Donald C. Gregg
University of Vermont Burlington
Asking Students To Use Facts
For, the first decade of his career as a teacher, the author used a method of presentation that was essentially informative. He featured the descriptive fact and predeveloped idea, often at the expense of a thorough discussion of the basic concept. Occasionally he asked his students to use facts, but more often he expected only that his students remember them. His approach to numerical problems was based on the mastery of certain generalized types. During this period, the enjoyment gained from the classroom seemed ample, but during his second decade of service the author has uncovered a greater and more invigorating enthusiasm by using a differentapproach. He presents that approach here because he believes that all teachers are seeking a method of teaching which is genuinely more satisfying. He believes that all will he interested in a specific teacher's current personal doctrine. Although the approach is not new, it bas particular merit because of its gradual evolution over the years, influenced strongly by many contacts with teachers and students. The current pattern is designed to help the student to evaluate, digest, and use a selected body of chemical facts and concepts. Its major intent is to use chemistry as a means of enticing students to thmk and reason logically. Stress is placed on the application of facts, and especially on an understanding of the ways in which valid concepts may be applied to the solution of original problems. So-called descriptive chemistry, which provides the facts, cannot be neglected completely, but most of the class time is devoted to explanation and interpretation. In this way it is hoped that those students who forget the descriptive aspects of their chemistry course will a t least retain the mental attitudes that they have learned to use there. Indeed, it is probable that the intellectural exercise which they have gained in such a course is more valuable to them than a cursory knowledge of the subject matter. Conversations with former students seem to verify this. As taught to an introductory class of not less than 300 students, this approach appears to be different from any that many of them have encountered previously. As a consequence, their attitudes and grades cover a Based on a paper read at the 22nd h n u d Summer Conference of the New England Assaeiation of Chemistry Teachers in Orono, Maine, August, 1960.
478
/
Journal o f Chemical Education
wide spectrum. Those who both expect and want to be educated realize that the use of facts and ideas in chemistry is a pleasant, stimulating experience. Those who expect and want only to be trained to follow specific procedures, and to be told just what to memorize and repeat, are usually quite disappointed. Fortunately, many of these latter finally change their points of view when they realize that their knowledge is more valuable once they have learned how to use it. Examinations Are the Key
The grades earned in writing different kinds of examinations seem to indicate that most college students are able to learn facts and ideas: they are willing to memorize almost any reasonable amount of material. However, many of them lack the ability to use the facts and ideas so memorized. I t is the author's contention that one of the major purposes of an examination is to determine proper rewards for the students who justly deserve them. If the examination tests primarily the student's ability to gather and to remember, rather than his ability to understand and interpret, the result is a meaningless assignment of rewards. Because the student,~are in college, their willingness and ahility to memorize have already been demonstrated. Their very presence in class is, in a sense, a reward for having attained this willingness and ability. It would appear that in an intellectual environment, examinations which test primarily the student's ability to use facts would lead to a more equitable assignment of merit. Nevertheless, when this is done the result is a grade which is generally much lower than that to which the student is accustomed. For example, the first hour examination of this kind, given each autumn, always yields a low median grade, usually between 50 and 55. It is significant that for the past seven years, the grades on this initial test have varied from 100 to 0, inclusive. Although subsequent examinations always produce several papers with scores below 20, t,he median grades are invariably higher. The median scores of the later examinations usually remain essentially constant. There are certain types of questions and numerical problems which have been found useful in persuading the students to understand how specific laws and conrepts can he applied. These are used almost exclusively; there are practically no questions on any
examination used during the year which can be answered by simple recall. For example, no dehitions are ever requested. On the first hour test one aut,nmn the students were asked What is the atomic weight of Z if exactly 0.1 mole of X5and 40 g of Z2 react oompletely to yield XsZ4as the sole product?
Only 35 out of 345 students reported the correct answer although all had been warned that they were expected to know how to use atomic weights and interpret quantitative data. One disturbing aspect of this event was the fact that prior to taking the author's course over 200 members of the class had allegedly mastered what most of them called "weight-weight" problems; many of these students were disturbed to learn that their understanding of atomic weights and chemical equations had been incomplete. Others were more disturbed by what they called the "trick" question. I t is easy, for example, to determine which students understand the significance of atomic weights and chemical formulas by asking questions such as Haw many grams of mercury(I1) oxide, HgO, must be decomposed to yield half as many atoms as there are in 140 g of argon?
