Сп. „Химия“, книжка 2/2019

Curriculum Matters

Development of a Lesson Plan on the Teaching of Module „Water Conductivity“

Резюме. The writing of this article is done in light of the need dictated by contemporary developments in the field of chemistry teaching which shape new facts and challenges in the teaching of chemistry and in particular about the subject of “Water Conductivity.” The lesson plan created about “Water Conductivity” aims to create a technologically enriched learning environment through the active participation of students in the educational process and through activities. Some of these activities include searching, collecting, selecting, editing, presenting information and exploiting the possibilities and choices offered by the new thematic module. It also seeks to cultivate communication and cooperative skills that upgrade the teaching practices and smooths the difficulties of both understanding and the communication of learning. Besides, with the help of the application form accompanying the teaching, the student is offered a research/interactive teaching tool, easy to use and entertaining while on the other hand the professor is given the chance to integrate the computer into the range of his teaching tools. This specific project aims to improve the learning outcome by facilitating the understanding that enhances interest, using modern computing technology according to the basic principles of pedagogical science.
Keywords: lesson plan, water conductivity, Bloom’s taxonomy, water, environmental education

A. Thysiadou, S. Christoforidis, P. Giannakoudakis

Curriculum Matters

Chemistry Students’ Difficulties in Learning Oxidation – Reduction Reactions

Резюме. The study explored students’ learning difficulties in oxidationreduction
reactions at the senior high school level; as part of a major research
project. The research approach for the project was a four-stage design-based research,using qualitative and quantitative methods. At the preliminary stage which is reported in this study, 213 third year students were sampled. All samples were selected through stratified and simple random sampling procedures. The students responded to a two-tier diagnostic test and interviews on conception of oxidationreduction reactions. In analysing the data, descriptive statistics and themes were used. The findings show that students had conceptual difficulties in the form of alternative conceptions and other difficulties such as conceptualising oxidising agents using the combined concept of oxidation and ionic charge. It was therefore recommended that Chemistry teachers should deploy the most appropriate pedagogical content knowledge that could help students conceptualise very well the concept of oxidation number and not to confuse it with ionic charges of particles involve in chemical equations.
Keywords: alternative conceptions; difficulties; models; oxidation; reduction;
reactions

K. Adu-Gyamfi, J.G. Ampiah

Teaching Efficiency

A Study of the Notions that Pedagogy Students Have on the Importance of Studying Seasonal Changes in the Formation of Basic Knowledge in Science Education in Grades 1 – 4 [In Bulgarian]

Резюме. This study determines the theoretical, methodical and professional readiness
of pedagogy students to use the teaching of seasonal changes in order to form the basics of natural science education in elementary schools. The knowledge, observation and analysis of the seasons are among the first ideas, related to natural science, that form in the mind of a child. In our latitudes, where four seasons turn, the impressions and sensory experiences are an important prerequisite for the formation of a complete and detailed
sensory base of children’s knowledge. The sensory basis is a key factor in developing important aspects of knowledge in the field of natural sciences (changes and development of natural objects, related to animate and inanimate nature, as well as cyclic recurrence of natural processes) when educating children in the subjects of The World Around and People and Nature. In this process, one of the preconditions for the formation of basic
knowledge in natural science is the inclusion of the cause-and-effect approach as a general cognitive scheme in the education.
Keywords: science education; seasonal changes in nature

V.A. Petrova, M.G. Delchev

Teaching Efficiency

Formation of Key Competences in the Classes of „Biology and Health Education“, 9th Grade, Through Using Interactive Methods [In Bulgarian]

Резюме. Biology as a Natural Science provides favorable opportunities for formation and development of key competences in students that will be useful throughout their life regardless of the professional field in which they occur. The objective of the study is to reveal the opportunities for application of the interactive methods and to examine their effectiveness in forming of key competences in “Biology and Health education” classes, IX grade. Methodological analysis of the educational content shows favorable opportunities for implementing the active approach as well as using the interactive methods of education in terms of the objective of the study. There has been presented fragments of the methodological construction of experimental lessons with interactive methods applied to form key competences. As a tool to establish the progress of the students are used the results of test assessment. Data from the survey of the student’s opinion is also presented in this article. Mathematical methods for processing the results are used and also graphical methods for their presentation. The conclusions made confirm the need for and the effectiveness of the experimental education in the field of studied issues.
Keywords: key competences, interactive methods of education, Biology and Health education IX grade, students

