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An alternative analytical method for measuring the kinetic parameters of the enzymes invertase and lactase is described. Invertase hydrolyzes sucrose to glucose and fructose and lactase hydrolyzes lactose to glucose and galactose. In most enzyme kinetics studies, photometric methods or test strips are used to quantify the derivates of the substrates. The use of a commercial blood glucose meter to determine the hydrolyzed glucose is described. This inexpensive and efficient method can be used when teaching enzymatic kinetics in lower-level biochemistry laboratories.

In a series of three experimental studies, the effectiveness of three-dimensional computer simulations to aid the understanding of chemical structures and their properties was investigated. Arguments for the usefulness of three-dimensional simulations were derived from Mayer's generative theory of multimedia learning. Simulations might lead to a decrease in cognitive load and thus support active learning. In our studies, the learning effectiveness of three-dimensional simulations was compared to two-dimensional illustrations by use of different versions of a computer programme concerning the modifications of carbon. The first and third study with freshman students of chemistry and biochemistry show that no more knowledge was acquired when participants learnt with threedimensional simulations than with two-dimensional figures. In the second study with 16-year old secondary school students, use of simulations facilitated the acquisition of conceptual knowledge. It was concluded that three-dimensional simulations are more effective for younger students who lack the experience of learning with different visual representation formats in chemistry. In all three studies, a significant relationship between spatial ability and conceptual knowledge about the modifications of carbon was detected.

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Zusammenfassung: Dasc hemische Gleichgewichti st einw ichtiger undz ugleichs chwieriger Themenbereich fürL ernendew ie Lehrende.E inek ategoriengestützte Übersicht vonL ernendenvorstellungen kann einerseits alsPlanungshilfe verwendetwerden, um an denV orstellungenanzuknüpfen undsie gezieltals Lernmittel einzusetzen.A ndererseitsk anne rF orschenden dazu dienen,F orschungsbedarfez ui dentifizieren. Ergänzendi st es mçglichdie Ergebnisse einessolchen systematischen Überblicksals Ausgangspunktfürdie fachdidaktische Lehreund died amit verbundenenP rofessionalisierungsprozesse vona ngehendenLehrkräften zu nutzen.Der vorliegendeBeitrag hatdaher dasZiel, einensystematischen Überblick überdokumentierteLernendenvorstellungen zumT hemenbereichd es chemischen Gleichgewichts zu geben. Hierfürw urden systematisch aus2 84 Studien18Studien ausgewähltund untersucht,die explizit Lernendenvorstellungen zumchemischenGleichgewichtf ormulieren.D ie erfassten2 39 Vorstellungenw urdeni ns Deutsche übersetzt unda nschließend denf olgenden fünf fachbezogenenK ategorienzugeordnet: (1)Z eitraumder Einstellungd es dynamischenGleichgewichts,(2) Charakteristikad es chemischen Gleichgewichts,(3) ¾nderungd er Reaktionsbedingungen, (4)B eeinflussungd es chemischen Gleichgewichts durchZ ugabe einesK atalysatorsu nd/oderi nerten Gasesu nd (5) Heterogene Gleichgewichtssysteme. Abschließend werden Implikationenf ürd ie fachdidaktische Forschung undLehre skizziert.

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Teaching and learning chemistry or science, in general, could be described as building upon learners' existing conceptions. In order to support individual conceptual development, teachers should create opportunities for students to become aware of their thoughts. As this is very demanding in chemistry classroom practice with twenty-five or more individuals, pedagogical approaches and instructional support are needed. We argue for a collaborative learning practice that focuses on sharing and discussing individual conceptions on a chemistry-based phenomenon to build up a joint conceptual understanding. We state seven essential features for integrating this collaborative pedagogy successfully in classroom practice: (1) Becoming aware of one's own conceptions; (2) externalizing individual ideas; (3) initiating comparable situation models; (4) ensuring active involvement of all; (5) offering each learner opportunities to reflect on each other's conceptual understanding; (6) integrating decision-making processes; (7) offering the teacher measures to monitor the learning process. This paper is structured in three parts. Part I gives theoretical evidence to these essential features. Part II introduces the peer-interaction-method (PIM) as one of the possible collaborative learning approaches. The PIM is a pre-structured two-step collaborative learning method with instructional measures to meet the seven features. Part III reports a study with 136 students (grade 8 and 9), learning with the PIM in the context of combustion. The results give evidence to the features as being promising to foster individuals’ conceptual development in science learning. The paper concludes with a discussion, limitations and an outlook for further studies and pedagogies in the context of developing conceptual understanding in collaborative settings.