M. A. Wartell Metropolitan State College Denver, Colorodo 80204
A New General Chemistry Laboratory Scheme: Observation, Deduction, Reportage
An important dual problem faces any teacher of nonmajor freshman chemistry courses: integrating coursework and laboratory work and, once the first has been handled, making the lahoratory and coursework exciting and relevant without sacrificing academic standards. These problems become even more acute when the instructor deals with a completely heterogeneous student body and realizes that student needs and goals are not those of the students of even a decade ag0.l Metropolitan State College is an urban-oriented institution which maintains an "open door" admissions policy. Thus, the students a t MSC range from very bright to marginal. This range includes new high school graduates who were not "good enough" or financially able to get into the state universities, veterans getting a n education on the GI Bill, and middle-aged people who have decided they want new skills or a different career. Our non-major freshman chemistry courses contain a similarly wide cross-section. It is a constant struggle t o make chemistry exciting and relevant to all of these students. The freshman non-major chemistry sequence now consists of three quarters: general, organic, and biochemistry. It seems that if the student can succeed in the general chemistrv section. the relevance and excitement of oreanic and h:ochemis&y are more easily assured by the n a k r e of t h e subiect matter alone. However. the eeneral chemistry hurdlesis quite high. In the past, there i a s been a 50% attrition rate during the first quarter. We have developed a new lahoratory sequence which may be quite successful in cutting this attrition rate. The lecture portion of both the old and the new course follows the outline
I. Measurements and Units Atomic Theory 111. Compounds and Chemical Bonds IV. Moles, States of Matter, and Chemical Energy v. Non-metallic Elements in the Environment VI. Solutions and Colloids W. Ionic Compounds and Heartimi WI. Aridity: Measurement and Cmrrol
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We focused on changing the lahoratory, assuming a philosophy and then implementing it. The philosophy underlying the lahoratory was that science consists of observation, deduction, and reportage. Chemistry, as one of the sciences, is also made u p of these three aspects. Thus, we chose these three skills as our primary educational responsibility. We felt that if we taught them well and applied them to chemical phenomena, we would succeed in teaching a general method of problem solving as well as general lahoratory skills and material which would reinforce the lecture. To this, we added what we felt would make the lahoratory exciting-problems that the student could solve himself. The lahoratory took the following form. Experiment I. Qualitative Obseruations and Descriptions. The student makes qualitative observations about positions of objects in the laboratory and laboratory equipment. He describes these objects and locations in as precise a manner as possible. The student is shown a system (e.g., a beaker of boiling water) and makes 100 observations about the system. He then organize the
data in such a way as to make it quickly understandable to any reader. Experiment II. Quantitative Observations. The student makes observations of length, volume, weight, density, temperature, and heat capacity. Both direct and indirect measurements are made. The concept of significant figures is presented and used with the student's measurements. Organization of numerical observations is a major part of this experiment. Experiment III. Renctiuities. Reactivities of various elements are shown through demonstrations. The concept of chemical change and energy relationships are dealt with. The student makes observations concerning elemental reactivities and propert i e of elements which are put out for him to observe. The data is then organized appropriately. Experiment IV. The Three Balloon Problem. The student is given three balloons filled with various gases, (H2, He, 02). He is asked to make as many ohsewations as he can, both qualitative and quantitative, about the gases. He is expected to find out about gases in general and determine the reactivities and physical properties of these gases in particular, using any equipment in the laboratory. Experiment I;-. Conservation of Mass and Composition of a Com~aund.The student runs the reaction Ma + 2HC1- Mac12 H; with an excess of Mg. Having carefull; weighed the reactants or known their concentrations, he weighs the left-over Mg, evaporates the solution to obtain the MgC12 and weighs it, and calculates the number of moles of HI formed from collected Hz. After working up the data, he discovers the law of conservation of mass and the formula of MgCll for himself. Experiment V I Solutions. The student is given 10 solid unknowns and two liquid unknowns and is asked to find out all he can about the relative solubilities of the substances in one another and to make general deductions about them. The identities of the substances are then revealed and the students try to justify their deductions in terms of the new knowledge. Experiments showing temperature dependence of solubility and bailing point elevation are performed by the student. Electrical conductance of solutions is demonstrated. Experiment VII. The Nine Solution Problem.2 The student is given nine solutions, told what they are but not in what order. He is asked to find out what they are by mixing them together and observing reactions. Experiment VIII Acidity. Thestudent investigates the pH and normality of five unknown acids to determine percent ionization and total concentration. pH is determined both with pH paper and a meter. The identities of the acids are then revealed and deductions concerning given acids are encouraged. The electramative senes is derived by demonstration.
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All experimental procedures are purposely vague. The student is expected to develop his own experimental procedure and data sheets before the laboratory begins. These are checked over by the instructor who makes suggestions as to where improvements might be made and then gives the student advice throughout the lahoratory. Experiments 1-111 on various types of observations lead up to Experiment N. Experiments V and VI on solutions build the background for Experiment VII. Experiment VIII emphasizes techniques and concepts and is based on knowledge gained in previous experiments. In this way,
'Walter, R. I., J. CHEM. EDUC., 49,323 (1972). T h i s experiment was adapted by the Yale University Chemistry ~epartmentfrom the freshman chemistry laboratory manual at Harvard University. The manual was written by L. K. Nash. Volume 50,Number 5, May 1973 / 361
the laboratory becomes almost a programmed learning experience. The success of the program was judged on the basis of student evaluations and enrollment statistics. Student evaluations were highly favorable. The general feeling was that an interesting challenge had been presented and that this type of "unstructured" laboratory was a new and ex-
362 /Journal of Chemical Education
citing experience. The enrollment statistics indicated a 0% attrition rate as compared to a normal 50% attrition rate: We hope that this program will continue to show good results and we are beginning to develop other laboratories on the same mode. Copies of our laboratory manual are available on request.
