Liquefaction of Carbon Dioxide Shifting an Equilibrium: Adding or Removing a Substance Shifting an Equilibrium: Changing Volume Relative Reactivity: Strong Acid, Weak Acid, Buffer Solution
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Orange Tornado: Precipitation of Mercury(//) Iodide Paramagnetism (Nitrogen and Oxygen) Paramagnetism (Compounds) Reactions of Metals + Iodine
Ozone: Absorbance of UV Light
Hydrochloric acd, acetic acid. and an acetlc acla-acetate ouner (leftto right) are added simultaneously to sarnpies of sodium hydrogen carbonate to illustrate relative rates of reaction.
About This Issue John W. Moore and Jon L. Holmes University of Wisconsin-Madison Madison, WI 53706-1396 How to Use This Videodisc "ChemDemos" has been designed to address problems many teachers face in providing their students with views of important chemical reactions: safety, availability of substances and apparatus, and disposal of toxic or hazardous substances. The demonstrations on this disc have been selected because one or more of these problems is likely to prevent a teacher from doing the demo live. Thus the disc provides a n important resource for first-year chemistry courses. Every demo on the disc illustrates a t least one principle that is a n important component of such a course and that might not otherwise be demonstrated. "ChemDemos" can be used stand alone with only a videodisc player and hand control or barcode reader for classroom presentations. If a laserdisc player with a serial connection for a computer is available, demos can be shown even more easily under computer control. Software is provided for both IBM PSI2 or PC computers with Windows a n d for Macintosh computers with Hypercard. Whether the disc is used stand alone or with a computer, students will see close-up views of each reaction, and a teacher can direct their attention to important obsewations a s well as provide interpretations of what is seen. The laser videodisc medium allows for immediate access to 780
Journal of Chemical Education
each demo, pausing, backing up, viewing in slow motion, repeating, and carefully examining what is happening. The documentation provides information about each demonstration including topics for which the demo is suitable. For example, the water-gas reaction shows how water can react with hot charcoal to form a combustible gas (demonstrated by having the gas ignite). This fits beautifully into a discussion of energy resources and the importance of having those resources in easily usable forms (gaseous versus solid fuel, for example). "ChemDemos" can also be used by students individually or in small groups. Using the printed documenation teacher can prepare written materials that direct students to view appropriate demos, make observations, and draw conclusions. This can be done using frame numbers and a hand control or with barcodes. Barcodes in the documentation can be photocopied into locally produced materials for this purpose. The demos can also be built into computer-based materials developed by a n individual teacher. Such materials can be created using Hypercard on a Macintosh, ToolBook under Windows on a n IBM computer, or other such multimedia authoring systems. Such uses are allowed, even encouraged, provided they are noncommercial. HardwareISoftwareRequired "ChemDemos" is a 1 2 h , double-sided, 60-minute, CAVtype video laserdisc in NTSC format (it is incompatible with the PAL standard used in many European countries). It may be operated from any videodisc player usinga handheld remote-control keypad or a barcode reader. (Consult the supplier of your videodisc player to ascertain whether it can be used with a barcode reader.) To make the video presentation visible to students in a classroom either a large-screen color monitor or a color video projection unit will he needed. The size of the monitor (or the need for a projection unit) depends on the size of the class to which the presentation will be made. If the disc is to be used under comouter control the videodisc player must have a serial (RS-232) interface. Software is supplied with the videodisc for both Macintosh and IBM compatible computers. The Macintosh version reauires an Aoule Macintosh with a hard disk drive and ~ y p e f i ' a r dor ~ y p k f l a r dPlayer version 2.1 or later. Macintosh computers running under System SoRware version 6 without Multifinder must have a t least 1MB of memom Svstem SoRware version 6.0.5 or later. and H m r Card 2.0or iater. Macintoshes using System 7 or sys& 6 with Multifinder require a minimum of 2 MB of memorv. The ~ i n d o w s ! BPC ~ version requires Microsoft Wi~"~dows version 3.0 or later and associated hardware as defined by MimsoR. We recommend an IBM-PCIAT, PSI?,, or compatible computer with an 80386 or higher processor, a minimum of 4 MB of memory, a hard disk, one floppy disk drive to install the software. and a Windows-com~atibleeraohics card. t e r cornpat: such as a n IBM VGAOTa super V ~ ~ a i a ~&