A Kovember hour examination contained
tions. The aut,hor tries continually throughout the year to correct this tendency by pleading for strict interpretation of data and adherence to directions, and by including on each test a t least four or five major questions and problems that require careful inspection of the printed word. Many of these are based on 100200 word expositions either of situations or of specific physical and chemical phenomena. The questions and problems can be answered or solved, only by using the data given. Usually these data are facts unknown to the class prior to the test. The students are told to read carefully to find the key words in the statements, these words being either identical with or similar to those used in expressing some well-known law or concept. The application of the proper concept to the problem a t hand then follows logically. An October hour test presented If the density of molybdenum is 10.2 g/ml, and that of duminum is 2.7 g/ml, how many grams of molybdenum occupy the same volume as 81 g of aluminum?
S i t y per cent of the students in a class of 320 reported an erroneous value, although all had heard much about density in class and laboratory. A November test contained a 195-word "story" about a situation regarding three reagent bottles. One of the statements within this exposition was
Two-tenths of a gram of a gas occupies 100 ml a t -1E6.5'C and 760 mm of Hg. What is the mass of one mole of the gas a t 1520 mm of Hg and ODC?
A tightly stoppered glass bottle A of 150-ml capacity contains 60 ml of liquid acetone. . . . What volume, in milliliters, inside bottle A is occupied by the suhstance acetone?
Xearly half the students who first obtained the mass of one mole then proceeded to "correct" the mass to that at 1520 mm. Robert Boyle must have turned over in his grave. Two recent mid-year tests contained uonc of the conventional chemical symbols and names, either of elements or compounds. There were no atomic weights printed on the examination paper although each student did have a conventional periodic chart. Nevertheless, all the concepts that were "covered" on the semester hour tests were included in some way on these mid-year examinations. One section of one of these included
At least 150 students in a class of 350 concluded that the acetone occupied only 60 ml. On a mid-year examination was
Singly positive ions of element E M were present in the clectrolyte of an electrolytic cell. The passage of 19,300 coulomhs of electricity through the cell yielded 17.10 g of elemental EM. What is the atomic weight of E M ? At which electrode did the EM appear? Haw many extranuclear electrons are in the uncharged atoms of EM?
Many students said that no definite statement could be made, obviously overlooking the fact that the solution was aqueous and that oxonium and hydroxyl ions were definitely present. A sizable group stated that copper(I1) ions might be present, neglecting the fact they were asked which ions were definitely present. Others said that some ions of Group I were definitely present, failing to realize they were asked to idrntify each ion.
A problem that appeared on a final examination lyas A n ionic compound A consists only of potassium ions and those of the conjugate base of a monoprotic molecule named psychic acid. If 50 g of A is added to water to yield 500 ml. of solution, the pH of the solution is 9.5 and the potassium ion concentration is 0.91 M. (At. wt. of K is 39.) If 18 g of psychic acid is added to pure water t o yield 2.5 liters of solution, is the axoniom (hydronium) ion eoncentrittion equal to, less than, or greater than 0.1 A{?
Approximately one-third of a class of 250 failed to realize that the fact implied definitely that psychic acid was a weak acid. For many more the molecular weight of the acid was particularly elusive. One of the major stumbling blocks for many students seems to be a tendency to read carelessly, thereby failing to use correctly t,he facts presented in the ques-
A sample of water is boiling briskly. What positive, correct statement can be made about the vapor pressure of the water?
I n a group of 350 students, a t least 175 blithely assumed, much to their subsequent chagrin, that the water was in an open vessel. An April hour test presented .4 student was given a clear blue aqueous solution D. Addition of dilute HC1 to D yielded 8. white precipitate. Identify ~tschion that was definitely present in D.
On a November test was What msss of gaseous methane (mol. wt., 16) a t 0.5 a t m and 100°K contains the same number of molecules as 8.5 g of gaseous ammonia (mol. wt., 17) a t 1 atm and O"C?
Xearly half the students in a class of 350 failed to recognize that equimolar amounts (0.5 mole) of the two gases would contain the same number of molecules. Because the problem appeared to he an Avogadro's Law problem, many became hopelessly lost while computing the volumes of the gases. These students were shaken when they finally realized that only Volume 38, Number 9. September 1961
/
479
two very simple divisions were needed. While the organization of the course and its syllabus are important factors in determining the depth and breadth of a student's work, it is the examination program which best sets the pattern for his intellectual development. If he is rewarded most for his ability to memorize and reproduce from memory, this is the aspect of his study which will receive the greatest at-
480
/
Journal of Chemical Educofion
tention. If he is required continually to use facts and develop his own ideas on examinations, his attitude toward the course and toward studying f o r t h e course will be oriented in quite a different way. Good examinations teach the student as well as inform the instructor. Interestingly enough, questions which ask the students to use facts perform both of these functions better than any other kind.
