AN EXPERIMENT IN PREDICTING PERFORMANCE IN GENERAL CHEMISTRY MAUDEB. SCOPIELD, SYRACUSE U~R~IT SYRACUSE, Y, NEW YORK Every year large groups of freshmen with widely varying abilities are required to take chemistry in our universities. The problem of recognizing these varying abilities a t the beginning of the course is a live one and administrators are becoming more and more conscious of the responsibility which it involves. Attempts to solve it by use of the experimental method have been the subject of a number of articles in
THISJOURNAL. The students in general chemistry at Syracuse University are divided into two groups: those who have studied chemistry before and those who have not. This paper deals with the former group which normauy numbers two hundred. I n September, 1925, a few simple preliminary chemical tests were given in an &ort to section the class on the basis of ability. The results of these tests indicated that the high-school preparation of our students in chemistry and the time which elapses after the preliminary course varies so widely that any chemistry examination may prove to be only a memory test. For sectioning purposes, we are concerned more with what students can do in college chemistry than with what they may have remembered. In September, 1926, we again devised a placement examination. This time the tests were based upon the assumption that success in the general course will be determined by the following factors: (1) whether the student pays attention; (2) whether he is inclined to follow directions -this applies to laboratory work or any other assignment; (3) whether, given a few facts, he can reason logically and consistently, or given a general rule, can he apply it to a specific case; (4) whether he can perform simple arithmetical processes which involve the placing of the decimal point; (5) whether he can work problems which involve the use of direct and inverse proportion as well as exercise "arithmetical common sense" in handling percentage problems. The tests we devised to measure the inclination to pay attention and to follow directions did not give satisfactory results. But the outcome of the tests on the last three points was interesting. Following is the examination : Part 1 (5 Credits) 1. What is one and six-hundredths per cent of five-hundred-sixty? 2. Express nine-hundred-seventy-fiveten-thousandths as per cent. 3. Multiply eleven and eleven-hundredths by five-thousandths. 4. Divide six and six-tenthsby twenty-two-thousandths' 5. Subtract five and fifty-two-thousandths from ten and four-hundred-fifty-fivethousandths.
Read the notes before trying to answer any questions in Part 11. Then answer questions in the order given. Place answers opposite questions. Use hack of question paper if scrap paper is desired.
Notes Here is listed a part of the electrochemical series of the metals, giving names and symbols. 1. Potassium, K 2. Sodium, Na 3. Barium, Ba 4. Strontium, Sr 5. Calcium, Ca 6. Magnesium, Mg
7. Aluminum, A1 8. Manganese, Mn 9. Zinc, Zn 10. Chromium, Cr 11. Cadmium, Cd 12. Iron, Fe
13. Cobalt, Co 14. Nickel, Ni 15. Tin, Sn 16. Lead, Pb 17. Hydrogen, (H) 18. Copper. Cu
19. Bismuth, Bi 20. Antimony, Sb
21. 22. 23. 24.
Mercury. Hg Silver, Ag Platinum, P t Gold, An
The activity of the metals decreases in the order given by the eledrochemical series of the metals. That is, potassium is the most active and forms compounds which are the most stable while gold is least active and forms compounds which are most easily decomposed. All metals which stand above (H) ~. in the series can replaceit. Any metal in the-series can replace all others below it in a compound. (Example: Zn CuS04+ ZnSO. Cu, or simply, zinc replaces copper.) The chlorides of all the metals of the above series are soluble in water except PbCL, AgCl, HgCI. All the nitrates of the series are soluble in water. All the sulfates of the series are soluble in water except BaSOb SrSO,, PbSO.. Most fluorides of the series are insoluble in water but the fluorides of K, Na, NHI, Cu, Ag are soluble. All fluorides are soluble in dilute acid. HgO and A g ~ 0lose all their oxygen a t 1000'. CuO will losepone of its oxygen while BisOs and Sb203lose part of their oxygen a t that temperature. The maximum temperature available from the Bunseu burner is approximately
+
+
low'. Zinc melts a t 419" C. (C. indicates Centigrade degrees). Zinc bails a t 918' C. Zinc oxide and mercury oxide will not melt or boil below 15W" C. Mercurymelts a t -38' C. and boils a t 357' C. Silver melts a t 961" C. and boils a t 1955' C. ' C. and bails a t 100' C. Watu. melts a t 0
Part II (40 Credits) 1. Will zinc replace hydrogen? 2. Will mercury replace hydrogen? 3. Will copper replace zinc? 4. Will copper replace silver? 5. Will antimony replace hydrogen? Observing the following conventions as to physical states of matter, (1) A line under the formula if a solid or insoluble substance. E x a m p l e g . (2) A line above the formula if a gas. Example Hn. (3) Formula only if a liquid. Example 8 0 . (4) (aq) placed after the formula if a solution. Example NaCl ( a d , you are to indicate the physical state of each substance under the conditions given in the following equations which are balanced and otherwise correctly written. NaCl NaNOa AgCl (AU four substances are in water). 6. AgNOa K&Ol --+ BaSOl 2KC1 (all four substances are in water). 7. BaCll
+ +
-+
+
+
+ +
On -+2ZnO (all a t a temperature of 1100' C). 9. 2HgO heat --f 2Hg On (all a t a temperature of 1100' C). 10. Which metal oxides of the electrochemical series would lose all of their oxygen a t the temperature of the Bunsen burner? 11. Fill in the chart indicating whether the following substances will be solid, liquid or gaseous a t the temperature indicated: Example: water a t 1500" C. is a gas. 8. 2Zn
+
-lo0 C.
