Bette Davidowitz

Student-generated submicro diagrams: a useful tool for teaching and learning chemical equations and stoichiometry

This paper reports on a pedagogical approach to the teaching of chemical equations introduced to first year university students with little previous chemical knowledge. During the instruction period students had to interpret and construct diagrams of reactions at the submicro level, and relate them to chemical equations at the symbolic level with the aim of improving their conceptual understanding of chemical equations and stoichiometry. Students received instruction in symbol conventions, practice through graded tutorial tasks, and feedback on their efforts over the semester. Analysis of the student responses to formative test and summative exam items over consecutive years indicates that there was a consistent improvement in the abilities of the various cohorts to answer stoichiometry questions correctly. The responses provide evidence for diagrams of the submicro level being used as tools for reasoning in solving chemical problems, to recognise misconceptions of chemical formulae and to recognise the value of using various multiple representations of chemical reactions connecting the submicro and symbolic levels of representation. The student-generated submicro diagrams serve as a visualisation tool for teaching and learning abstract concepts in solving stoichiometric problems. We argue that the use of diagrams of the submicro level provides a more complete picture of the reaction, rather than a net summary of a chemical equation, leading to a deeper conceptual understanding.

Linking the Macroscopic and Sub-microscopic Levels: Diagrams

Explanations of chemical phenomena are nearly always focused at the sub-micro level, a level that cannot be observed, yet are normally provided with diagrams at the symbolic level. These diagrams represent the macro and sub-micro levels of matter. The connections between the macro level and the diagrams of the sub-micro level are not always apparent to students, indicating a need for chemical diagrams to be used carefully and explicitly. Having students draw and annotate chemical diagrams representing chemical phenomena at the sub-micro level can provide some insight into their understanding of chemistry at the macro level. Misinterpretation of diagrams can occur when the representations are not understood, when links are not made between the macro and sub-micro levels, or when the diagram is unfamiliar. Responding to these difficulties, strategies based on research and our experiences of teaching with diagrams are suggested for the choice and use of chemical diagrams depicting the sub-micro level in the teaching and learning of chemistry. These strategies provide opportunities for learners to construct acceptable personal mental models of the sub-micro level.

Quinolinone alkaloids from an Agathosma species

Abstract The aerial parts of a new species from the genus Agathosma yielded skimmianine and two new alkaloids which were identified by means of spectral data and synthesis as 4,6-dimethoxy-1-methyl-2(1H)-quinolinone and 2,6-dihydro-9-methoxy-2,2,6-trimethyl-5H-pyrano[3,2 c ]quinolin-5-one. Further related structures were synthesized and a 2D NMR study on the eight synthetic structures enabled us to correct some of the data appearing in the literature.

Students’ learning-approach profiles in relation to their university experience and success

What is the connection between student success and their approaches to learning? Do learning approaches develop with university experience? We explored these questions by constructing profiles using a specially developed fixed response instrument and administering this to students at two similar South African universities. Groups consisted of access course applicants, access course students, and first and second year mainstream chemistry students. Successful senior students showed more sophisticated approaches to learning than other groups. Unsuccessful students fell into two different categories: those using a surface approach, and predominantly first generation tertiary students who used deep approaches. We discuss possible reasons for the latter groups lack of success. These findings raise questions for academic development practitioners advocating the use of deep approaches. The instrument was found to be useful for both diagnostic and pedagogic purposes.

What lies at the heart of good undergraduate teaching? A case study in organic chemistry

Teaching organic chemistry at the undergraduate level has long been regarded as challenging and students are often alienated by the mass of detail which seems to characterise the subject. In this paper we investigate the practice of an accomplished lecturer by trying to capture and portray his pedagogical content knowledge, PCK, in order to reveal his tacit knowledge as a resource for others. Data analysed from interviews and a set of five introductory lectures showed the framing of Big Ideas designed to underpin later work in the course. Five manifestations of his practice emerged strongly from the data analysis, namely Explanations, Representations, Interaction with Students, Curricular Saliency and Topic Specific Strategies. This realisation allowed us to make inferences about his underlying knowledge and beliefs regarding how the discipline should be taught. We found that the most important aspect of his practice was his recognition of the basic underlying concepts to be mastered before starting the main part of the course, and his strong beliefs related to the learning of the discipline. The extraction and portrayal of these practices are a valuable resource for novice lecturers.

