V: General Chemistry Laboratory Chairman: H. A. Neidig, Lebanon Valley College
Plenary Lecture: The General Chemistry Laboratory Speaker: Jay A. Young, Auburn University Quite properly, many of the papers a t this conference have dealt with unner level laboratorv work. But in so doing tacit suggest&s have been madeon the importance of teaching chemistrv to chemistrv maiors. On the other hand, when we cons;der the freshman laboratory, i t is appropriate to remind ourselves, for emphasis, that those present a t this conference and our colleagues elsewhere in fact constitute a minority group. To begin, then, we need a basic postulate on the purpose of the first year of collegiate education. I posit that the purpose of this first year is to help the students make the quantum jump in their interactions with an environment which is radically different for them, or is so interpreted by them, and to meanwhile teach them as much chemistry as possible. I suggest that it does not make tw much difference how much. or which narts of chemistrv. we teach to freshman-later on they can quickly accom: d i s h what is omitted if thev survive the first year. This is not to say that the chemist& we teach is in any sense inconsequential; i t is rather to assert that the needs of the individual freshman student are paramount. If we should give the student an opportunity to become an individual. and since at large institutions we must necessarily teach laboratory throlgh an interface of graduate student teaching assistants (GTA's), then we have a orohlem. This leadsto another postulate: It is desirable to set only broad limits of what must he done and what is not to hannen for the GTA's and to then within that broad area both full responsih~lityand authority to the GI'A's to ram our [heir reswnaihil~riei.Uifferentlv put. nrt~fessors cannot make the GTA into a carbon copy bf thkmselves; attempts to do so which are recognized as such by a GTA will stultify. Therefore, give the GTA's a relatively free hand; more than 95% will perform in a superior manner, especially if they understand your spirit of interest in individual student mastery of some chemistry. A few ~ e r s o n a lbiases also should be revealed. Since it is impossible in most systems to correlate lecture and laboratory. no effort should be made to do so. Further, if the same topic is treated in both, a separation of presentations in time will make the second event a review of the first, thus tending to reinforce what was learned that first time. Many prefer to grade laboratory work on a 160, or perhaps 150, point scale. Such scales have two or three significant figures, hut ultimately, the student will he evaluated on a five point, letter grade, scale. Why go to the trouble to establish a grade scale which is precise to something like one part in one hundred, especially since it is troublesome to do so, when at the end of the term most of that information is to he discarded? I suggest that a five point scale is used initially. We use "brownie points," from zero to four, for example. It is indeed mentally painful to reduce a scale from, say, 100 points to five because one is aware of the rejection of what appears to he valid information about student evaluation, but the effort is also purging and is recommended. Thirdly, my bias rejects the use of unknowns in the laboratory. Such an unknown is definable as known to every-
one except the student. This is not what real chemistry is really like. Indeed, by evaluating a student's degree of success with an unknown, we probably can reach valid conclusions about that student's excellent, or otherwise, lahoratory technique. Although good technique is indeed essential for chemists, there are other things to be concerned about, especially when a very small minority of our freshman students will hecome chemists. I sueeest that in addition to onlv reasonable nroficiencv in lahG;atory technique, these oth& kinds of goals have dace: The development of skill in meticulous. careful, and accurate obserGation; some ability to design an exper: imental investigation; some practice in the interpretation of data; and an ability to communicate the results to others. These apply to any lahoratory work. In an educational environment, we usually add efforts to illustrate chemical principles and concepts. And, pervading throughout the entire system, I suggest an emphasis upon safety and the development of the habit of concern with respect to safe practices. Of these several goals of instruction in the general chemistry laboratory, we have worked on two, technique and experimental design. Our work ( I ) has demonstrated to our own satisfaction that substantial fractions of time a t the lahoratory bench can he saved when the students are first instructed in the fundamentals of selected techniques. The presentation is multimedia with audio tape, slides, and a printed booklet (2). We have a distinct preference for slides over movie loops and TV tapes because by their nature slides tend to help the student pause while the details are examined. Movie film and TV tapes can he held on a single frame, indeed, hut few students tend to use these media in this way. Additionally, a set of slides and audio tape is more readily edited or up dated than either of the other two media. Slides and audio tape with a booklet are more adaptable, by local editing, when used a t another institution. Literally thousands of hours are required to prepare instruction in any of the multi-media, and some of this time can be saved locally by using parts of multi-media originally prepared elsewhere. Having been instructed in technique, and now spending less time in performing a laboratory self-demonstration (a cookbook exercise) students have more time to work on answers to more interesting questions. We use the module annroach and our locallv written modules contain some segments of lahoratory work presented with a minimum of exulicit directions. Students fill such gaus either by imitating some of the prior directed steps: &en in the module, by imitating what they think a student a t a nearby lahoratory station is doing, or by designing an approach of their own. The two most successful modules, for us, involve a challenge to devise one's own solubility rules based on observations from a series of directed tests and followed by open ended tests of the rules; and the determination of pi from laboratory data, some of which is recalcitrant unless the student designs the steps to he followed with some attention to chemical logic (3). At other times students are encouraged and assisted by Volume 52, Number 1, January 1975
