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This study describes the development and application of a three-tier test as a valid and reliable tool in diagnosing students’ misconceptions regarding some basic concepts about carbohydrates. The test was administrated to students of the Pharmacy Department at the University of Bijeljina (Serb Republic). The results denoted construct and content validity of the instrument and its high reliability. Considering the results entirely, it was determined that the presence of a third tier in a task significantly affected the number of identified misconceptions and the assessment of scientific knowledge. These findings suggest that certain incorrect responses should be attributed to the lack of knowledge rather than to misconceptions, and likewise, some correct responses should be attributed to the lucky guess rather than to scientific knowledge, which implies a higher credibility of the results obtained. In this study, several misconceptions about carbohydrates were revealed. As there are only a few studies examining students’ misconceptions in chemistry using three-tier tests available in literature, future research should focus on the further implementation of three-tier tests as a powerful tool for simple detection of misconceptions.

The aim of this study was the creation of a procedure for determining the cognitive complexity of stoichiometric tasks and its validation. The created procedure included an assessment of the difficulty of concepts and skills, and an assessment of the concepts' interactivity. There were 82 students who participated in the study, with an educational profile of a pharmaceutical technician. As a research instrument for assessing performance, test of knowledge was used. Each task in the test was followed by a seven-point Likert scale for the evaluation of invested mental effort. The validity of this instrument for the assessment of cognitive complexity was confirmed by a series of linear regression analysis where extremely high values of correlation coefficients are obtained among the examined variables: student's performance and invested mental effort (dependent variables) and cognitive complexity (independent variable).Key words: mental effort; performance; problem-solving; stoichiometry РАЗВОЈ НА ПОСТАПКА ЗА ПРОЦЕНА НА КОГНИТИВНА СЛОЖЕНОСТ НА СТЕХИОМЕТРИСКИТЕ ЗАДАЧИЦелта на ова испитување е создавање на постапка за определување на когнитивната сложеност на стехиометриските задачи и нејзина валидација. Разработената постапка вклучува процена на тежината на концептите и вештините и процена на интерактивност на концептите. Во испитувањето беа вклучени 82 студенти со образовен профил фармацевтски техничар. Како истражувачки инструмент за процена на перформансите беше употребен тест на знаење. Секоја задача во тестот беше следена на скалата на Likert од седум точки за евалуација на вложениот ментален труд. Валидноста на овој инструмент за процена на когнитивната сложеност беше потврдена со серија анализи со линеарна регресија со кои беа добиени многу високи вредности на коефициентот на корелација меѓу испитуваните променливи: перформансите на студентите и вложениот ментален труд (зависно променливи) и когнитивна сложеност (независно променлива).Клучни зборови: ментален труд; перформанси; решавање на проблеми; стехиометрија

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Many studies dedicated to the teaching and learning of organic chemistry courses have emphasized that high school students have shown significant difficulties in mastering the concepts of this discipline. Therefore, the aim of our study was to help students to overcome these difficulties by applying systemic synthesis questions, [SSynQs], as the instructional method in our intervention. This work shows that students from the group exposed to the new teaching method achieved higher scores on final testing than students from the control group, who were taught by the traditional method, when students' achievements in conventional, linear questions [LQs] and in [SSynQs] were studied. These results were followed by observation of lower levels of mental effort by students from the intervention group, and higher levels of mental effort in the control group, invested during solving both types of questions. This correlation between achievement and mental effort resulted in high instructional efficiency for the applied method in the intervention group, [SSynQs], and low instructional efficiency for the traditional teaching and learning method applied in the control group. A systemic triangular relation between achievement, mental effort, and instructional efficiency, established by each group and gender, emphasized that the application of [SSynQs] was more suited to female students than for male students because of [SSynQs] characteristics as teaching and learning tools and because of learning style and ability differences between genders.