original color, just as in a real lab experiment (obviously, the final color remained if the student were a t or beyond the endpoint). Or a student could manipulate the buret to titrate a t whatever rate he or she wished. Often a student would rush past the endpoint on the first attempt, but then use the "dropwise" mode near the end of the titration to obtain much better results. A misreading of the buret volumes would result in final K, error, but the student could redo the titration several times to get a hetter result. The average of the results was always calculated by the program, thus reinJohn Gelder's interactive programs Chem forcing the concern for good precision. In the case of the spreading of the fatty acid, Lab Simulations 1: Titrations and Chem occasionally the trial would fail and a mesLab Simulations 2: Ideal Gas Law (hereafter sage would be given: the experiment failed referred to as 1and 2) are intended t o serve due t o a dirty water surface-start over. as an introduction far students prior t o acSurprisingly, mast students enjoyed this tual experimentation in the chemistry laboratory. Both have thorough background infeature! Throughout Simulations 2, one observes formation and clear instructions incorporatthe movement of particles as they bounce ed into the program and thus servevery well about inside a chamber of given volume. as self-instruction modules. In addition, One observes the elastic collisions of the both could function very effectively as review modules for students who have alreadv particles with each other and the wall of the chamber. By pressing the paddle buttons, performed titrationr or gas law labs earlirr. one can vary pressure P and volume V conSimolations I has the student read the buret meniscus, select the actual endpoint, ditions and, by turning the paddle dial, the temperature T. The number of moles and determine the molarity of the acid and calnumber of particles per mole are pre-selectculate mole weight of a weak monoprotic ed and not variable during a simulation. acid. Once this is completed, the student If the student fixes the volume of the may find the identity of the unknown acid chamber, he or she can examinemathematiby an acid equilibrium constant determinacally and visually the relationship hetween tion, or determine a value for Avogadro's P and T for a fixed number of particles, or, number, or stop. In the first case, the stuupon fixing the pressure, the relationship dent reads a pH meter t o obtain the pH of between V and T. In a very short time a the neutralized acid solution and calculates student can verify the PV = nRT mathea value for K, in order t o select his or her matical relationship. Thus the program is unknown acid from a given list of acids (and corresponding K, values). In the second quite limited in keeping student interest; what makes the program interesting is the case, the student deposits a small amount of notion for sound that accomnanies the cola known fattv acid onto a water surface and liding pnrtirlesand the ability rosrlrer vnrrestimntcr the ares uf the resulting monolnyer in order to
