This paper is a reflection on a three-year longitudinal study that explored the development of children's concept of a substance, for which detailed results concerning children's understandings have been reported elsewhere. The attention in this paper is on the methodological features related to the longitudinal nature of the study and the…

This design study tracks the development of student thinking about natural variation as late elementary grade students learned about distribution in the context of modeling plant growth at the population level. The data-modeling approach assisted children in coordinating their understanding of particular cases with an evolving notion of data as an…

To demonstrate how Newton's first law of motion applies to students' everyday lives, the author developed a learning cycle series of activities on inertia. The discrepant event at the heart of these activities is sure to elicit wide-eyed stares and puzzled looks from students, but also promote critical thinking and help bring an abstract concept…

The persistence of students' misconceptions about motion illustrates the enormous difficulty that teachers face in their attempts to overcome these with traditional physics instruction. An understanding of students' ideas about motion and ways to incorporate them into successful instructional approaches can be obtained from an analysis of…

In this article we present the fascinating reconstruction of an accident where a car hit a boy riding his bicycle. The boy dramatically flew several metres through the air after the collision and was injured, but made a swift and complete recovery from the accident with no long-term after-effects. Students are challenged to determine the speed of…

Lessons about elementary particles at the secondary school level can degenerate into listing a zoo of particles and reactions, resulting in disorganized and rather meaningless knowledge. A more powerful way is to focus on conservation laws, symmetries and reaction diagrams. The conservation laws and symmetries provide generalizing power that…

A simple circuit problem treating an inductor, resistor and battery in series has uncovered a basic misconception of first-year students. The misconception is not about circuits or electrical properties but concerns rather the meaning and interpretation of the rate of change (instantaneous slope or derivative) of physical quantities. Resolving the…

The study of astronomy, as an important part of any science education programme, provides our students with insights into more than just the cosmos. It may also serve as a mechanism to link them to other natural and social sciences. This article examines equally valid interpretations of the constellation Canes Venatici as an example of how the…

Cladistics is one of the most commonly used methods for reconstructing evolutionary ancestries. Developed by Willi Hennig in 1966, cladistics use patterns of shared derived characters called synapomorphies to infer the order of lineage divergences within a group of organisms. Unfortunately, while this methodology forms the foundation of many…

The use of biocatalysis and biotransformations are important tools in green chemistry. The enantioselective reduction of a ketone by crude plant parts, using carrot ("Daucus carota") as the reducing agent is presented. The experiment introduces an example of a green chemistry procedure that can be tailored to fit in a regular laboratory session.…

Metal rods of high purity for many elements are now commercially available and may be used to construct a display of relative densities. We have constructed a display with nine metal rods (Mg, Al, Ti, V, Fe, Cu, Ag, Pb, and W) of equal mass whose densities vary from 1.74 to 19.3 g cm[superscript -3]. The relative densities of the metals may be…

This article describes the central limit theorem (CLT) and its relation to analytical chemistry. The pedagogic rational, which argues for teaching the CLT in the analytical chemistry classroom, is discussed. Some analytical chemistry concepts that could be improved through an understanding of the CLT are also described. (Contains 2 figures.)

For 137 years Markovnikov's rule has been extensively used in organic chemical education and research to describe the regioselectivity in electrophilic addition reactions to alkenes and alkynes. When the structures of the final reaction products are used as reference, the rule requests that certain polar addition reactions be termed…

Information in the nervous system is conveyed by impulses called action potentials: large, transient electrochemical changes in a neuron's membrane. Though action potentials are a basic feature of neurons, teachers often have trouble explaining this neurophysiological concept, and students have difficulty understanding it. While easy-to-understand…

Some potential contributions of invariants, heuristics, and exemplars to the perception of dynamic properties in the colliding balls task were explored. On each trial, an observer is asked to determine the heavier of 2 colliding balls. The invariant approach assumes that people can learn to detect complex visual patterns that reliably specify…