H. A. Peoples. Computerized Learning Enhancements: http://www.ecis.com/~clehap; email: clehap@ecis.com; 1996 - 1997.

CheMentor: Calculating Chemical Formulae, v. 2.0

Single copy $39.95; site license fees available.

CheMentor: Stoichiometry I, v. 2.0

Single copy $29.95; site license fees available.

CheMentor: Practice Items I, v. 2.0

Single copy $29.95; site license fees available.

CheMentor: Thermodynamics I, v. 2.0

Single copy $39.95; site license fees available.

CheMentor: Toolkit, v. 2.1

Single copy $39.95; site license fees available.

CheMentor is a series of software packages for introductory-level chemistry, which includes Practice Items (I), Stoichiometry (I), Calculating Chemical Formulae, and the CheMentor Toolkit. The first three packages provide practice problems for students and various types of help to solve them; the Toolkit includes "calculators" for determining chemical quantities as well as the Practice Items (I) set of problems. The set of software packages is designed so that each individual product acts as a module of a common CheMentor program. As the name CheMentor implies, the software is designed as a "mentor" for students learning introductory chemistry concepts and problems. The typical use of the software would be by individual students (or perhaps small groups) as an adjunct to lectures. CheMentor is a HyperCard application and the modules are HyperCard stacks. The requirements to run the packages include a Macintosh computer with at least 1 MB of RAM, a hard drive with several MB of available space depending upon the packages selected (10 MB were required for all the packages reviewed here), and the Mac operating system 6.0.5 or later.

Practice Items (I) provides over 1000 exercises covering isotopes, formulas and names for ions and compounds, moles and molar masses, percentage composition of a compound, oxidation numbers, and molarity. Each section of the practice items explains what types of exercises are available and what students must know to successfully handle the exercises. Help is available in several different forms. For example, in the oxidation numbers section, one problem asks for the oxidation number of carbon in CO₂. If a student needs help, he or she can read a description of oxidation numbers and how they are assigned, consult step-by-step rules for assigning oxidation numbers, or, using the "Peek" button, see the correct, worked-out solution. The available help is always appropriate to the current section. After a student has entered an answer, pressing the "Judge" button determines if the answer is correct and provides some feedback about why an answer is incorrect. The feedback may be minimal in some cases, such as in the oxidation number example where the answer is judged correct or incorrect, or more extensive, as in the case of writing formulas for ions where the feedback points to the part of the formula that is incorrect.

Stoichiometry (I) contains about 80 problems in three categories: single and double replacement reactions (how much product can be obtained from a certain amount of starting reagent), limiting reactant problems, and percentage yield problems. Calculating Chemical Formulae offers over 75 different problems in which students determine chemical formulas from various types of data including percentage composition, mass composition, synthesis data, combustion analysis, and dehydration analysis as well as combinations of data. As an example, a problem from the Stoichiometry (I) module in the limiting reagent category is "Zinc can displace copper from copper(II) nitrate solution as follows:

Zn(s) + Cu(NO₃)₂ (aq) --> Cu(s) + Zn(NO₃)₂ (aq)

What mass of copper is formed when 0.425 g of zinc is reacted with 50.00 mL of 0.150 M copper(II) nitrate solution? Answer: _____________ g"

The student is expected to work out the problem with pencil, paper, and calculator, and then enter the solution in the answer blank. When a student does not know how to arrive at an answer, help is again available in several forms. First, there is a "Text" button, which opens a window with text that describes the general concepts involved in the current section. For the stoichiometry module the scrolling "Text" window starts with "A balanced chemical equation shows you the numbers of moles of reactants and products that are involved in a chemical reaction." After scrolling through this general information, a student could come to "First we will consider the limiting reactant approach to solving the problem. To begin you should calculate the number of moles of each of the reactants you are dealing with. This may be done by" and so on. Then there is a "Recipes" button that provides general, step-by-step instructions for solving problems of the current type and sometimes including alternative approaches. For the example problem above, a recipe for calculating a theoretical yield is given.

