Many of us are taking the first tentative steps into the wild, scary, expensive world of incorporating technology into secondary school science classrooms. Some of us, with generous funding from our school, have done the professional version of jumping into the deep end with only rudimentary swimming skills. The selection of software for chemistry has begun to expand in the last two years, and fantasies of unlimited spending capability now include a variety of software and video types to accompany those electronic balances, pH meters, and test kits that we carry around in our imaginary shopping cart. One class of software is the lab simulation, which serves a variety of purposes, not the least of which is to minimize the need to purchase so many pieces of equipment and expensive materials. But before one adds a simulation program to the curriculum, one needs to understand what these programs are designed to do (and not do).

Simulation software for chemistry allows students to perform reactions in virtual reality. The advantages of this are that reactions can be performed repeatedly while variables are changed, students may have access to a greater variety of materials or reagents than in many high school laboratories, reactions can be slowed down or sped up to be observed in a manageable time frame, or reactions that are hazardous or dangerous can still be manipulated safely. Students can select and combine reagents, set parameters such as concentration and temperature, and analyze products or graph results. No simulation can take the place of "dirty-fingernails science". Simulations can bridge the gap between textbook and hands-on laboratory experiments, or expand experiences into realms not possible in a given lab environment. They cannot take the place of real live science, where students can make mistakes and things don't always follow the rules.

Crocodile Chemistry is a new simulation program presented by Crocodile Clips. The program used for this review is obviously a work in progress, as there were features present in the menu that were not accessible in this version. The simulation allows the user to combine various reagents in definite quantities, using a broad selection of glassware and equipment. Materials include a wide range of acids, bases, metals, inorganic salts, gases, and indicators. The graphics are two-dimensional and very simple, and the materials are easy to manipulate. Temperature and other properties can be measured during a simulation if desired, and graphical portrayal of results is an option. Materials can be used in several forms, such as lump solid, fine solid, or aqueous solutions of varying concentrations, and masses and volumes can be selected in an almost infinite range of values. Once a simulation has been designed, text can be added to it to give instructions, describe the chemistry involved, or show chemical reaction equations. An animation of what occurs at the atomic level is also featured, but is not available in this preliminary version. I used the simulations that were already set up and was able to make up a variety of new ones, but could not make the probe feature work without instructions, not included with the review copy.

Many of the simulations work the same way they would in the lab. The colors are similar, reactions appear as they would right down to the sound effects, and subtle differences such as metal activity or variations in reaction rate are discernible. However, some combinations do not react in the correct proportions. For example, one triprotic acid reacts in a 1:1 ratio of volume with a monoequivalent base when the molarities are equal, and reaction of ferrous sulfate with permanganate does not exhibit the normal 5:1 ratio at endpoint. Some combinations, when heated, show no change when in reality they would, and some combinations do not react at all.

Simulations should help bridge the gap between concepts and laboratory experiences. Flexibility in quantities and forms are important, but so also is accuracy. This program is very flexible; even in its preliminary form there is so much control of quantities and concentrations, but the stoichiometry is not correct in every case. Combinations that do not react as they would in the laboratory can be misleading. As this product is a work in progress, another look would be needed when the final version is available.