This study presents our attempt to elicit students' progression in understanding the matter concept. Past work has identified the big ideas about matter students need to understand, the many everyday understandings students hold about these ideas, and levels of understanding through which students progress in developing understanding of the big ideas, or the matter concept as a whole. None of this research, however, has investigated whether the hypothesized big ideas represent distinct ideas and if so, how students' progression in developing understanding of the big ideas compares across them. With our study, we aim to provide a more comprehensive picture about students' progression in understanding matter by investigating students' progression in developing understanding of four big ideas about matter (structure and composition, physical properties and change, chemical reaction, and conservation). Based on a framework developed from a systematic review of the literature that identifies five levels of understanding for each of the four big ideas, an instrument based on Ordered-Multiple-Choice (OMC) items was developed to assess students' level of understanding about each idea. This instrument was administered to N ¼ 1,388 students from grades 6 to 13. Multi-dimensional Rasch analysis was used to analyze the data collected. Our analyses confirm that the four big ideas represent distinct ideas although our examination of students' progression in understanding these ideas suggests that three of them develop in parallel. A detailed comparison of students' progression suggests that the hypothesized levels mark a hierarchical series of levels through which all students progress in the same order although not necessarily at the same pace. Together with the instrument developed which provides an efficient and reliable way to assess students' understanding our work may help to inform future efforts in optimizing instruction about matter and investigating students' trajectories in developing an understanding of the matter concept. #

Helping students develop a sound understanding of scientific concepts can be a major challenge. Lately, learning progressions have received increasing attention as a means to support students in developing understanding of core scientific concepts. At the center of a learning progression is a sequence of developmental levels reflecting an idealized progression toward understanding a particular core concept. This sequence is supposed to serve as a basis for designing instruction that can foster learning as well as assessments that can monitor students’ progression. So-called ordered multiple-choice (OMC) items have recently been suggested as a simple and effective way of assessing students’ level of understanding of a core concept. This article details our efforts in developing an instrument for assessing students’ understanding of the structure and composition of matter based on OMC items. Ten OMC items were developed and administered to a sample of N = 294 students in grades 6–12. Rasch analysis was used to investigate instrument functioning and to determine linear measures of person abilities and item difficulties. In addition to the OMC items, students were administered corresponding open-ended items in order to investigate the validity of the results obtained through the OMC items. Our findings suggest assessing students’ understanding of scientific concepts through OMC items is indeed quite worthwhile and should be subject to further research.

This manuscript presents a systematic review of the research on how students conceptualise matter. Understanding the structure and properties of matter is an essential part of science literacy. Over the last decades the number of studies on students' conceptions of matter published in peer-reviewed journals has increased significantly. These studies investigated how students conceptualise matter, to what extent students are able to explain everyday phenomena or how students develop an understanding of matter over time. In order to understand how students progress in their understanding of matter, what they understand easily and where they have difficulties, there is a need to identify common patterns across the available studies. The first substantial review of research on students' conception was provided in the 1990s with the aim to organise students' understanding of matter into four categories: students' conceptions about (1) chemical reactions, (2) physical states and their changes, (3) atoms, molecules and particle systems and (4) conservation. The aim of this review and analysis is to identify how subsequent research on students' conceptions of matter adds to this framework. The last comprehensive review of research on students' understanding of matter was carried out in the early 2000s. Thus, we analysed studies on students' conceptions of matter published within the last decade in five peer-reviewed journals of science education. Our findings suggest that research has moved from categorising students' conceptions to analysing students' progression in understanding matter. Based on our findings, we also identified typical pathways by which students may develop over time related to the four categories identified in previous reviews. As a conclusion, we present a model describing students' progression in understanding matter which may contribute to the development of a K-12 learning progression of matter.

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Experimentierkästen sollen Schülerinnen und Schülern die Möglichkeit bieten, ohne fachkundige Aufsicht naturwissenschaftliche Fragestellungen zu bearbeiten. Die beiliegenden Experimentieranleitungen sollen sie dabei begleiten – im Idealfall ohne rezeptartig durch die Experimente zu leiten. Im Rahmen des im vorliegenden Beitrag vorgestellten Projekts haben Schülerinnen und Schüler der Oberstufe handelsübliche Experimentierkästen und Experimentieranleitungen daraufhin untersucht, inwieweit dieser Spagat gelingt.