VOL. 8, Nos. 7 AND 8
TESTING LABORATORY TECHNIC
1321
TESTING LABORATORY TECHNIC IN HIGH-SCHOOL CHEMISTRY
The present study was planned and set up in an attempt to measure the achievement of high-school chemistry students in laboratory technic. This made it necessary to build an objective test for, a t present, the achievement tests are almost entirely concerned with the text content of the course of study. Several questions were considered in laying out the work. What does the present program of laboratory work in chemistry contribute to the achievement in chemistry? To what extent is the achievement in the laboratory phase of chemistry comparable to the achievement in the classroom work? It was hoped that data secured in making a study of this kind might he valuable in working out a more accurate means of evaluating the work of the student. The method of study followed in this investigation may be briefly outlined as follows. A test was constructed and administered to students who had completed one year's work in high-school chemistry. The test consisted of items selected from the laboratory work, usually included in a high-school course of study. The test was given by the instructor during a regular class period. The papers were then corrected from a key by each instructor, who tabulated the results and returned them to the writer. The Test The work of constructing a test presented some difficulties. In order to measure and evaluate the results of laboratory practice, it seemed best to build a test that would most nearly reproduce the situations which the students have experienced in actual laboratory practice. To do this, the test items were written in the form of problems, each illustrated with a drawing which would represent the conditions discussed in the problem, or show the difficulty encountered. The initial test consisted of ten or twelve items mimeographed and used in the writer's classes. The results were then tabulated and used in preparing a revised form, which was used in 1926 in testing about 200 stndents. On the basis of the results now available a more extensive test was constructed. This form, used in 1927, was given to 535 students, representing ten high schools. The final form of the test was constructed for use in the spring semester of 1928. The test in two forms consisted of 80 items each. The two forms were essentially alike, the problems used involving the same principles but applied through different material. This form required about 40 minutes to administer although a few students found some difficulty in completing the test in that time.
The selection of material, representative of a typical course in laboratory chemistry, was one of the major problems. I n order that the material used would be representative of a fair sampling, all available laboratory manuals were consulted. I n the final checking, all items were rejected which were not treated in all the manuals. A summary of the source materials is as follows: 1. Laboratory Manuals: a careful study was made selecting materialcommon toall. 2. The College Entrance Ezaminalion Board: " A Proposed Definition of HighSchool Chemistry." 3. American Chemicd Sociely: " A Standard Minimum High-School Course in Chemistry." 4 . Teacher Suggestions: problems involving principles and practices. 5. CampJetim oj Apparatus: problems in completing various types of apparatus. 6. Courses o j Study. 7 . Dificzrlties: a group of problems selected from the incorrectly set up apparatus which is found in high-school laboratory work.
The test, as mentioned above, was prepared in mimeographed form. The drawings were prepared with as much accuracy as is possible in a mimeographed reproduction and served the purpose very well. The extended use of illustrations prevents the printing of the entire test in this report, but a few typical questions will serve t o illustrate the type of problem and show the general mechanics of the test. These sample test questions are given below. The extent t o which the test covered the laboratory phase of the highschool course in chemistry may be estimated by considering the analysis of the test which follows. A summary of the facts included in the problems shows the following content. 1 . Filtering: recognition of "filtrate" and "precipitate." 2. Flames: a study of flame structure (hottest part, oxidizing flame, reducing flame). 3. Apparatus: a. Completion Type: problems involving the completion of apparatus used in the preparation of ammonia, sulfur dioxide, testing for carbon dioxide, etc. b. Incorrectly Assembled Types: problems in checking types met with frequently and including unsealed thistle tubes, submerged delivery tubes, burners when not necessary. 4 . Borez Beads: a. IdentEcation of beads containing typical salts. b. Beads prepared in reducing flame instead of oxidizing flame. 5. Eledromotive Series of Mekzls: problems of metallic displacement and the nature of the ions in the resulting solutions. 6. Distillalia: study of the process and applications. 7. Conductivity: identification of electrolytes and the polarity of the electrodes. 8. Electrolysis: water, sodium chloride solution, and potassium chloride solution. 9. Principbs of Gar Collection: problems involving density, solubility, and chemical activity with water.
VOL. 6, NOS. 7 AND 8
TESTING L A B O U T ~TECHNIC ~Y
1323
10. Drying Gases: problems involving the use of several drying agents with various gases. I . Reduction end Oridation Reactions. 12. Classification of Apparatus: adaptability of certain types of apparatus for the preparation and collection of a given substance.