R. Davidova, K. Tomeva, M. Boycheva

Experiments

Amperometric Nitric Oxide Sensor Based on MWCNT Chromium(III) Oxide Nanocomposite

Резюме. Multiwalled carbon nanotube and Chromium (III) oxide nanocomposite
was used as a mediator in glassy carbon electrodes to improve the performance of electrode for the detection of nitric oxide in comparison with unmodified electrodes. The sensor could be operated as a detector in a flow injection analytical setup under physiological conditions (pH 7.5, 0.1 M phosphate buffer) with an operating potential from 800 mV (vs. Ag/AgCl), a flow rate of the carrier of 0.4 mL/min and an injection volume of 200 μL. The amperometric response of the sensor showed good linearity up to 200 μM with a sensitivity of about 21.6 nA/μM. The relative standard deviation for the repeatability of measurements for 100 μM NO was 3.9% (n = 10 measurements) and the reproducibility was 12% (n = 5 sensors). The effect of all investigated interferences (nitrite, ascorbic acid, dopamine and
L-arginine) was not fatal and at 800 mV the signal ratio of NO/NO2 – is around 10. The new sensor was successfully applied to the determination of NO in mice liver homogenisate after addition of L-arginine.
Keywords: nitric oxide; electrochemical sensor; nanocomposite; MWCNT;
chromium(III) oxide

A. Maloku, E. Queriqi, L.S. Berisha, I. Mazreku, T. Arbneshi, K. Kalcher

Experiments

Corrosion Behavior of Aluminium Alloys EN AW-6026 and EN AW-6082 [In Bulgarian}

Резюме. This article presents the results of study on the corrosion behaviour of aluminium alloys EN AW-6026 and EN AW-6082 in solution of sodium chloride (NaCl) at different pH of the medium. The corrosion resistance of thus alloys defined by gravimetric method. The results showed that the pH and concentration chloride ions can influence the corrosion rate of this alloys.
Keywords: EN AW-6026; EN AW-6082; aluminium alloys; corrosion behavior

K. Kamarska

From the Research Laboratories

The Effect of Aging Time on Mg/Al Hydrotalcites Structures

Резюме. In this study, the Mg/Al hydrotalcites-like compounds with Mg/Al
molar ratio of 2 was synthesized by coprecipitation method at pH ± 10.0, temperature 70°C for 1 hour. After cooling, it treated under aging treatment conditions at 30°C. The effect of various aging time on treated samples was studied for 1, 2, 3 and 4 days were chosen. The materials were characterized by powdered sample X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The XRD pattern obtained was typical of a hydrotalcite, where show the narrow and sharp symmetric (003) reflection and strong lines at low 2Ɵ angles. The spectra demonstration wide asymmetric peaks at higher angles, that are typical of clay crystals possessing a layered structure and are similar to the form of natural hydrotalcite. Furthermore, it is shown that aging at an increased time, better crystallinity and the treatment in water slightly than in the
mother liquid caused in a crystalline matter.
Keywords: Mg-Al hydrotalcites-like compounds; synthesized; aging treatment;
crystallinity; mother liquid

E. Heraldy, Triyono, S.J. Santosa, K. Wijaya, S. Shimazu

History and Philosophy of Science

The Periodic Table of Chemical Elements: Its History and Its Up-to-Date Status [In Bulgarian}

Резюме. The history and the up-to-date status of the periodic table of the chemical
elements are both examined. Only Mendeleev has been able to predict existence of new elements as well as to determine their chemical and physical characteristics. Later Antonius van den Broek and Henry Moseley have found that the chemical elements have been arranged in the Periodic Table according to their atomic number, not to their atomic mass as was the Mendeleev’s statement. The determination of the electronic configuration of the
atoms has shown that the periodical change of the properties of the elements is due to the periodical change of their electronic configuration. The role of the IUPAC in the updating of the Periodic Table has been commented, as well.
Keywords: D. I. Mendeleev; new elements; periodic table; IUPAC

I. Dukov

Свързани статии:

Сп. „Химия“, книжка 1/2019 Сп. „Химия“, книжка 3/2019 Сп. „Химия“, книжка 4/2019 Сп. „Химия“, книжка 5/2019