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the GTA's to carry out a brief (30-60 min of extra time typically required) further investigation based upon the assigned module. These are couched as "Suggestions for Further Study" in the published version of the modules we also use (4). Typically, about one-third of the students will elect this extra work as an option, no doubt encouraged to some extent since this is the only way to earn an "A" grade in our laboratory course. In each instance, students cany out their work with a stated question known to them, and emphasis is placed more upon attempts to answer that question than upon the quality of the results obtained or upon the interpretation of the data. In the limit of a maximum of 60 min of extra time available, only limited additional objectives can be achieved. Opportunity is provided a t least once per quarter for a more extensive challenge in designing an experimental investigation, in which each student attempts to answer a different posed question. The questions are taken from a published source (5) and typically demand from 5 to 10 hr of lahoratory bench work plus even more time spent with reference sources to plan the work involved. One example will illustrate this part of the instructional strategy: Using 0.1 M solutions a student is directed to add a few milliliters of tin dichloride to an excess of mercury dichloride. Following that, the converse, a few milliliters of mercury dichloride to an excess of tin dichloride. In the first case a white ~recipitateforms. and a dark mav. ~recioitate in the . . second. he student i s required to account for the observations by stating a testable "hypothesis" and to then design a laboratory bench test of-that explanation. Typical
testable hypotheses involve oxidation-reduction or mass action and concentration effects, or combinations of these. Complete tests to verify an hypothesis are not required. At the simplest level, a qualitative identification of the precipitates is acceptahle; a t a higher level, a student might investigate the characteristics of half-cells containing mercury and tin ions in various oxidation states. T o some extent, these more extensive challenges provide for attention to careful ohsewation, data handling and interpretation, preparation of a written report, and illustration of principles. No doubt it could be argued that one or more of these deserves stronger emphasis in the general chemistry lahoratory than our choice of experimental design and laboratory technique. Although we intend to explore ways to increase our emphasis upon those we now have put in second place, both lahoratory technique and skill in experimental design are certainly desirable for science majors, while a student's experience in the design of an experiment to answer a laboratory question might be said to be the single crucial concept nonscience majors should carry away from their lahoratory course in chemistry. Literature Cited (11 Hill, Brenda W.. Ed. D. Thesis "An Evaluation of Audiouisusl Slido/Tspe Units.. . in College General Chemistry Laboratory Instruetion," Auburn Universrty, 1973. I21 Young, Jay A.. and Fkl, Nicholas J.. "Chemistry Pnpuatian Laboratory," McGraw Hill. New York. 1913. I31 Young, Jay A,, J. Coll. Sei Teach.,2.28 (19131. a (41 Neidig, H. A , 1Eduorl "Modular Laborstmy Program in C h e m i s ~ y "( ~ a r i o ~mad. vlssl WillardGrant Press,Boston. M a s . . 1970 land following years). (51 Young. Jay A.. "Practice in Thinking." Prcntie-Hall Inc.. Englewmd Cliss. N.J.. 1958.
Contributed Papers Developing Independence in the General Chemistry Laboratory
John E. Davidson, Eastern Kentucky University, Richmond, Kentucky One reason for the lack of success that many beginning students have in general chemistry is their inability to work independently. This may come as a result of their "underpreparedness," which could include a lack of opportunity to perform "open-ended" experiments. It almost certainly involves a lack of opportunity to make mistakes in a minimum-stress atmosphere. The general chemistry program a t Eastern Kentucky Universitv involves some 300 students in sections of 24 each. he program has been developed to encourage the students' inde~endencein the l a h o r a t o ~ This . has led to (1) upgrading t h e students' level of profkiency in auxiliary areas, such as mathematics, which are.generally considered necessary for success in chemistry; (2) improving the handling of data in the lahoratory; (3) allowing the students to carry out experiments a t their own pace with enough time to redo the experiments if the results seem to turn out "wrong;" and (4) encouraging the students to design and carry out their own experiments under staff su~ervision. A combination of mini-courses (uia audiotape-slide combinations and/or videotaped lectures), simulated experiments, and open-time has been used to accomplish the above goals. The results have been both encouraging and puzzling. Encouraging, because the general level of proficiency of the students has noticeahlv increased and some students have "turned on" to experimental chemistry, hut puzzling because most of the students, while enjoying the lab work, 42
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have stayed away from designing their own experiments, sometimes a t the expense of their grade.
