Liquid carboxylic acids (or primary amines) with limited solubility in water are dissolved by addition of aqueous sodium hydroxide (or hydrochloric acid) on the stage of an overhead projector using simple glassware and very small quantities of chemicals. This effective and colorful demonstration can be used to accompany discussions of the…

Intermolecular forces and surface tension gradients in solutions lead to remarkable flows, known as Marangoni flows, where liquid flows from a region of low surface tension towards higher surface tension. Details of these flows, not visible to the naked eye, are made visible on an overhead projector owing to variation in the index of refraction.…

The construction of a device is described which converts an ordinary horizontal-stage overhead projector into a vertical-stage projector. The parts cost $60 and seven hours of labor are required. (BB)

Describes the development of a three-dimensional projection system used to present structural principles by means of slides. Polarization of images from two planar projectors and viewing through polarized lenses gives stereo results. Techniques used in producing the slides and constructing the equipment are given. (TS)

Because class size often limits student opportunity to handle individual models, teachers use stereoscopic projections to demonstrate structural features. Describes three-dimensional pointers for use with different projection systems so teachers can indicate a particular atom or bond to entire classes, avoiding the perspective problems inherent in…

Describes a method using lap-dissolve slide techniques with two or more slide projectors focused on a single screen for presenting visual effects that show structural features in extended arrays of atoms, or ions involving up to several hundred atoms. Presents an outline of an introduction to the structures of crystalline solids. (CS)

Describes a lecture teaching technique called lap-dissolve projection in which two slide projectors are operated alternately so that one visual image fades away while the next appears on the same screen area. (MLH)

Discusses the use of lap-dissolve projection to give students pre-laboratory instruction on an upcoming experiment. In this technique, two slide projectors are operated alternately so that one visual image fades away while the next appears on the same screen area. (MLH)

Advantages and disadvantages of using multi-image or lap-dissolve (LD) slide techniques in large lecture sections are discussed. Production, use, and evaluation of LD programs are also discussed. Indicates that these programs are an effective way of improving instruction on visually oriented topics. (JN)

Discusses the use of a simple apparatus to measure contact angles between a liquid drop and a solid surface which are determining factors of wettability. Included are examples of applying this technique to various experimental situations. (CC)

The construction and uses of a device to facilitate the use of an overhead projector to show chemical reactions is presented. Materials and instructions for construction as well as reactor vessels are discussed. (CW)

Reports on a screen projectable model of atomic orbitals useful in developing a student's understanding of molecular structure. (SL)