Despite the importance of scientific inquiry in science education, researchers and educators disagree considerably regarding what features define this instructional approach. While a large body of literature addresses theoretical considerations, numerous empirical studies investigate scientific inquiry on quite different levels of detail and also on different theoretical grounds. Here, only little systematic research has analysed the different conceptualisations and usages of the overarching construct of scientific inquiry in detail. To close this gap, a review of the research literature on scientific inquiry was conducted based on a widespread approach to defining scientific inquiry as activities that students engage in. The main goal is to provide a systematic overview about the range and spectrum of definitions and operationalisations used with regard to single activities of the inquiry process in empirical studies. The findings from the review first and foremost illustrate the variability in the ways these activities have been operationalised and implemented. For each activity, studies differ significantly not only with respect to the focus, explicitness and comprehensiveness of their operationalisations but also with regard to the consistency of their implementation in the form of instructional or interventional components in the study and/or in the focus of the assessment of student performance. This has significant implications regarding the validity and comparability of results obtained in different studies, e.g. in the context of discussions concerning the effectiveness of inquiry-based instruction. In addition, the interrelation between scientific inquiry, scientific knowledge and the nature of science seems to be underexplored. The conclusions make the case for further theoretical work as well as empirical research.

The fluent use of the chemical language is a major tool for successfully passing chemistry courses at school or university as well as for working as a chemist, since chemical formulae are both a descriptive and a heuristic tool. However, numerous studies have revealed remarkable difficulties of students with chemical formulae both at school and at university. Although analysed for decades, current studies and practical experiences indicate that the misinterpretation of symbolic representations by students is still an ongoing problem. This review intends not only to summarize but also to categorize students' problems and difficulties when dealing with chemical formulae as reported in empirical studies. For this purpose, two categories of descriptive character were deduced from the empirical data: the type of chemical formulae and the operational activities that were required in the tasks of the studies. All in all, 38 articles were analysed on the basis of these categories. Students' problems and difficulties are then reflected based on three main problem areas: language-based problems, problems due to conceptual understanding, and problems due to inadequate selection and interpretation of formulae. These three areas call for a broader perspective in the interpretation of students' problems and thus lead to a discussion of implications for further research and changes in teaching practice.

Current reforms in the education policy of various countries are intended to produce a paradigm shift in the educational system towards an outcome orientation. After implementing educational standards as normative objectives, the development of test procedures that adequately reflect these targets and standards is a central problem. This paper constructs the theoretical framework for the assessment of students' content knowledge in chemistry. The resulting scheme and manual were used to develop model-based tasks in various content areas. Students' performances in paper and pencil tests taken in school grades 6 to 12 were analyzed. The quantitative data were used for a reliable classification of the tasks. The results shed light on the development of content knowledge in chemistry as well as on the various systematic factors that influence students' performance.