Assessment of preparedness of first-year chemistry students: development and application of an instrument for diagnostic and placement purposes

Abstract Many universities in South Africa use alternative admissions tests together with results of the Grade 12 examinations for access or placement. These tests focus on academic literacy and mathematical skills and do not provide information about proficiencies in disciplines other than mathematics. The implementation of a new curriculum for Grades 10–12 in South Africa generates a need to monitor preparedness of first-year students to align first-year curricula as closely as possible to the content of the new syllabi. The need for a tailor-made instrument to assess preparedness for chemistry at the tertiary level was prompted by the lack of suitable tests with the appropriate focus, depth and coverage for application in the South African context. This paper describes the development and evaluation of a test instrument designed to assess and monitor baseline conceptual understanding in chemistry at the secondary-tertiary interface. The study was carried out with mainstream students at the universities of Pretoria and Cape Town (N = 513 and 258, respectively). Data analysed using the Rasch statistical method confirmed that the majority of students from both cohorts was reasonably well prepared for chemistry at the tertiary level. The use of the instrument for diagnostic purposes was demonstrated. It was possible to identify gaps in the assumed pre-knowledge of students who have qualified for admission to chemistry at a tertiary level at their respective institutions. Inadequate pre-knowledge was most noticeable in the areas of chemical reactions and electrochemistry. In addition, the instrument also shows promise as a placement tool within programmes at a particular institution, i.e. in either mainstream or academic development programmes. Its predictive ability compares well with non-South African placement tests and with Grade 12 mathematics performance, the latter is widely used for this purpose in South Africa.

Development and application of a rubric for analysis of novice students’ laboratory flow diagrams

The purpose of this study was to develop and apply a scheme for the analysis of flow diagrams. The flow diagrams in question are a schematic representation of written instructions that require students to process the text of their practical manual. It was hoped that an analysis of the flow diagrams would provide insight into students’ understanding of the manual. To this end, we describe the development of a rubric for the analysis of flow diagrams. The analysis showed that most students were able to draw flow diagrams that showed evidence of deep processing, many of which could be used in place of the practical manual. Most students had some concept of how the apparatus worked, providing evidence of their initiation into the social practice of laboratory work. The analysis also showed that flow diagrams could be used to gauge the students’ level of understanding of the practical manual. Flow diagrams could be considered to be learning tools as well as part of the assessment for a practical session.

Preparedness for tertiary chemistry: multiple applications of the chemistry competence test for diagnostic and prediction purposes

The development of the Chemistry Competence Test was prompted by the extensive curriculum changes in the South African school system after democracy was established in 1994. As chemists, we were concerned that there might be a lack of articulation between secondary and tertiary levels, since we anticipated that curriculum changes would have an impact on the knowledge base and skills development of prospective students. A diagnostic test developed initially to document proficiencies of first-time entering students to South African universities has proved to be a versatile instrument for multiple uses. Apart from monitoring levels of preparedness for tertiary chemistry during a period of systemic change, it has also been used to evaluate institutional placement policies, to identify specific conceptual problems and procedural deficiencies, and to measure conceptual gains over the course of the first year at university. In addition, its application for the prediction of risk of failure in first-year chemistry based on cognitive and non-cognitive variables was demonstrated. All these findings are valuable resources to inform lecturers who are concerned about minimizing the conceptual gap between secondary and tertiary chemistry.

Two Dimensional NMR Study of 8-Methoxyflindersine, Skimmianine and Monocrotaline

Abstract Two dimensional HETCOR and long range HETCOR experiments were performed on a series of natural alkaloids which allowed complete 1H and 13C spectral assignments to be made. Protonproton and proton-carbon coupling constants are also given. Several errors in the literature are corrected.

Use of the Rasch measurement model to explore the relationship between content knowledge and topic-specific pedagogical content knowledge for organic chemistry

ABSTRACT Research has shown that a high level of content knowledge (CK) is necessary but not sufficient to develop the special knowledge base of expert teachers known as pedagogical content knowledge (PCK). This study contributes towards research to quantify the relationship between CK and PCK in science. In order to determine the proportion of the variance in PCK accounted for by the variance in CK, instruments are required which are valid and reliable as well as being unidimensional to measure person abilities for CK and PCK. An instrument consisting of two paper-and-pencil tests was designed to assess Grade 12 teachers CK and PCK in organic chemistry. We used the Rasch measurement model to convert raw score data into interval measures and to provide empirical evidence for the validity, reliability and unidimensionality of the tests. The correlation between CK and PCK was estimated as r = .66 (p < .001). We found evidence to suggest that while topic-specific PCK (TSPCK) develops with increasing teaching experience, high levels of CK can be acquired with limited teaching experience. These findings support the hypothesis that CK is a requirement for the development of TSPCK; proficiency in CK is, however, not necessarily associated with high levels of TSPCK.