NEGLECTED TYPES of EXAMINATIONS G. N. QUAM
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Long Island University, Brooklyn, New York
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0 MANY teachers of general chemistry the title of this paper may seem ambigirous but according to the author's observations the types of examinations described here have been neglected. We do not lay claim to anything strikingly original; the purpose of the paper is chiefly to call attention to a useful and practical procedure. The types of examinations we wish to describe are, I. Open-book lecture 'examination; 11. Open-book laboratory examination; and 111. Practical laboratory examination. I. ' THE OPEN-BOOK LECTURE EXAMINATION
The administration of the so-called open-book lecture test introduces some obvious difficulties. I n fairness to all students the sources of reference must be restricted. One procedure is to allow each student the use of texts regularly assigned for the course and any personal notes he wishes to bring. At the outset one is faced with the problem of phrasing questions which are not directly answered in the available texts. Questions based directly on textbook material can serve a useful purpose. The student should be made aware of the apparent necessity of the appendix, and,
above all, of the usefulness of an index. The latter might be considered more seriously by some textbook authors. We have observed the amazing helplessness of some otherwise apparently good student when faced with an open-book examination. Reverse the picture and imagine the teacher, or the practicing chemist, suddenly deprived of his sources of reference when faced with the solution of a chemical situation. A certain store of factual information must be available for any eventuality, to be sure, but why not test the student during his training period in somewhat the same way in which he will be tried later? Our attempt to continue the teaching process in general chemistry while testing the student may be illustrated most easily by displaying a few typical questions. We must hasten to point out that the students are forewarned and even cautioned that the open-book test period is not a study period-the books are available for quick reference only. Typical open-book questions we have used in general chemistry are given. (1) Underline the symbol or formula of the substance in each series having the characteristics called for.
Lowest concentration of H f : 0.1N. HCtHsOn. 0.1NHzS04.0.1N HCN. ( 6 ) Turns blue litmus paper t o red: 0.1N Na2C08, 0.1N AICL, 0 . l N NaCI. (6) Least soluble in water (18°C.): NaCI, (NH& SO,, BaSOd, CaCI.. I d ) Most soluble in a solution of NaOH: Cd(0HI.. (a)
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Highest atomic number: N, W, 0 , Re. (f) Largest number of planetary electrons: Na. S, C1. Al. (2) Calculate the formula weight of (NH4)2Cr20v. (3) Calculate the per cent. composition of Na2COs. (4) From a study of the solubility curve in your text estimate the solubility of: (a) KNO* a t 50°C.; (b) KC1 a t 30°C.; (c) K2Cr20,a t 70°C. (5) From the density value of NO show how to calculate its (e)
G.Y.W.
(6) Give the formula of the reagent that will dissolve. (a) Z ~ ( O H ) Z but , not Cd(OHh. (b) SnS*,but not SnS. (c) Ag, but not Pt. (d) BaCOa, but not BaSO&. (7) The following reagents only are available: Ba(OH).. &Cr201. FeS, Zn, P, CuSO,, HxO, HC1, NH40H, KI, S, I, HnS04. W"te equations showing how you would proceed to prepare: (a) lithopone; (b) cuprous iodide; (c) hydrogen iodide. (8) The following m&ls and solutions are available: Cd, Ag. N CdSOc N AgsS04. (a) Sketch a primary cell. (b) Calculate the voltage of the cell. (9) When 4.6 grams of the hydrate of sodium sulfate were heated to constant weight, 2.57 grams mere driven off as water vapor. Determine the formula of the hydrate. (10) In what part of the periodic table would you look for the elements having the characteristics indicated? ( a ) Form the most stable hydrides. (b) Form the most basic hydroxides. (c) Show the lowest degree of chemical activity.
