Navegando por Assunto "Chemistry"

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Acesso aberto (Open Access)
The ceramic artifacts in archaeological black earth (terra preta) from Lower Amazon Region, Brazil: chemistry and geochemical evolution
(Instituto Nacional de Pesquisas da Amazônia, 2004-09) COSTA, Marcondes Lima da; KERN, Dirse Clara; PINTO, Alice Helena Eleotério; SOUZA, Jorge Raimundo da Trindade
This paper carried out a chemical investigation of archaeological ceramic artifacts found in archaeological sites with Black Earth (ABE) in the Lower Amazon Region at Cachoeira-Porteira, State of Pará, Brazil. The ceramic artifacts, mostly of daily use, belong to Konduri culture (from 900 to 400 years BP). They are constituted of SiO2, Al2O3, Fe2O,3, Na2O and P2O5; SiO2 and Al2O3 together add up to 80 % and indicate influence of acid rocks, transformed into clay minerals basically kaolinite. The relative high contents of P2O5 (2.37 % in average) come out as (Al,Fe)-phosphate, an uncommon fact in primitive red ceramics, but found in some roman and egyptian archaeological sites. The contents of the trace elements are similar or below the Earth's crust average. This chemical composition (except P2O5) detaches saprolite material derived acid igneous rocks or sedimentary ones as the main raw material of the ceramics. The contents of K, Na and Ca represent the feldspars and rock fragments possibly introduced into saprolitic groundmass, indicated by mineralogical studies. The presence of cauixi and cariapé as well as quartz sand was confirmed by optical microscope, SEM analyses and by the high silica contents of ceramic fragments. Phosphorus was possibly incorporated into groundmass during cooking of foods, and ABE soil profile formation developed on yellow Latosols. The raw materials and its tempers (cauixi, or cariapé, feldspar, crushed rocks, old ceramic artifacts and quartz fragments) are found close to the sites and therefore and certainly came from them.
Acesso aberto (Open Access)
Motivação e imaginação no contexto da prática pedagógica e na aprendizagem em química
(Universidade Federal do Pará, 2023-06-02) SANTOS, Priscilany Cavalcante dos; PARENTE, Andrela Garibaldi Loureiro; http://lattes.cnpq.br/0934892702963831; https://orcid.org/0000-0003-3396-700X
The objective of this research is to understand how comprehensive and/or creative chemistry learning is subjectively configured, in the context of investigative practices. The construction of the research theoretical model was based on the principles of Qualitative Epistemology, proposed by González Rey (2005). Such principles relate to knowledge production processes, highlighting the constructive-interpretive character, the interactive character (dialogue) and the singularity. For the construction of the information, instruments such as informal conversations, interviews, videos and images of school actions, written records and the technique of completing sentences were used, based on the hypotheses elaborated in the course of the research. Max's case study and the analysis of the pedagogical practice made it possible to elaborate principles with the intention of contributing to the students' learning. Such principles include curiosity as a guiding principle to encourage imagination, investigative practice as a promoter of imagination and the creation of a pedagogical strategy in teaching and learning in chemistry. In addition, the construction of a pedagogical practice that favors learning includes spaces for dialogue, partnership relationships and knowledge production that allow understanding the student's motivations in the context of learning as a subjective production.
Acesso aberto (Open Access)
Temas transversais da química ambiental e história em quadrinhos como ferramentas pedagógicas para o ensino de ácidos e bases
(Universidade Federal do Pará, 2020-09-28) CRUZ, Erivan Sousa; ROCHA , Edson José Paulino da; http://lattes.cnpq.br/2313369423727020; PEREIRA, Simone de Fátima Pinheiro; http://lattes.cnpq.br/6059412003152989
Science teaching has required methodological strategies capable of dealing with a huge range of content. In order to train critical citizens in the classroom, it is necessary to support different models of knowledge presentation. The present research had as main objective, to improve the teaching-learning process in the teaching of Chemistry using as transversal educational themes of Environmental Chemistry and the Comic Magazine. The theme chosen was “Acids and Bases” and their relationship with environmental phenomena, such as acid rain. The software chosen was Hagáquê, a free comic book creator and Paint Shop Pro, an image editor. Polling questionnaires were used during traditional expository classes, the students' answers were treated with the Excel program. The application of the methodology that included, as the main core, the comic books, was carried out in two stages: the first using a traditional class and the second using the transversal theme Acid Rain and the comic book. The research made it possible to ascertain the improvement in the teaching and learning process assessed through questionnaires that demonstrated an increase in the number of correct answers to objective questions before and after the use of the alternative methodology in two classes of degree in chemistry (2016 and 2019) with an average of around 30%. Most students answered that they have “great interest” in the general chemical discipline and all students concluded that the use of environmental themes and comic books can help in the teaching-learning process.
Acesso aberto (Open Access)
The Belterra Clay On The Bauxite Deposits Of Rondon Do Pará, Eastern Amazon
(Sociedade Brasileira de Geologia, 2018-09) NEGRÃO, Leonardo Boiadeiro Ayres; COSTA, Marcondes Lima da; POELLMANN, Herbert
Bauxite deposits in the Amazon region are commonly covered by yellowish clays which can reach up to 25m thick, known as Belterra Clay (BTC). In Rondon do Pará, Eastern Amazon, BTC is 13m thick and covers world-class bauxite reserves. Three pilot bauxite mines were investigated in Rondon do Pará for an initial characterization of the local BTC. In discordant contact with the lateritic profile, the BTC has reddish brown colors at its base to ocher tones towards the top. It has a massive structure with silt-clayey texture and nodular bauxitic fragments at its base. Rietveld mineral quantification of the material attests that it is dominated by kaolinite, with goethite, gibbsite, hematite, anatase and residual quartz. The thermal behavior of the material also confirms its mineralogical composition. Kaolinite is of low structural order, which was considered the main difficulty in the application of the Rietveld method. Goethite has up to 33 mol% of Al. As observed by scanning electron microscopy (SEM), the minerals represent pseudo-hexagonal crystals measuring from 150 to 700 nm. The BTC in the studied area is correlated to BTC on others bauxitic deposits of the Amazon region, suggesting this material experienced the same genesis and geological evolution, probably during the Pliocene.