Water Mercury Silver
20° C.
15W°C.
I
I
Gas
I
I
12. Sodium hydroxide and silica react together to form sodium silicate which is commercially known as water glass. Sodium hydroxide does not react with carbon. perMelted sodium hvdroaide attacks phtinum. Porcelain crucibles contain a large centage of silica and graphite crucibles are chiefly carbon. Crucibles are also made of a solid stick of sodium hyiron. nickel.. ~latinum. and other metals. If vou were given . . droxide and a choice of a graphite, porcelain, and platinum crucible, which would you select in which to melt the sodium hydroxide? 13. If you were given a solution which contained sodium fluoride and hydrochloric add, haw muld you prepare an insoluble fluoride?
Part III (5 Credits) 1. Charles' law states that if the pressure is kept constant, the volume of a gas varies directly as the absolute temperature. (The absolute temperature is 273" higher than the Centigrade temperature. Example: 20' C. is 293- absolute.) If a certain amount of gas occupies a volume of 6.6 cubic centimeters a t 57' C., what volume will i t occupy a t 27' C.? 2. Boyle's law states that if the temperature is kept fixed but the pressure varied that the volume of a gas will vary inversely as the pressure applied. If a certain gas occupies 40.4 cubic centimeters a t 5 atmospheres pressure, what volume will it occupy a t 8.08 atmospheres? 3. A sample of zinc ore was found by analysis to be 90.2Y0 zinc sulfide, how many pounds of zinc sulfide could be obtained from 1.06 tons of the ore? 4. Calcium carbonate is 40y0 calcium. How many grams of calcium carbonate could be obtained from 16.648 grams of calcium? 5. Sulfuric acid is 32.6% sulfur; pure zinc sulfide is 32.8% sulfur. But the zinc sulfide ore available is only 90.2%pure. How many tons of sulfuric acid could be prepared from ten tons of the zinc sulfide ore?
The class was allowed fifty minutes to answer this examination. Section I11 contained more problems than the best students could complete in the allowed time and was placed last for a two-fold reason: we wanted no one t o finish the examination and we wanted each one to answer Sections I and I1 to the limit of his ability. For this reason, Section I11 was partially a speed test; undoubtedly the average grade would have been higher had more time been allowed. The letter grades of this examination were given by assigning the highest ten per cent A; the next fifteen, B; the next fifty, C ; the next fifteen, D; and the lowest ten per cent F.
The semester grade is the composite of: laboratory, one-fourth; monthly and final examinations, one-fourth; and daily recitations, one-half. The recitation grade is based on ten-minute written quizzes given a t every class meeting. The letter-grade distribution for the semester endimg January, 1927, was: 7.8% A, 18% B, 45.3% C, 13.4% D, 15.2%F. The letter grade distribution for the semester ending June, 1927, was: 10.4v0A, 21.8% BB,30% C, 26% D, 11.4% F.
Lettergrade of the placement elamination given Scpt.. 1926
A
Semester grade in chemistry 1st semester-January, 1927
2A
8B
9C
2D
No.of
students
OF
21 31 108 36 17
213 Did not register
Semester grade in chemistry 2nd remerte-June, 1827
2nd semester
A B C D F
3 5
7 1 0
3A 5A 7A 1A OA
8B
4B 25B 2B OB
5C 6C 30C 10C 2C
2D 8D 20D 5D 3D
OF 2F 11F 2P
4F
Failed 1st sem.