A General Chemistry Laboratory Program Based Upon the Premise that Conceptualization Isn't All That Easy for Many Students
Mary L. Maier, C.S.J.,Medgar Evers College, Brooklyn, New York It is evident that students enrolled under the open admissions policy in the City University of New York vary widely with respect to their previous educational experiences. Those who are admitted to the freshman chemistry program generally lack the requisite facility in conceptualization. A laboratory program providing an additional experience in and reinforcement of basic concepts which must he understood by each student in his own terms is here proposed. Fourteen topics considered difficult by these students are the subject matter of the program. Topics like density, the mole, equivalent weight, and so on, are presented in a two-week sequence. The first week presents problems related to the concept and provides the students with simple materials by means of which they can solve the problems and deal with the concept on a non-technical level. The second week's laboratory is directed toward the solving of a typically scientific problem related to the concept. Both laboratory sessions incorporate the teaching of proper techniques, use of calculators to avoid time-consuming computations, and opportunities for individual review of concepts and techniques hy means of slides and tapes. However, the primary objective is the use of laboratory time to maximize learning experience geared to the unique needs of these students.
The Project-Oriented Freshman Lab-How Structure is Enough?
Little
Joseph G. Gordon 11, California I n s t i t u t e of Technology, Pasadena, California To provide students with a research-type experience early in their careers, the freshman chemistry lahoratory a t Caltech (enrollment: about 230) has been transformed over the past several years from a highly prescribed quantitative analysis course to one consisting of flexible, openended projects. Students are exposed to a range of prohlems and given access to a variety of instruments, equipment, and supplies and are expected to find (with guidance) their own experimental pathways to solutions. In general, this approach works well. However, for some students more structure is required and many well-defined, explicitly described experiments are maintained.
A Single-Project Laboratory Course tor General Chemistry
Emily P. Dudek, Brandeis University, Walthom, Massachusetts The following integrated sequence of experiments offers advanced students (four sections of 15 students) in general chemistry a logical, coherent attack on synthesis and analysis, an element of unknown, a variety of useful, current techniques, and a satisfaction of completing successfully a meaningful project. Nevertheless the experiments stay within the limits of time (twelve 4-hour periods) and theoretical background of the students (one lab course is scheduled for students from several, diverse lecture sections). Compounds, [Co(NH&]C13 (orange) and [CO(NH~)~CI]C (purple), I~ are prepared from CoC1~6Hz0 and purified, illustrating synthetic techniques which include suction filtration and recrystallization, and showing that two substances are obtained from the same reagents combined in different proportions. The two complexes are analyzed and characterized by methods pooled from puhlished procedures but judiciously selected to be current (no gravimetric analysis of cobalt or chloride) and varied (no repetitive titrations with indicator endpoint for Co and NHJ and C1). I , Optical spectra uf aquwus ~ ~ U I Cumpare I O ~ . with spectrum of crnnmerr~alsample fur crude acxasrnenr of purity. 2, 1)erermmarlm of %(:u b\ phornrhem~cal reduction and spectrophatometric measurement of the resulting CO(NCS)~Z-, and/or by electrodeposition. 3) Determination of %NH3 by distillation and back acid-base grauimetric titration of distillate. 4) Determination of %CI bv oassine an aoueous solution down a cation-exchange eolu& and conduchnetric titration of the effluent and by potentiometric measurements using specific ion electrodes 5 ) Magnetic susceptibilities of solid samples using a Faraday balance. Compare values with those of other Co(IIl) and Co(1I)salts. 6 ) Ionization in water as measured by (a) Conductivity, and (b)Cryoscopy 7) Kinetic study of the hydrolysis of [CO(NH~)ICI]CI~ using a spectrophotometer. 8) Conversion of [Co(NHa)sCI]Clnto -NOz and -ON0 linkage isomers asdistinguished by infrared spectra.
