, entropy, chemical reaction, and balance into their daily lives through the Project-Based Learning (PjBL) strategy. The strategy was applied in a group of the High School. A project was assigned to each team of 4-5 students. The projects developed were the obtaining of a white bioglue for home consumption, the neutralization of stomach acidity and the oxidation of hydrocarbons. At each stage of the project, students took responsibility for their own learning and the teacher served only as a guide. Before and after the implementation of the strategy, a questionnaire with multiple-choice and open-ended questions was applied. Based on the results, an improvement was observed in the correlation of the concepts of enthalpy, entropy and equilibrium with chemical reactions and their importance in everyday life. Also, it was evidenced that the alternative conceptions of the concepts of temperature, heat, work, enthalpy, entropy, spontaneity and chemical equilibrium were reduced, when analyzed from chemistry in context.

In Mexico, the regulatory framework mandates that industrial sectors engaging in high-risk activities must submit an environmental risk assessment for specific scenarios such as spills, leaks, fires, or explosions. However, this requirement does not consider the potential impacts that may arise from the daily operations of industries that continuously release toxic substances into the atmosphere. While air quality assessments are conducted based on maximum permissible limits of criteria pollutants aimed at protecting public health, there are no instruments in place that require industry to conduct a risk analysis for the health of the population exposed to atmospheric pollutants that they themselves emit. In this work, a methodological proposal is presented to teach the evaluation of these risks, which begins with the theoretical framework, the United States Environmental Protection Agency (EPA) risk assessment procedure and common indices for risk communication. The evaluation process includes a case study that uses information from the Pollutant Release and Transfer Registers (PRTR), as well as the California Air Resources Board’s Consolidated Table. In addition, other references are provided that show case studies developed with this methodology, which have allowed the identification of sources and substances that could represent a potential risk to human health and the environment. This work can serve as a guide for the development of teaching materials and environmental legislation on the subject.