NO.of students
0 1 8 15 8
21 31 108 36 17
213
Table I shows the relation between the grades on the above examination and the grades in chemistry for each semester. These conclusions may be drawn from the table: (1) Of the 52 who were in the top quarter in the placement examination in September, only one failed the course in January and two more failed in June; i. e., only three people or 5% of this group failed during the year. (2) Of the 53 who were in the lowest quarter in the September placement examination, 23 failed in January and 6 more failed in June, or 55% of this group failed during the year. In this same group, no one made an A the first semester and only one made A the second semester; i. e., only 1.8% of this group made A during the year. (3) 66% of the A's in the course in January came from the group which constituted the middle fifty per cent in the September placement examination. In the light of these conclusions, we would have been justified in placing
those students who were in the lowest quarter in the September examinations in poor sections. This examination would have been a fair test to sift out the F students, although i t would not have located the A students of the course. We sought the relation between high-school grades and grades in college chemistry by comparing separately the high-school grades in (a) chemistry, (b) elementary algebra, (6) intermediate algebra, (d) plane geometry, (e) solid geometry, (f) trigonometry with the semester grade in chemistry for each individual student. Most of the high-school grades were from New York State Regents' examinations, which have a passing grade of 65. We found that, in general, those students who rated below 80% in any of the above subjects did distinctly poorer work in chemistry than those above 80%. However, as an individual student may have made more than 80% in one of these subjects and less than 80% in another, some of the results were conflicting. COR~BLATION BETWEEN HIGHSCHOOL GRADESIN CWMSTRY1WD AND
MATBEMATICS
COLLEGE GRADES IN CHEMISTRY Semester grade in chemistry 1st semerte-January, 1927
AU "High" Chem. "High" Part of Math.
No. of
students
9A
8B
7C
2D
OF
26
3A
10B
21C
5D
6F
45
3A
11B
35C
9D
3F
61
1A
4B
17C
11D
19F
"High" "Medium" Chem. "Low" Part of Math. "High"
All "Low"
52
184
Didnot register 2nd semester
AU "High"
4
( Chem. "Hi~h" Part of ~ a t h .3
I[
.
Failed 1st sem- No. of ester students
semester grade in chemistry 2 n d s e m e r t e ~ J u n e 1927 .
8A
6B
5C
3D
OF
0
26
4A
15B
12C
4D
1F
6
45
2A
9B
17C
15D
8F
3
61
2A
2B
10C
11D
6F
19
52
"High"
"Medium"
Chem. "Low" Part of Math. 7
"High"
All "Low"
2
VOL. 4, No. 9 EXPERIMENT IN PREDICTING PERPOWNW IN GENERAL CHEMISTRY 1173
Next we sought correlation between all of the high-school grades in mathematics and chemistry and the semester grade in chemistry. The results are recorded in Table 11. All "High"-Those who rated 80% or higher in high-school chemistry and in all of the mathematics courses presented for entrance credit. Chemistry "High" and part of mathematics "Highu-Those who made 80y0 or higher in high-school chemistry and who made SOY0 or higher in one or more courses in mathematics presented for entrance. Chemistry "Low" and part of mathematics "High"-Those who made below 80y0 in high-school chemistry but 80% or higher in one or more courses in mathematics presented for entrance. All "Loww-Those who made less than 80% in high-school chemistry and in all of mathematics courses presented for entrance. Table11 shows the relation between the grades of these four groups in high-school work and the grades in college chemistry for each semester. Certain conclusions may be drawn from this table: 1. Of the 26 who were all "High," not one failed either of the semesters. Approximately one-third of this group made A in January. Approximately one-third of this group made A in June. From this group came 50% of the A's made in the course in January. From this group came 42y0 of the A's made in the course in June.
COERELATION BETWEEN
TABLEI11 HIGH-SCHOOL AND COLLEGE GRADES IN CHEMISTRY
Claosified a. to grade in high-school eheplirtry (math. not eonudered)
"High" in high-school chem14A istry (80 or above) "Low" in high-school chemistry (below 80) 4A
No. of
Semester grade in chemistry 1st s e m e s t e ~ J ~ a n u a r1927 y,
.tudentll
20B
37C
8D
8F
3 drop
90
18B
60C
21D
21F
4 drop
128 218
Did not mgkter 2nd semester
"High" in high-schaol chemistry (80 or above) 10 "Low" in high-school 13 chemistry (below 80)
Semester grade in ehemistrg 2nd seme$fer-June, 1927.
