EDUCATION
Course Package Applies Modern Technology to High School Labs CHEMPAC computer-based system bridges the gap between textbook chemistry and the lab to provide greater quantitative accuracy to lab James H. Krieger, C&EN Washington
Various observers have noticed what they see as a disturbing gap that has developed in high school chemistry. On the one hand, there is the precision and quantitative nature of the chemistry course and textbook. On the other, there is the often "touchy feely," qualitative approach to laboratory work. Howard M. Saltsburg, a professor of chemical engineering at the Uni-
;e versity of Rochester, is among those p who would reject two ways that gap .e might be overcome: dropping the ilabs or converting to computer simrs ulation. He sees what he considers g the only other alternative—applying y new technology—also as the only appropriate one. What is needed in n high school labs, he figures, is a "word processor approach/ 7 That approach now has taken the Le form of a new, unique high school D1 laboratory course package called d CHEMPAC. Evolving from the uniiversity's approach to chemical enigineering lab, it was devised by »y Saltsburg and two colleagues at Rochiester, associate chemical engineerring professor Richard H. Heist and d instructor and director of undergradiuate laboratories Thor O. Olsen. i. They developed the concept in col1-
laboration with E&L Instruments, New Haven, Conn., a subsidiary of Interplex Electronics Co. that has specialized primarily in electronics and microcomputer teaching systems, In explaining the CHEMPAC concept, Saltsburg emphasizes that although the "touchy feely" approach is an important component, chemistry is quantitative as well. Since the mid-1960s, high school chemistry texts, influenced strongly by physical chemistry, have become very quantitative. But laboratory practices haven't kept pace. The object of the lab, Saltsburg points out, should be to introduce techniques to reinforce texts, teach the scientific method, develop observational skills, and the like, Others besides Saltsburg have made similar observations. For ex-
Experiments involving pH exemplify CHEMPAC approach The CHEMPAC manual provides a e large number of experiments that are to quantitative yet simple and easy to y complete in a high school laboratory period. Experiments are grouped by type. s. For example, one chapter on pH studjies includes experiments dealing with th properties of acids and bases, deterrmination of hydronium and hydroxide le ion concentrations, titration of acids is and bases, preparation of a standard rd acid solution, and the hydrolysis of Df salts. Among them: • The first experiment is designed jd to acquaint students with general feaatures of acid and base solutions. Stuudents observe the effects of acids and id bases on indicator solutions, litmus JS paper, and pH paper. Relative reacction rates of two different acids with a variety of metals are investigated. Reeaction of calcium carbonate with hyy-
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February 3, 1986 C&EN
drochloric acid is examined. Finally, a neutralization reaction is carried out as a qualitative titration involving sodium hydroxide and hydrochloric acid. Time required is about 60 to 80 minutes. • Another experiment introduces a more quantitative method for measuring hydronium ion concentration, the pH electrode. Students must first calibrate the pH electrode using a series of three standard buffer solutions. Students then use the calibrated pH electrode to measure hydronium ion concentration of a strong and a weak acid. Using the information obtained for the weak acid, they determine the ionization constant. Time required is about 60 to 80 minutes, • A third experiment calls for students to standardize a hydrochloric acid solution by titration against a known amount of sodium carbonate. This ex-
periment reinforces the importance of calibration and standardization; it provides additional practice with titration methods and pH electrode methodology; it requires both weighing (gravimetric) and volumetric methods for the standardization; it is a double endpoint titration; it illustrates two different kinds of end points (one broad, the other sharp); and it exposes students to more-complex solution chemistry. Time required is about 60 to 90 minutes. A challenge-level experiment in which the results of the standardization are used to determine the total acid content of vinegar adds 60 to 90 minutes. • Still another experiment introduces students to the concept of hydrolysis. They use the pH electrode to measure the pH of eight different salt solutions. Time required is about 40 to 60 minutes.
ample, an American Chemical Society Chemistry Education Task Force surveyed the whole of chemical education and noted that high school laboratory exercises are slowly disappearing (C&EN, May 7, 1984, page 34). In many schools, it found, the only opportunities afforded students to observe the phenomena of chemistry were demonstrations by the teacher. For some educators, computer simulation of lab exercises has seemed a way out. But chemistry is an experimental science, the task force stressed, and simulation is not a desirable or effective substitute for direct experience with the behavior of chemical systems. That doesn't mean, however, that computer technology shouldn't be applied to laboratory experiments, the CHEMPAC developers point out. And, indeed, a computer is central to the CHEMPAC concept, leading to Saltsburg's word processor analogy. The CHEMPAC system uses an integral personal computer as a sensing, measuring, and data recording tool. No programing is required, nor is there a need for any electronics expertise. As with word processing, Saltsburg says, the computer provides a transparent interface between the user and the objective— writing, in the case of a word processor; the lab experiment, in the case of CHEMPAC. The experiments are real and the results are real, Saltsburg emphasizes. There is no simulation. Supplied with each CHEMPAC package is a C-64 Commodore computer, along with a monitor, disk drive, and Citizen dot matrix printer. Experiments are tied to the computer through an interface module. Saltsburg says that this computer has a good deal more computing power than it is often given credit for. At the same time, it is inexpensive enough, he notes, that if it is damaged, "the world won't come to an end." Software consists of two floppy disks—one for the student and one for the teacher. In addition, a manual provides a complete laboratory course, including traditional qualitative and descriptive experiments. It contains introductions to pertinent chemical and instrumentation
CHEMPACpackage, including computer, costs $2200 principles, suitable for use in prelaboratory discussions. In addition, a teacher's manual includes questions suitable for postlaboratory quizzes. The teacher's manual also includes additional, challenge-level experiments that can be given to the more capable students. Equally important is the instrumentation and equipment designed by the developers for high school lab use. All equipment needed that would not normally be expected to be available in a high school lab is provided. Included in the CHEMPAC package, for example, are a pH meter, calorimeters, colorimeter, pressure sensor and vessel, EMF cell, thermistors, thermocouples, vessels, containers, and accessories. The complete CHEMPAC package—including computer, software, manuals, equipment, and instrumentation—is suitable for two students, E&L Instruments says, and sells for $2200. The equipment and instrumentation are designed to address various aspects of the problems with high school laboratory work. For example, Saltsburg points out, sensors frequently used in high schools are often too crude to give results accurate enough to correspond to quantitative textbook information and thus reinforce learning. An example is thermometers for measuring temperature. CHEMPAC uses
thermocouples and thermistors, which are accurate to 0.1 °C. CHEMPAC provides a total of 52 e x p e r i m e n t s (six are computerrelated), with about 30 of these using the CHEMPAC modules. The modules are used for, among other things, kinetics experiments, equilibrium experiments, chemical analyses, pressure/volume/ temperature experiments on gases, vapor press u r e / t e m p e r a t u r e measurements, and studies of heats of fusion, solution, reaction, and mixing. Students performing an experiment are guided by the computer through screen prompts and explanations of procedure, while the computer monitors performance for obvious errors. For experiments using the CHEMPAC modules, the computer also handles data acquisition and reduction. The CHEMPAC developers point out that with the computer eliminating the need for special instrument-related knowledge and removing the drudgery of repeated measurements and calculations, a student can focus his or her time and attention on interpreting the results and establishing the connection to the chemical principles involved. As Saltsburg notes, the computer obtains the data but doesn't provide the implications. That's up to the student. • February 3, 1986 C&EN
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