Cookbook Versus Creativity: An Innovative General Chem Lab Program
C. Venkatachelam a n d R. W. ~ u d o l p hUniversity , of Michigan, A n n Arbor, Michigan While i t is generally accepted that lab instruction is an important aspect of chemistry education, it is our experience that many undergraduate lab programs suffer from a
singular lack of direction. Obviously in the lab we want the students to learn more than the knack of following directions in a manual. Yet very often this remains the sole behaviorally stated objective of lab work, especially in general chemistry lab programs. In this department we have defined a set of laboratory objectives and devised a new approach to them which involves a cyclic lab program. Under this motif students are first presented background knowledge and necessary skills in a learning phase; they are then faced with an openended challenge in the same subject area for the next phase of the unit of instruction. Thus, research design and logical deduction are introduced into the lab. This scheme was first piloted in our general chemistry program for one term (-300 students); it seemed to serve well the needs of our students who come from many different disciplines and have widely different backgrounds and interests. Extensive evaluation showed the effectiveness of this new approach and it has now been adopted on a larger scale (-1300 students).
New Freshman Laboratory Course for the Science Majors at Louisiana State University, Baton Rouge
Buddhadev Sen, Louisiana S t a t e University, B a t o n Rouge, Louisiana Most of the important aspects of laboratory instruction in chemistry have been covered by the papers already presented a t this conference. It is now evident to most of us who have been attending this Conference that the curriculum content is only . a Dart . of the story of the freshman lahoratory program; in fact, several sets of pedagogically sound curricula can be evolved. Consensus seems to be that the crucial factor in instructional success (as measured by the success rate of the students, or some other device), mav be the oreanization and nresentation of the program; and I completely agree with this consensus. The freshman chemistw lahoratorv nroaram a t LSU-BR is new only in the sense ofirganizatioi&presentation. The importance of the role of TA's has been emphasized by Professors Lippincott, Bell, Young, and several others. During the last three years we have taken a number of steps to generate a positive attitude among the TA's, and to obtain their more active involvement. This has definitely improved the program as indicated by students' success rate as well as their evaluation. Starting with one a t the very beginning of the semester, we have three to five very intensive workshop sessions with the >
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We have also been making increasingly greater use of slides and loops. The importance of all kinds of visual and audio-visual aids has been emphasized throughout the conference. I shall add only a few words regarding the course content which will be published as a manual by Burgess next August. Experiments are simple but related to students nhvsical world either accumulated exoerience of the . through the classroom or due to a simple growing up. Considerable emphasis has been placed upon the theory; the objective has been to impress that experimental procedures are not Betty Crocker's recipes. Enthusiasm of the undergraduates is extremely sensitive to the arithmetic of credit hours. Chemistry is an experimental science; I have never found any explanation why there are fewer per hour credits in a laboratory course than in a lecture course. The distorted message read by many students is that the lahoratory course is a penal colony for those who have committed the crime of taking chemistry, willingly or not. A lahoratory course must he given its proper recognition in the curriculum. If experi-
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mental work is important, then we must tell it to the students (as well as professors who are in charge of the lab programs) in the language they understand; not a word has been said on this point so far in this conference.
Chaos, Creativity, and Choice: A Minimally Structured Non-Science Majors' Laboratory
Jane E. Copes, and Daniel J. Macero, Syracuse Uniuersity, Syracuse, New York Non-Science majors are rather special sorts of people. We often encounter students who are terrified of science and scientists in the same class as people who have had four or five years of sciences in high school. Their needs are so vastly different that some procedure for letting students find their own levels of competence must he available before we can even begin to consider trying to change their concepts of scientific knowledge. In motivating students in a non-science oriented laboratory, we need to present laboratory experiences that are challenging as well as fun. To realize this we have evolved over the last three years a loosely structured lahoratory course in which a large number and a wide variety of experiments are offered. The individual student selects from this list the exoeriments (s)he . , is interested in with the result that many experiments are happening a t the same time. Despite this seemine chaos. however. we feel that letting stidents choose th& own' paths of experimentation and interest does accomplish our aims. A lot of us understand that all of our students are not ready to learn exactly the same things a t the same time. Putting that understanding into a lahoratory framework is an exhausting hut exciting task. But i t can he done!
Quantitative Analysis in the General Chemistry Course
Clarence G. Johnson, Christian Brothers College, Memphis, Tennessee There is a trend in chemical education to move quantitative analysis into the general chemistry course. Such a change results in the elimination of some of the usual general chemistry lahoratory experiments. More importantly, one must question whether quantitative analysis can be adequately understood and mastered by most students in general chemistry. The author has made a study of student performance in the lahoratory regarding operations associated with proper quantitative techniques. In particular, common errors involving titration, pipetting, weighing, quantitative transfer, handling of reagents, cleaning of equipment, calculating, and reporting have been observed and evaluated. Information has been obtained for students in the freshman science majors course (50 students per year), the nonscience majors course (80 students per year), and the quantitative analysis course (10 students per semester). These observations of student lab technique indicate that most students, even though instructed, do not retain proper techniques. It is also concluded that the students do not grasp the concepts associated with quantitative analysis in the general chemistry course. The author proposes that the general chemistry course should consist of proper techniques, with an expectation of semi-quantitative results; and that a more rigorous advanced course in quantitative analysis he retained in the curriculum of chemical education.
