The main problem in students' lower achievement lies in the cognitive complexity of the problem. The aim of this research was to create and validate the procedure for the assessment of the cognitive complexity of chemical technology problem tasks. The procedure included the creation of Tables for assessing the difficulty of concepts in chemical technology problems and their interactivity, assessment of the numerical rating of cognitive complexity of the analyzed tasks, and conducting of research. Research included 50 students. Data were collected with the test of knowledge which was used for the assessment of students´ achievements and invested mental effort. The validity of this procedure was confirmed by a series of correlation analyses where statistically significant values of correlation coefficients were obtained among the examined variables: students’ achievements, invested mental effort and cognitive complexity. The largest contribution of this procedure is that it is designed to show an objective value of the cognitive complexity of tasks in the domain of chemical technology. Good estimation of the numerical values of cognitive complexity can help teachers to better predict students' achievement, and at the same time to take care to avoid cognitive load. Keywords: cognitive complexity, problem-solving, chemical technology.

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This paper proposes a novel application of knowledge space theory for identifying discrepancies between the knowledge structure that experts expect students to have and the real knowledge structure that students demonstrate on tests. The proposed approach combines two methods of constructing knowledge spaces. The expected knowledge space is constructed by analysing the problem-solving process, while the real knowledge space is identified by applying a data-analytic method. These two knowledge spaces are compared for graph difference and the discrepancies between the two are analysed. In this paper, the proposed approach is applied to the domain of stoichiometry. Although there was a decent agreement between expected and real knowledge spaces, a number of relations that were not present in the expected one appeared in the real knowledge space. The obtained results led to a general conclusion for teaching stoichiometry and pointed to some potential improvements in the existing methods for evaluating cognitive complexity.

This research considered students' abilities to read images about dispersed systems, taken from the chemistry textbook. 103 high school students (37 males, 63 females, and 3 unknown) from the school "Svetozar Marković" in Novi Sad, Republic of Serbia, were included as the research participants. Students' abilities to suggest the titles of the realistic, conventional, and hybrid textbook images about dispersed systems, as well as their written interpretations of images contents, were examined. The collected data were analysed qualitatively, and information about students' conceptual understandings and misunderstandings about selected chemistry topic was provided. Identified misunderstandings, some of which are the contribution of this research, gave significant results. Additionally, it was concluded that the majority of students' difficulties were related to reading realistic textbook images. Students relied on what they literally saw in the photography without making proper connections with chemical contents about dispersed systems. The findings of the present research could be helpful for science teachers and educators, interested in how and why students use textbook images to learn science concepts. They will also alert authors and textbook illustrators to pay more attention to the selection of appropriate textbook images.

This communication describes the actions undertaken to translate the chemical crystallography course at the University of Novi Sad, Serbia, from face-to-face to online instruction, as well as the emerging challenges encountered during this unprecedented time. As part of the global efforts to respond to the recent disruptions to teaching, our purpose in this paper was to provide insights about useful methods that can be used in chemical crystallography courses to alleviate the concerns resulting from this shift in modality and to point out to some aspects of teaching that did not work as expected, despite the optimum efforts.