Thus in Questions la and l b , the student discovers the usefulness of the Ionization Table in his text. In l c the Solubility Table, in 2, 3, and 9, the Atomic Weight Table, in 5 the Density Table, in 10 the Periodic Table, and 8 the Table of potentials come into use. Question 4 requires an understanding of the graphical representation of solubility. Therother questions may call into use the laboratory manual and the index of the text. Numerical problems are perhaps among the most easily adapted to the open-book form of test. 11. OPEX-BOOK LABORATORY EXAMINATION In this test the student may be permitted to use his own laboratory notes and to observe his own locker, chemical kit, and the supplied chemicals and equipment upon wh:ch the test is based. I t is not necessary to call attention to the waste of energy in grading laboratory notebooks. Why waste time and energy policing notewriting and why outlaw occasional quiet conferences of adjacent students when the results may be determined through tests based on student observations and records? If the notes fail to be useful to the student, certainly they are worthless to the instructor for class record, no matter how neatly and completely the notes may be written. I t is important to teach the laboratory student that he, like the true student of science, should record his observations specifically for his own
use. This does not mean that the instructor should ignore note-writing by his students; on the contrary, he should give the student the benefit of his experience in effective recording of observations. The notebooks should never be graded seriously. The laboratory open-book test should determine how well the student can use his notes in recalling exactly what he observed. If the student can be convinced that he will be examined thus, he will try seriously to record his observations in a manner most useful to himself and not for the instructor to grade. The points of view are distinctly different. A student with this more wholesome point of view is not so apt to be satisfied with beautiful paper reactions-he will want to see the chemicals in action. A first open-book test is usually necessary, however, to convince the average student that the instructor really means that he should write the laboratory notes for his own consumption. Unless the student is given a real urge to test for himself reactions which appear so easy in the textbook or on the lecture table, he will leave the course with a sadly distorted idea of this experimental science. A few typical questions will illustrate the form of test suggested above. (1) Determine the zero point of a balance that gave the followine resdines: 8.5 L. 5.6 R. 7.9 L. 5.0 R. 7.3 L. (2) Make a labeled sketch of a chareed drvinb " tube: (3) Make a sketch of a Bunsen flame. Ind~cateby a crass the hottest part of the flame. Cross-hatch the coolest part. (4) Describe in detail what you observed when you added concentrated sulfuric acid t o sucrose. (5) Manual, page 16. Und.erline the compound in each group which gave.aff oxygen most readily under the cabditions of the experiment: (a) mercuric oxide and manganese dioxide; (6) lead dioxide and potassium chlorate. (6) State the numbers and weights of your numbered metal strips. (7) From your experiments ??ith the following pairs of solutions state what you observed when (illustrate with chemical equations) (a) An excess of stannous chloride was added by drops to mercuric chloride; (b) Ammonium hydrovide was added in like manner to cupric chloride. (8) Under observations state what you heard, saw, and smelled.
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Substance
O O I N HCI 0 5 M NaCL 0 . I M Na.Sc01 Saturated solution SO* AmSs 0 2 M CrClr 0 2 M Narc08 0 . 2 M ZnCb 5 cc. 0 . I N AgNOa f I ce. 1 per cent. gelatin
Treatment
Observafionr
Drops of methyl violet "Chlorine wafer" 3 N HCI HsS Solution (NHM 3N NaOH excess 0 . 3 M AhISO04i Drops of 3 N NaOH 1 . 5 N NaBr
The complete and direct answers to these questions, as a rule, cannot be found in the textbook. The physically lazy student who has not performed the exper;ments thoughtfully quickly discovers the futility
of his usual technic. Close o b s e ~ a t i o nof the students a t work suggests questions which determine progress for student as well as for the instructor. 111.
PRACTICAL LABORATORY TEST
The student is provided with limited chemicals and apparatus with which to perform a short experiment, or is required to make a critical study of a definite "setup." The mechanical arrangement found quite workable is as follows: (a) the laboratory is divided into twenty-five numbered stations; (6) a t each station is arranged a typical "set-up" or a set of chemicals and apparatus; (c) a typed card is placed a t each station stating the purpose, procedure, and information sought; and (d) each student is provided with a sheet with twknty-five numbered spaces for statements concerning each experiment of corresponding number. Two or three minutes are allowed for each experiment, and a t a given signal the student moves to the next station in an orderly manner until the twenty-five experiments have been completed. The character of the test cited here can be illustrated by giving descriptions of several typical stations. The statements appearing in small type constitute the copy made available on the card to the student. (1) Summing up weights. weights.
