Disk 5, which deals with percentage composition and empirical formulas, first demonstrates the potassium chlorate experiment. Although good directions are given for heating until the residual weight is constant, there are no ohvious changes in the material in the simulated crucible. Thus, the student must guess about how long to heat, since no specific directions are given. In the two examples that follow the first leads the student through the process, and the second provides an interactive format for the student to try the calculations. It seemed that there could have been more variety in the four practice problems that followed. The concepts of empirical and molecular formula are neat introduced. The use of automatic subscripting for numbers is an excellent feature of the few example prohlems that are given here. Simulation of the magnesium-hydrochloric acid experiment offers "real" data for calculating molecular formulas,and this is followed by five empirical formula problems which are nicely varied in their difficulty. This disk is one of the better features of the collection, because it relies least on "page turning" and takes advantage of the computer's capability to be interactive, as well as the rather nifty simulations. Chemaze, the sole program on Disk 6, is e general chemistry program based on PacMan. The player maneuvers aflask containing either HCI, HN03, NH3, or NaOH around a maze. The flask is hotly pursued by a beaker, which also contains one of the four reagents. At the eornerr uf the maze are "iilling statrons" where the player enn chanrt - thecmtenrsof rhr tlask. At arrnteair locations in the maze are nine other reagents which block the maze; they will disappear when encountered by the flask if it contains a solution that will react with the substance. The goal is to remove all nine reagents without being caught by the beaker. If the beaker catches the player's flask and a reaction can occur, it will, and the game is over. Points are deducted for attempting to react the material in the flask with a reagent that does not react or if the beaker catches the flask when no reaction will occur.T h e game provides an entertaining way t o learn that nitric acid, not hydrochloric acid, reacts with copper or that ammonia will react with silver bromide. However, as with many educational video games, t h e education is quickly supplanted by gamesmanship, by trying to score the largest score without reference to the chemistry. In one ease, for example, a student who had learned all the reactions and achieved several perfect scores in one session, had t o relearn all of the reactions in a second session. Nevertheless, the game provides amusement and may intrigue un k h e r w s e unmotivatwl student. I'he ldral tiarei, Bt,ylp's 1.aw and Charle.;'Launre nreitntedim the tinoldiskThe authors ret& to the drill and practiceproblem-solving routine far this material, and on the whole it is handled reasonably well. There are four practice problems each for the Boyle's Law and Charles' Law sections, and they are nicely graded in difficulty. Included is a good demonstration of the origin of the absolute zero scale. Errors, although rare, occurred more freouentlv on this disk than anv ,of the others. " I { ~ p l u t t ~was I " misspelled. and there were wme inconristencies ahour requiring unitx.
Summary. One colleague has commented that this set of general chemistry programs is"important," and indeed i t is. Smith, Chabay, and Kean have assembled a set of programs that, in spite of their flaws, may be the most useful CAI for general chemistry. The programs are easy to use, either as a whole package or as individual disks, and they provide a variety of drills which will save time for busy instructors. The material that is covered wauld be best for students just beginning chemisty, although certain parts might well benefit students in astrong college chemistry course. The programs can be used as an autotutorial, too. There are two principal weaknesses of the programs. First, the levels of skill required of thestudent are wide, perhaps because the authors were too ambitious in what they set out t o do. As a result, students can lose interest quickly if parts of the program seem too easy or trivial, when there are challenging and useful exercises elsewhere. Second, the programs are not easily modified. Instructors cannot easily add their own prohlems, for example,or change existingones to suit their particular situation. Overall, these programs will he very useful insomecontexts, less soinothers. Potential purchasers should be certain that the ao~licationsthe" envision for these materi&will be benefi'cialto their students before investing in the programs.
Robin B. Kinnel Hamilton College Clinton. NY 13323
introductionto Crystallography David Y. Curtin. COMPress. A Division of Wadsworth, Inc., P.O. Box 102. Wentworth. NH 03282
Hardware: Apple I1 family, one or two disk drives Software: DOS 3.3 Components: Two disks and backups Level and Subject: Junior level or above; crystallography cost: $120 Review I
mentation was provided. I t is "protected" software, although since no effort was made t o crack the protection scheme, no report canbe made here on mattersof interest such as copying and backup. The price is $120. The package is self-hooting, and like many programs of its genre, bypass Apple's unsatisfactory tent screen in favor of manipulation and text presentation directly on the graphics screens. Since i t takes over control of the machine, i t provides a rather restrictive user environment. For example, although some mention is made of printers in the introduction, no provision is apparently made for hard copy of any sort. Otherwise, no problems were experienced with the mechanics of using these programs. The program delivers 19 "lessons" on 3 major topics: Crystal Geometry (2 lessons), Crystallographic Symmetry (13 lessons), and Space Groups (4 lessons). Lesson material is a mix of terse exposition and very simple problems, and each of the lessons delivers a few screens of text in this general format. Each problem has provision for assistance, and in many cases this "help" function is absolutely essential. For example, it is clearly impossible to answer questions about the values of angles seen in a two-dimensional projection of a three-dimensional figure when one has no idea haw the oroieetion was constructed. Initial aecrsJ 11, the "hrlp" functron for n particular problem p v e 9 R hint, u h k the s ~ r o n daccess gives the answer directly. A number of students looked a t this software. They ranged from freshman with no exposure t o crystal structure concepts, to juniors taking physical chemistry laboratory, to graduate students who were very knowledgeable regarding solid state and structural chemistry. The reaction was ultimately one of same indifference, although several students were very excited a t first by the impression that this wauld be a n entertaining way to review important material. Despite the fact that only about 30-45 min is required to go through the entire set of lessons, most students couldn't he bothered to complete more than one or two of them. The graphics presentation is limited by the hardware and is poor, as one would expect from the available screen resolution. The text has no particularly redeeming graces. In fact the wording is very carelessly chosen in man" ulaees. For examole. the remark is made that a meiold rutatlon a x , * rutates ~d>jrrts :l60 deprws, so that a properd:itincturn h ~ r u r r nsymmetry, Iernenrs nnd sytnmetry operations is not made. This reviewer wauld not allow use of the package by students without considerable editing .of phraseology. In a few places, minor exten-
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This software package is designed to provide an "introduction to those concepts required t o grasp t h e chemical significance of published crystalstructures."It contains no discussion of the actual process of structure determination by diffraction methods. The program material reviewed below was ~rovidedon two DOS 3.3 AD& dipk r t t t i with no acccmpnnying printed durumrntntiun. Noderrriprmn oi p u s ~ h l adocu-
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(Continued on page A234)
Summary Ratings: Reviewer I Ease of Use Subject Maner Contern Pedagogic Value Student Reaction
Volume 63
Good
God
Below Average Below Average
Goad
Poor
Number 9
Average Good-Average
September 1986
A233
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