These text and recipe options may get some students on the right track, but probably the most helpful source of assistance is the help selections that correspond directly to the problem at hand. For the example above, a student can get help at various stages, such as finding the moles of reactants, finding the limiting reactant, and setting up the calculation of the yield. Each help window gives the data from the problem and provides answer boxes for the student to enter the result of the next step in the calculation. In the example, the "Finding Moles of Reactants" help lists the reagents, Zn 0.425 g and Cu(NO₃)₂ 50.00 mL:0.150 M, and expects the student to enter the moles or millimoles of each reagent. A "Judge" button will determine if the answer to each step is correct and provide some feedback on an incorrect entry. If the student does not know how to do this individual step, he or she can use the "Peek" button to see the worked-out solution. There is also a "Why?" button that provides some basic information about why the current step is useful in the overall problem solution.

The CheMentor Toolkit has a series of calculators for determining molar masses, molarity, molality, and pH, and for converting between moles and masses. Also included are a set of 20 recipes for solving problems and the exercises of the Practice (I) module. The 20 recipes cover more topics than the other modules and include such items as molecular weight from percentage composition, molecular weight from osmotic pressure, percentage yield of reactions, balancing redox equations, and finding K_sp from solubility data. The "molecular weight from percentage composition" recipe is, as an example, "Starting with the % of each element: 1. Assume that you have 100 g of compound. 2. Calculate the number of moles of each element in your 100 g of compound. 3. Using the number of moles of each element in your 100 g of compound. 3. Using the number of moles of each element, find the mole ratio. 4. If necessary, modify the mole ratio to make sure it contains only integers. 5. Now that you have the empirical formula, use it to find the molecular formula." Because the calculators and recipes are designed for use with problems other than those in CheMentor, they can be used for doing and checking homework problems.

The calculators and recipes are purposely not available when students are working problems in the CheMentor modules. This might help allay worries that the availability of a nice list of recipes could encourage an algorithmic approach to problem solving in which students look through a Rolodex-like list of algorithms, find the proper one, and then "plug and chug". Memorizing algorithms may not imply understanding of the concepts involved, although the recipes of the Toolkit may indeed help students get the right answer to many of the typical problems in introductory chemistry. Instructors might appreciate the calculators for their own use when formulating exam questions and writing answer keys.

A printed User's Guide is provided with each CheMentor module. The guides adequately describe the straightforward installation procedures. Each guide provides a tutorial for learning CheMentor and the operation of the individual module. Students will probably not need to look at the manual, although a brief orientation provided by an instructor might be helpful to acclimate students to CheMentor. The user's guides also provide a quick reference section and a brief instructor's guide (except for the Toolkit, which is geared toward purchase by students). The instructor's guides give some suggestions on how the software can be used with classes.

The content of the reviewed modules includes many early concepts in the typical chemistry curriculum. These modules are appropriate for students first learning the material at the high school or college level, and perhaps also as review for students expected to know most of it at a more advanced introductory level. One can purchase those modules that will be of most use; all will use the same CheMentor application. Other CheMentor modules not reviewed here can be added (an additional thermodynamics module is available). The modules address areas well suited to a computer approach. For example, whereas extensive lectures on nomenclature might not be fun for either instructors or students, this software allows students to work on nomenclature to their heart's content in an environment under their control.

The user interface for CheMentor is adequate. While the individual modules are tailored to the particular topics, they are similar in design. Navigation through the modules is via a combination of buttons and menu items on the windows and items from the main pull-down menus. Students should be able to find their way around CheMentor, although the program might seem confusing at times because it has much to it and there are different ways of accessing information. With help available in several forms, sometimes many windows (1 ¥ 10 ^{- 23} mol) are on the screen at one time while one is working a problem. To get to a new problem or another type of problem, one must press the "Next/Menu" button, bringing up yet another window with the choices "Try another", "Main Menu", and "Cancel". Fortunately, the open windows are closed automatically after a new problem is selected. A nice feature often used throughout the modules is that, rather than blasting the student with a big window full of text all at once, the student can step through digestible-sized points one-by-one, using a

"More" button. For example, the five steps in the "molecular weight from percent composition" recipe described above are displayed step by step using the "More" button. Significant figures and units are checked in the results of calculations. The calculators can use decimal or scientific notation. Some minor bugs were found in the calculators and reported

The CheMentor series is designed as an aid to learning chemistry. It does not provide a first exposure to topics, nor are the modules flashy, multimedia extravaganzas. They are straightforward, solid products that can help motivated students master concepts and practice solving problems. The modules provide sensible, practical help toward solving problems and patient feedback to student responses. They are worthy of consideration by instructors who wish to provide computer-based help for concepts from introductory chemistry and whose students have access to Macintosh computers.