Meaningful Quantitative Experiments in General Chemistry
Leonard F. Druding, Rutgers Uniuersity, Newark: New Jersey The Wisconsin Freshman Chemistry Laboratory Program for Non-Majors
Bassam Z. Shakhashiri, Uniuersity of WisconsinMadison, Madison, Wisconsin The lahoratory portion of our largest chemistry course (yearly enrollment of over 3000 students) was recently changed. The traditional semester-long work in qualitative analysis was dropped. Considerable efforts were devoted to the proper implementation of the new approach which was designed to integrate the laboratory experience with lecture material. Laboratory periods are scheduled such that students are familiarized with terminology and concepts in the lecture prior to performing experiments. The experiments are designed to introduce the student and stimulate his interest in chemical systems and their properties. The general approach is to enable the student to develop certain minimal skills and techniques that are necessary to the performance of scientific experiments. The intention is not to train chemists or technicians, but to provide necessaw tools for the ~erformanceof meaninpful'experimenrs. he experiments'are such that they all,;; considerable rwm for imacinative thinkinr! .and individual design on the part of the &dents. The "non-cookbook" format of the experiments has Droven to he a beneficial challenee to students. Various innovations (written pre-lab assignments, lab videotapes, lab report formats. etc. . . .) have h e l ~ e denhance the student'slab experience. The structure, content, and organization of the lahoratory program was described. 44
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One of the most important topics covered in the first semester of general chemistry is stoichiometry and concentrations of solutions. After various unsatisfactory experiences with the more traditional types of introductory laboratory experiments, the Department decided to concentrate on more quantitative experiments which emphasized stoichiometry. When "quant" was first tried with commercial unknowns, student response was poor and the analytical results were disasterous. In the version now in use for three years, student acceptance and interest has been high and the analytical results have been much improved. First, in order for the students to learn proper analytical techniques and achieve good results, the number of experiments was reduced from one per week to six per semester. No attempt was made to correlate the experiments with the lecture material. Second, the analyses were changed to those of common, commercially available, or familiar products. This was done in recognition of the 98% of the enrollment in the course who are not chemistry majors, and who may not appreciate the importance of soda ash. The experiments now in use are 1) Density: by displacement and flotation: uses simple balance, graduated cylinder, pipet, and shows how experimen-
tal design can affect precision of results. 2) Specific Gravity of a Liquid: The calibration of a . o i.~ e t shows limitations of instr"ment; experiment determines %
alcohol in water.
3) Phosphates in Detergents by Colorimetry: emphasizes concentrations and dilution factors, differences in reporting re-
sults.
4) Acid-Base Titrations: techniques of titration, use of pH meter (a) Vinegar analysis (titration of a colored solution), (b) Antacid analysis (titration in presence of solids), and ( c )
(Optional)Equivalent weight of organic acid Calcium Content of Limestone: illustrates handline.. of ore. tipnates and redux reartruns. Cslrium oxslate ia farmed. separated, and rilra~pdwlth permangannre. 6 ) Thermnrhernisrry: He41uf \eutmli~arron 61
Incorporation of Structure Determination into the First Year Laboratory Program
James F . Bonk,Duke Uniuersity, Durham, N o r t h Carolina During the first semester of the introductory chemistry course (700 students) the main emphasis is on stoichiometry and structure. Two sequences of related laboratory experiments on these topics will be described. The first sequence deals with an ionic compound and consists mostly of traditional experiments. Students de-
termine the specific heat of Mg metal and then quantitatively convert Mg to MgO to determine weights of Mg and 0 that combine. They then determine the heats of reaction of Mg with HC1 and of MgO with HC1. They are given the heat of formation of H20 (I), the density of MgO, appropriate Born-Haber cycle data for MgO, and a simulated X-ray powder diffraction pattern for MgO. From the accumulated data they can find an approximate atomic weight of Mg, an exact atomic weight of Mg, the formula for MgO, Avogadro's number, the dimension of a unit cell of MgO, the structure of MgO (sodium chloride), the interionic distance, the ionic radii, crystal lattice ene r w for McO - .(from Kanustinski relation). the heat of formation of MgO, and a second value of crystal lattice enerw from the Born-Haber cvcle for MaO. -. The second sequence- deals with two covalent compounds-the two dichloroethanes. Students determine boiling points, molecular weights by freezing point and gas density, molecular farmulas (percentage composition given), and finally the structures from provided mass spectra, ir spectra, and nmr spectra.
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