JOURNRL OF
Chemical Education: Software The Periodic Table Videodisc: Second Edition Alton J. Banks North Carolina State University Raleigh, NC 27695-8204 The Periodic Table Videodisc, a database of visual information ahout t h e chemical elements, was published in January 1989 (1). I t is a single-sided, 12-in., CAV-type video laserdisc that includes: a picture of each element; motion video sequences that show reactions (if any) of each element with air, water, acids, and base; and still pictures that show common and not-so-common uses and applications of each element. For a description of the content of the first edition of the Periodic Table Videodisc, see the abstract that appeared in January 1989 (2).The format of the original disc has not been changed, but a number of items have been revised or added. The part of the disc that shows reaction of lithium with air has been completely revised. This reaction is now done in the same way a s the reactions of sodium and potassium were done in the first edition. Acylindircal piece of lithium is cut with a knife to expose a clean surface (Fig. 1) and allowed to react withoxygen and nitrogen from the air. The surface tarnishes rapidly, hut not nearly as rapidly a s for sodium or potassium, which requires a dissolve i n the video sequence. The time elapsed i s indicated on the screen, and the beginning and end of the sequence are a t exactly the same frame numbers on the videodisc as the original Li + air reaction
Figure 2. Asample of beryllium is displayed in a sealed glass vial
strong lighting required for video, the sample warms above 28.5 "C and melts as i t reacts with air (Fig. 3). This special issue of JCE: Software is part of an effort to provide alternative approaches that enhance teaching of descriptive chemistry. The Periodic Table 15deodisc was conceived as a database of visual information about applications, properties, and chemical reactivity of the elements. It provides a broad range of reactions, all carried out in the same (or nearly the same) way so that comparisons are easily made by students. It is also designed with and without labels identifVina . . each element, so that the video material can be used ili part of a quiz or(~ximinntinn. Thc video laserdisc m d i u m obviates concerns that normally accompany presentation of descriptive chemistry: safety, costs of materials, disposal of reaction products, time for preparation and clean up, and visibility of the presentation to all members of the class. In cases where an element or reaction can be shown safely using materials normally a t hand, the videodisc provides a supplement that can show details that would be missed by students sitting far from the demonstration bench. It also provides a n excellent means of reviewina reactions and oro~erties a t a later time. A
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Figure 1. A sample of lithium has just been cut to expose a clean surface to the atmosphere.
The picture of beryllium has been changed to a sample that is more readily seen than i n the original disc (Fig. 2). Pictures of niobium and uranium have also been added. This brings the number of elements for which there is a picture to 67. Through the cooperation of the American Chemical Society we have been able to obtain video of rubidium and cesium reacting with air and with water. The demonstrators in this case are Jim and Julie Ealy. Cesium is especially interesting because of its low melting point. Under the
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Journal of Chemical Education
Figure 3. A sample of cesium slowly melting. (The clear liquid is oil under which the cesium was stored.)
