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In teaching the science of the nano world, ball-and-stick molecular models are frequently used as 3D representations of molecules. Unlike a chemical formula, a molecular model allows us to visualise the 3D shape of the molecule and the relative positions of its atoms, the bonds between atoms and why a pair of mirror isomers with the same atoms, bonds and bond angles are two different molecules, etc. These models also show arrangement of atoms in allotropes and molecules forming crystal lattices in materials science. In this article, we describe how to construct molecular models using low-cost toy beads. The retail price of a pack of 36 beads is about 2 British pounds. Such a low cost makes it affordable for most schools to arrange small-group or individual model-building activities. (Contains 17 figures.)

In this article, we describe a simple method which can be used to measure the efficiency of a low power dc motor, a motor-converted dynamo and a coupled motor-dynamo module as a function of the speed of rotation. The result can also be used to verify Faraday's law of electromagnetic induction. (Contains 1 table and 8 figures.)

We describe a physics investigation project inspired by one of the adventures of Odysseus in Homer's "Odyssey." The investigation uses the laws of mechanics, vector algebra and a simple way to construct a fan-and-sail-cart for experimental verification.

This article illustrates how the overhead projector can be used as a light source in some peculiar ways for physics demonstrations. Five examples are included: (1) Study of chromatic aberration; (2) Making giant Newton's rings; (3) Comparison of the rate of heat absorption by different surfaces; (4) Demonstration of greenhouse effect; and (5) Production of an intense parallel light beam.

Reports on a study of alternative conceptions held by junior high-level secondary science teachers enrolled in an inservice teacher-training program. Finds that science teachers are inadequately prepared to teach a broad and balanced science curriculum. Contains 34 references. (Author/WRM)

We describe three independent methods for measuring the speed of radio waves along a homemade coaxial transmission line. These experiments confirm the predictions obtained from a general circuit equation subjected to simple boundary conditions. The sources of errors and relative merits of each method are discussed.

Discusses the commonly held misconceptions on heat and examines potential contributing factors. Defines and provides examples of internal energy and heat. Suggests approaches to the teaching of heat for secondary level students. (ML)

Reports the development of an instrument for gathering information about the attitudes of Hong Kong secondary school teachers towards evolution. Describes the establishment, through criteria found in the literature, of a logical and systematic procedure for the validation of this Likert-type instrument. Tentatively found that the 15-item scale was a reliable instrument. (KO)

An impressive, but once difficult experiment to build, has been modified and simplified to serve an interesting method of demonstrating static electricity. The traditional design of the Kelvin water-drop generator was not easy to construct, affected by humidity and was not reliable. The replacement components should be well-received by high school and college teachers.

Newton's rings are often used in the physics classroom to demonstrate interference patterns but are hard to see with the traditional apparatus. A modified apparatus generates large rings that are visible to the whole class using a Plexiglass sheet with one kilogram weights at the corners to bend the sheet into a slightly convex shape. Visible light's wavelength is clearly demonstrated while the shape of the rings can be modified by adjusting the weights.

Students learning about the Archimedes principle usually have problems in associating the cause of upthrust with the pressure difference between the upper surface and the lower surface of the submerged body. Two experiments illustrating the relationship between upthrust and pressure difference were designed. Since the experiments made use of a piston which could be made to float or sink by varying certain external conditions, the piston was termed a Cartesian diver.

In this note, we introduce a simple homemade toy called the brush-creeper, which can glide forward with no propellers, limbs, wheels, and seemingly no movement of any kind that can push forward against the ground. The toy arouses pupils' interest and their incentive to ask "Why?" in lessons related to friction.

The authors note how a balloon rocket is often used to demonstrate Isaac Newton's third law of motion and suggest a balloon helicopter may be a more efficient apparatus for this purpose. Taiwanese origin of the toy and repeated application of the third law are discussed.

Circuits are often used to demonstrate electrical resonance to science students, but students may not understand why certain values of inductance, capacitance or resistance have to be used. Light bulbs with very low voltage should be used to minimize the effect of resistance. Further complicating such experiments is the fact that most inductors and capacitors are not pure reactance.

Brownian motion is often demonstrated in junior-high level classes with a traditional experiment involving trapped smoke, but often the experiment is cut short due to time limitations and poor observations result. However, Brownian motion can be better observed through the use of a microvideo camera connected to the eyepiece of a microscope and projected onto a television monitor or screen for viewing.

A standard lab experiment to indicate greenhouse warming effects can be modified to produce significant results. The standard experiment uses two thermometers placed in sunlight with one thermometer placed in a transparent chamber. This experiment calls for inserting a piece of paper inside the chamber.

Describes an experiment for determining the refractive index. Discusses the experiment procedure and mathematical expression for calculating the index. Provides two geometrical diagrams and a graph for determining the index with a typical data. (YP)