Presents ways in which the valence bond (VB) theory describes the bonding and geometry of molecules, following directly from earlier principles laid down by Pauling and others. Two other theories (molecular orbital approach and valence shell electron pair repulsion) are discussed and compared to VB. (CS)

Described is a creative approach to the use of contact slides as a means of student participation in a learning unit on animal classification. The finished product is a slide presentation in which students themselves have made the slides and taped the narration. (CS)

Presents an analysis of a recently published science textbook for grades 1 to 6. An evaluation of the process and content of the student text and teachers guide are given. (SA)

Describes demonstrations used by the nineteenth century physicists to determine if two bodies oscillating at the same acoustic frequency were in phase. (GA)

Derives an explicit representation of the permutation operator in terms of coordinate and momentum operators. (Author/GA)

Presents a system of introducing students to the study of ecology, using a hierarchical organization of organisms into individuals, populations and communities; and using three phases of the environment--space, energy and matter. Discussed is the usefulness of a matrix system when relationships between ecological subheadings are explained. (CS)

Diagrams a quick, improvised cardboard circuitry for battery holder, bulb socket, and switches. Materials include corrugated cardboard, paper clips, and rubber bands. Assembly useful in determining the electrical conductivity of substances. (CS)

Describes the basic acoustical principles of percussion instruments whose vibrating members are multidimensional. (MLH)

Included in this introduction to the study of algae are drawings of commonly encountered freshwater algae, a summary of the importance of algae, descriptions of the seven major groups of algae, and techniques for collection and study of algae. (CS)

Describes the use of the "Science Citation Index" in deciding whether to keep older basic science books that have failed to meet other criteria for collection retention. It is concluded that manual searching of the indexes proved feasible and reliable, while the lack of book titles on the online version reduced reliability of weeding…

Discusses teaching the names, symbols, and charges of 53 common ions along with those of the elements. Provides an ion quiz sheet. (YP)

Describes some experiments showing both qualitatively and quantitatively that aerodynamic lift is a reaction force. Demonstrates reaction forces caused by the acceleration of an airstream and the deflection of an airstream. Provides pictures of demonstration apparatus and mathematical expressions. (YP)

Explains the lifting force based on Bernoulli's law and as a reaction force. Discusses the interrelation of both explanations. Considers accelerations in line with stream lines and perpendicular to stream lines. (YP)

Identified are errors in diagrams from the textbook "Physics" (Little, Brown, and Co., Boston, 1987). Presents and discusses the errors in eight textbook diagrams. The errors include mechanics, optics, and electricity. (YP)

The Moire pattern is the shimmering pattern which looks like an odd interference pattern in window screens or folds of nylon shower curtain. Illustrates some of the ways the effect may be used, including demonstration of wave interference, detection of small displacement, persistence of vision, contour measurement, beats, and optical clearness.…