Peter Pezaro. Emanuel Mazor, and David Samuel Departments of Isotope Research and Science Teaching Weizmann Institute of Science Rehovot. Israel Nava Ben-Zvi Everyman's University Tet Aviv, Israel ~~~
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The Chemistry hyf Racks and Minerals A new interdisciplinary curriculur?~ for secondary S C ~ O O ~ S
There have been many attempts to make the teaching of chemistrv more relevant both in Hich School and at the university and consequently more attractive to students, in face of the strong competition from other disciplines. This has led to the production of many interdisciplinary courses, linking chemistry to other fields such as hiology, industry, or the environment (I).Most environmentally oriented curricula are mainly concerned with pollution or with hydrology--since the chemical aspects (2) of these problems are, in a way, easier t o teach and to understand. The earth's crust, is however, composed of a great variety of rocks varying from magmatic to sedimentary rocks, examples of which are accessible to study. Due to the need for replenishing mankind's resources-some aspects of geology have alreadv become most relevant to modern societvranging from prospecting for oil, and metal ores, to the search for materials for construction. Finally, the extensive coverage on television and in the media on the rocky surfaces of the moon and of Mars, has again emphasized the importance of geology, as a basic science, and aroused interest in the structure and comvosition of the earth (3)and its neighbors. Most 1sraeii schools, like many of those elsewhere, spend one or two days every semester on outings to various parts of the country. Since these occasions can also he used to learn about the chemistry of rocks and minerals, a new interdisciplinary course has been designed for the 10th and 11th Grades (16-17 year olds) combining Chemistry and Geology. Course Outline The course which was written (4) and tested recently in Israeli Schools combines the two disciplines, chemistry and geology, in an educational setting, in accordance with hoth discivlinarv and didactic dictates. The development of the basiiconcepts of curriculum by chapters is shown in Figure 1.The course starts with an introduction to a number of peochemical case studies aimed a t acquainting the students with the ideas and problems of geochemistry. The various chemical techniques used for identifying ions, which will he found in rocks and minerals are then discussed, allowing the student time to assimilate a new frame of reference and to encourage his awareness of geolom as a discipline. He is then thrust into his first the main ohiect of the course-the --- - - confront&on%th ~ -~- - rocks (Chap. 3). For this purpose, we have used a small boxed kit with 12 "unknown" rock samples,' identification cards and basic identification equipment-a nail, a magnet and a plastic bottle containing 5% HCI (5).The cards, which refer to 12 different rock types, hear a written text and a space designated for attaching the correct sample in a small plastic hag. They are joined in concertina fashion so as t o he suitable for wall dis~lav.This kit has. incidentallv. been found to be universallv appeaiing, not only to the high school students for whom this course was designed. hut also to a verv wide range of individuals from ten-year-olds to adults. ~t this point Fn the course, the student has all the necessary skills with which to begin ~~
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1 Limestone, dolomite, chalk, marl, shale, sandstone,a n t , gypsum, rock salt, granite, basalt, schist.
Figure 1. The development of lhe basic concepts of lhe course, by chapters.
geochemistry-i.e., he knows something about rocks, he is able to deduce their mineral composition, he has a number of powdered minerals for comparison and the chemical tools for analyzing them. He can, by now, also deduce the geological environment in which different rock types were formed, and knows to use these deductions in order to understand eeological history of actual situations in the field, or of geolo&al cross-sections presented to him in the classroom. An important aspect of this stage of the program, is a one-day field trip devoted to geological and geochemical topics, to ensure that the knowledge gained in the laboratory can he applied to real situations. The closine.. chapter . (Chap. 9)of the course, is devuted to the quest ion of raw minerals of natural resources and L O the effect of their exvloitatiun on the environment. This chapter has relevant ove>tonesin most countries of the world, which are becoming rapidly and increasingly aware of the problems of pollution of the environment and of ecology in general. The Return to Qualltatlve Analysis The highlight of the "in-school" part of the course is essentiallv the aualitative analvsis of the samples in the lahoratory (Chapter 4). In many countries, including Israel, there has been a trend in recent vears to delete aualitative analvtical chemistry from the curriculum hoth in school and at the Universitv. Nevertheless, many chemistrv teachers and instructors feel that the virtual abandonment of this subjectonce the mainstav of introductory chemistry-is to he regretted. A reintroduction of some~aspectsof analysis seems
Volume 55, Number 6, June 1978 1 383
quivocally, as those that liberate COz from heabstahle Na2C03. At the same time, silicates are converted to a form which can then be dissolved for analyzing the cations.
warranted and hv all accounts students eniov it...narticularlv when the analysis of minerals is treated as a means to an en2 and not iust as an end in itself. The Droeram described here provide; an excellent opportunity f i r &dents to learn the elements and the logic of qualitative analvsis as an important step in the study of;ocks.~herehave bekn, indeed, some recent suggestions that inorganic analytical techniques could he applied to water, soil (6),or pollutants (7). In our program, each student is supplied with ground powder samples of minerals, since rocks are usually polymineralic, making i t difficult to relate a particular element (i.e., ion) to a specific mineral. Most minerals have, by definition a fixed chemical composition and provide an excellent framework for chemical analvses of a natural "unknown." -~~ Since the number of different rock-forming minerals which are found in most countries is relativelv limited. the numher of elements which require determinatfon can bk reduced to less than ten (CaZ+.Me2+.Fe3+. Na+. CuZ+.carbonate. chloride, sulfate and phos