13A
24B
25C
8D
4A
14B
30C
30D
Failed 1st se- NO.of mestel atvdents'
2. Of the 52 who were all "Low," only one made A in January and two made A in June. Of the 52, 19 failed in January and 6 more in June; i. e., 48y0 of this group failed either in January or in June. 60% of the
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S E F T E ~ E1927 R,
F's of the course in January came from this group. 28% of the F's of the course in June came from this group. 3. Taking the other two groups of this classification, the January results do not indicate much difference between the " H i g h in highschool chemistry and the "Low," but the June results show that those who were "High" in high-school chemistry have done definitely better. This classification from high-school grades would have served fairly well t o predict the success in college chemistry. Conclusion 3 raised the question as to the value of classifying the entering students as "High" in high-school chemistry (80 or above) and "Low" in high-school chemistry (less than 80). This question is answered in Table 111. From Table I11 may be drawn these conclusions: 1. 15% of the group which was "High" in high-school chemistry made A in January. The same per cent made A in June. 11% of this group flunked either the first or second semester. 77% of the A's of the course in January came from this group. 68% of the A's of the course in June came from this group. 24% of the F's of the course came from this group in January. 9% of the F's of the course came from this group in June. 2. Of the group which was "Low" in high-school chemistry, 3% made A in January and 3% made A in June. 28% of this group made F during the year. 63% of the F's of the course in January came from this group. 76% of the F's of the course in June came from this group. The results in Table I and Table I1 suggest a program which we plan to follow in sectioning in September, 1927. From the entrance grades in high-school chemistry and mathematics, those students who w ill take the general chemistry course will be classified under the three headings: All "High," All "Low," "Medium." The "Medium" group will then include all those who were neither above 80% in all of the high-school subjects considered nor were they below 80% in all. This classification can he completed before registration and the "High" group placed in good sections and the "Low" group in poor sections as they register. At the first lecture session, a placement examination will be given, the results of which will probably warrant a few additional changes. The results of 1926 indicate it would have been wise t o shift out of the poor section those who were in the top quarter in the Septemher placement examination and t o shift out of the good sections into poor ones all who were in the lowest quarter. The "Medium" group will always include potentially good students. But any of this "Medium" group, who rate in the lowest quarter in the September examination, should be placed in poor sections. Had we followed the program outlined last September, we would have originally placed in poor sections 70% of the students who finally failed the first semester's work. With the
exception of one student, we would have placed our A students in good sections or in medium ones-which are potentially good ones. It is of interest to note that of the group which was "Low" in high-school chemistry and in all of the mathematics courses, 22 were also in the lowest quarter in the September examination. Of the 22, 16 failed first semester and 2 more the second semester. The results of Table I and I11 suggest another program for sectioning. All who made 80yo or more in high-school chemistry might be classified as "High" in chemistry and registered in good sections; those who made less than 80% in high-school chemistry as "Low" in chemistry and registered in poor sections. At the first lecture session, a placement examination should be given as a basis for such shifts as seem warranted before assigning lockers. From the "Low" group, those students who were in the lowest quarter in the September examination should he assigned to poor sections. I n the same section should be placed any who were " H i g h in high-school chemistry but were also in the lowest quarter in the September examination. Had we followed this plan in September, 1926, we would have placed in the poor sections GOYo of the F's of the course for the first semester. There were 52 such people and the first semester record of the 52 is: 0 A, 4 B, 19 C, 7 D, 20 F and 2 drops. The latter method of sectioning requires less information concerning the high-school records of individual students and evidently serves fairly well in prediction. By the former method, we could have grouped most of the flunkers in one section and about half of the A students together in another section. By such sectioning, it is possible t o cater t o the special needs of each group without being unfair to either the good or the poor student. We can see no reason why this method of sectioning could not be extended to a group which had never had chemistry. Grades in highschool mathematics serve as a fairly good means of predicting of success in college chemistry. As students who do not present chemistry for entrance usually do present physics, the high-school grade in physics ought to be of value. We are working on those data a t the present time. The group could be first classified by their high-school grades in physics and mathematics. A modified placement examination could be given them a t the first lecture session as an early indication of the adaptability of these students to a "chemical environment." We are preparing another placement test for this fall which will be of the same nature as the one of last year but which will include more questions. We are also preparing a test for the group which has never had chemistry. I wish to express my appreciation t o Dr. R. A. Baker for his interest and advice in the gathering of the data and the preparation of this paper.
