John Dunstone
Canberra College of Advonced Education Conberro, A.C.T., Austrolio
A Course in Chemistry of Silicates for Beginning Undergraduate Students An interdisciplinary study
Colleges of Advanced Education are new on the Australian educational scene. Their purpose is to diversify the educational opportunities available for students wishing to undertake courses at the tertiary level. Courses are designed to meet the requirements of employer groups in a changing society, to allow some breadth of study outside chosen specializations, and to encourage interdisciplinary approaches to higher learning. The School of Applied Science at the Canberra College of Advanced Education has, as one of its main themes for study, the utilization and conservation of Australia's natural resources. This provides a good platform for the introduction of interdisciplinary courses. The courses a t the Canberra College are formed by students electing to study combinations of units from among those offered by the School of Applied Science and by the other Schools within the College, viz. Administrative Studies, Computing Studies, Liberal Studies and Teacher Education. In order to establish a true interdisciplinary character in these courses many of the component units must also be structwed on an interdisciplinary basis, their various parts must be effectively integrated, and their application to the students' programs clearly defined. This can be achieved often by adopting a "team-teaching" approach. While this method is satisfactory in some instances, particularly those involving field studies where the field work itself provides a unifying theme, it can he equally unsatisfactory in other cases when there are too'many participant instructors and adequate coordination between them becomes difficult. Such situations arise in the teaching of laboratory-based subjects such as Physics and Chemistry and in new institutes (such as the Canberra College which is now only in its third year of operation) where there are few permanent academic staff and considerable outside assistance is needed. By introducing a unit on the Chemistry of Silicates to first-year students, in their second semester a t the College, an interdisciplinary unit has been produced and an attempt has been made to overcome some of the difficulties of the "team-teaching" approach; the unit was taught by a chemist with constant advice from members of the Geology staff who attended all lectures, tutorial, and practical classes. This method of instruction was used because of our belief that it is best for a chemist to teach Chemistry whether i t be Geochemistry, Biochemistry, or Environmental Chemistry provided that adequate advice
362 /Journal of Chemical Education
from professional scientists in relevant disciplines is ohtained. This unit was designed (1) to broaden the base upon which students majoring in Chemistry can build their courses; the chemistry of earth materials
selected because it is that area of Chemistry which is most often omitted from undergraduate curricula (2) to illustrate how some of the principles of chemistry taught in an introductory single semester unit, are applied to real situations (3) . . to serve as an introduction to eeochemistm for students majoring in geology was
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The unit consisted of one session a week for sixteen weeks (one semester) and was structured as follows. Each class commenced by two students giving 5-min talks about a mineral of their choice. In general, one student discussed the chemical aspects and the other the geological aspects of their topic. The talks were followed bv a 5-10 min discussion oeriod. A 1-hr lecture was then given and this was followed by a laboratory tutorial session of about 2 hr duration. A ~roportionof the time available in these laboratory-tutorial sessions was allocated to the construction of three-dimensional models of silicate minerals, hut most of the "research" needed to complete the project and much of the actual construction work had to he done outside class time. Details of the use made of molecular models in this unit are given elsewhere.* The lecture and laboratory-tutorial topics are set out in the table. Comments
The unit has been presented twice with 20 students electing to study it on each occasion. Although evaluation is difficult because of the small student numbers there was little doubt of the enthusiasm of staff and students alike. The performance of the students appeared to be better than that obtained byethese same students in the earlier introductory chemistry unit. This was particularly noticeable in topics which are normally considered difficult for college students, i.e. phase separations in complex binary and ternary systems, interpretation of X-ray diffraction patterns, etc. 'Dunstone, J. R., J. Geol. Educ., 20,88 (1972).
Topics Covered by Course
Lecture Promam
Labaratow-Tutorial Pmeram
Class number
Class number
1 The distribution of silicon and the few related elements which comprise the continental crust-silica and the silicates. Ionic crvstal radii. radius ratio.. coordination oalvhedra, crystal. coordination numbers, Paulinp's &I&
1 Packing of oxygen and silicon atoms, replacement of Si by Al, radius ratios and crystal coordination numbers (laborat a w exercise).
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2
3-4
5
6-8
9-11
12
tures. The tetrahedial coordination of oxygen to silicon. The linking of silieon-oxygen tetrahedra. Isomorphous replacement. Ions associated with silicate structurestheir ionic radii and the consequences of replacement. Chemical classification of silicate minerals-divines, pyroxenes, amphiboles, sheet minerals, three-dimensional structures. Calculation of mineral type from chemical analysis. Structural classification of silicate minerals based on the various methods by which silicate tetrahedra are joined. Independent tetrahedra, ring structures, chain structures, band structures, three-dimensional structures. Crystalline, cryptocrystalline and amorphous silica. Relationships between atomic structure and observable properties, i.e., cleavage, hardness, fracture. Relationships between crystal form and the arrangement of atoms within a crystal. X-ray diffraction and structural crystallo aphy. Crystal symmetry, space lattices, unit cells, anfseven crystal systems. Lattice planes and Miller indices. Phase equilibria. Simple binary systems--euteetics, solid solutions. Complex binary systems-utectic plus solid solution, double eutectic, eutectic with incongruent melting, solid solution with minimum melting point. Ternary j\sremi-~rian~ulsr roordinnrri, rnrce-dimensional reprpsrnrnrions wirh temperature surfaces. .rmpltflrrl olanar rroresentations. Factors ewernine the rrvstallirn:ion of ;Gks and their constituen