Balance; crucible, and
(1) The balance has been adjusted to its zero point. the weight of the crucible.
Record
( 2 ) The flame. Burner. Mounted platinum wires, A and B. (2) Which wire, A or B, is in the hottest part of the flame?
(3)
Pieces of apparatus labeled A , B, C, and so forth.
(3) Name each piece of apparatus.
(4) Gas Laws. Inverted 200-cc. bottle mounted in filled sink or trough. (4)
Is the gas pressure in the bottle gretter or less than the barometric pressure?
(5) Gas laws "set-up."
Meter rule.
(5) The barometric pressure today is 768.7 mm. the pressure of the gas in the eudiometer?
(6)
Colored solution-(1) Mn04'; etc.
Cu+';
What is
(2) CrzOln; (3)
(6) The solution in each vial owes its color t o a well-known ion.
Identify each by number and formula of the ion.
(7) Odor test.
NHaOH, SOe, H2S, and so forth.
(7) Sniff cautiously. and formula.
Identify each substance by number
(8) Fifty-cc. graduated cylinder, 100-cc. beaker, narrow bottle with mark a t about 37-cc. level. (8) How much water will the bottle hold up t o the mark?
(9) A large scale temperature-vapor pressure curve mounted on card board. (9) According to weather bureau reports, barometric pressure on Mt. McKinley (elevation 20,300 ft.) is 415 mm.
What is the boiling point of distilled water a t that location?
(10) Test solutions: N Na2C03; N ZnCL Indicator: Methyl orange. Vials and droppers. (10) Unknown solutions may be N NalC08 or N ZnCb. Add one drop of methyl orange to a dropper of each test solution. Identify each by number and formula.
(11) Solubility of salts. Bottle of powdered gypsum and bottle of sodium chloride. Spatulas and testtubes. (11) Which salt is least soluble in water, A or B?
(12) Neutralization. Two burets, standard solutions of an acid and a base, indicators, and flask. (12) Before titation both burets A and B were filled to the zero mark. The volumes drawn off were required for neutralization. The acid in buret A, is 0.2N. Cslculate the normality of the base in B
(13) Successive tests. Test solution: HgN03. Reagents: ( a ) NaC1, (b) NH,OH. (13) To a dropper of the unknown add a dropper of reagent "a" and then a dropper of reagent "b." Record the formula of the ion indicated.
(14) Carbon dioxide apparatus. CuO and C in generator tube. Both tubes tightly stoppered. (14) The black mixture in the generator is CuO and C. The solution is lime water. Criticize this apparatus for preparing and testing CO*.
(15) Sulfur dioxide generator. End of safety tube above level of the liquid. (15)
Criticize this sulfur dioxide generator.
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Observations Lade on many students taking this form of practical test indicate that the manipulations required seem to help some students overcome that all too common acquired ailment, the "examination fear." The author in some instances has found that students who fared poorly in the usual closed-book examination conquer their fears and do creditable work in the practical test. Glaring examples of the reverse order are not uncommon. Perhaps we can ponder what one student said as he handed in his practical test paper, "I feel that the answers in this paper are definitely my own." In conclusion we must be mindful of the fact that the open-book or the practical laboratory form of test cannot be considered a complete testing procedure. In fact, it is very doubtful that any form of testing whether under the heading of the so-called "new type" or "old type" can be considered adequate. A large percentage of the good students will excel in any form of test but owing to some of the obvious evils of our systems of examining and grading many "good or "fair" students fail to become rated in proportion to their actual capabilities. As long as grades are required we should in fairness to the variations in student temperament use various types of tests for each distinct purpose; we should always strive to make the test a part of the teaching process