Test Questions 1. A student workimg in the laboratory read the following directions. "Filter the mixture and add ammonium hydroxide t o the filtrate." The drawing in Figure 1 shows the filtering process. Indi- ---~ a t ethe filtrate by writing the word, "Filtrate," on the - - proper dotted line extending from the drawing. 4. The drawing in Figure 3 represents a part of the apparatus required for the laboratory preparation and col-lection of ammonia gas. The apparatus, which contains the ~ ~ as vou will notice, does not contain a de. r .o u ematerials. -- livery tube. You will complete the apparatus by drawing a delivery tube in Figure 3, extending from the point X t o FIGURE1 the proper bottle for the collection of the ammonia gas. 7. The properties of ammonia which make its collection necessary as indicated in the drawing in Figure 3 are:
---m -1
a ................
FIG^ 3 the generator, What was wrong? Study the problem carefully. Gas was not collected in bottle B because. ................. . . .
6 ................ 44. I t is not unusual t o encounter certain difficulties in laboratory work. A student was trying to prepare hydrogen as shown in Figure 12, but after working for some time was unable to collect any hydrogen though a vigorous re=tion seemed t o be taking place in
-9
'--
63. The illustration in Figure 17 shows apparatus which may be used in the electrolysis of a solution of sodium chloride. I n "Tube A,". ............. will collect, while. .................. .will collect in "Tube B." 64. The electrolysis of brine, as shown in F i r e 17, is continued until the sodium chloride is entirely decomposed. The solution remaining in dish C will then contain.
.......
6.5. The apparatus in Figure 17 may he used for electrolysis of water by acidifying the water with sulfuric acid. The gas collecting in "Tube A" will be.. . . . . . . . a n d that collecting in "Tube B" will be. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .
.
Coijperating Schools The tests have been given to several thousand students. Prom this testing program, data are available for 1726 students. More than twentythree schools have cooperated in giving the tests although, a t present, the results are available for only twenty-three.' The results represent the work of a considerably larger number of teachers since, in quite a few instances, several teachers are represented in the report of a given school. The schools represent a good geographical distribution and should represent a fair sampling of students. Results A brief statistical summary of the results are given in the table. These data are not offered in support of any conclusions to be suggested later. They are interesting however in showing the similarity of the two experimental forms of this test. The values given have been calculated from the total results of the testing program with the exception of the correlation coefficient which is based upon the scores of two schools. The two schools selected for calculation of the correlation coefficient are average schools located in different states, one being a county high
1927
Number of students tested Mean, arith. Standard deviation DELAwARB: Wilmington, Tower Hill High MASSACHUSETTS: Boston, English High Melford, Melford High MICRIGAN: Ann Arbor, Senior High
NEBRASKA: Omaha. Technical High NEWJERSEY: Atlantic City, Public High Morristown. Momstown Hixh Onto: Akron, West Hixh ~ a r b e k o n cent& , High Canton. McKinley High
497 51.35*0.293 9.7*0.21
Berm A
1928
648 46.6*1.2 10.10+0.28
Pmm B
547 42.7*1.4 11.0*0.33
Cleveland, East High Cleveland, Glenville High Cleveland, West High Cleveland, Western Reserve Univ. (Summer) Cleveland Heights, Heights High Lorain, Lorain High Salem, Salem High Wadsworth, Wadsworth High Warren, Harding High Youngstown, South High WASHINGTON: Tacoma, Stadium High WEST VIKGINIA: Wayne. Wayne County High Wheeling, Wheeling High
VOL.6. NOS.7 AND 8
TESTING LABORATORY TECHNIC
1325
school and the other a small city high school. The reason for selection of these two schools is that the reports were more complete than the others. TABLEI1 COEB~CIENT OF RELIABILITY BETWEEN TESTSA City A City B
34 cases
73 cases
AND
B
0.881 0.887
The reliability coeffiaent was determined by means of the formula: I = -
=Y 4.zx2.zy9
This is the calculation of the coefficient of reliability in terms of the deviations from the means. The results obtained in making these tests furnish interesting data, as they suggest some rather definite tendencies of students in the interpretation of problems involving the use of laboratory apparatus. Conclusions established on the basis of the data now available may be considered premature. The data can be used to better advantage in continuing the investigation of the measurement of results of laboratory practice. There are several reasons why the results can be considered as of only tentative value. In the first place, the tests are new, involving a kind of work with which the student was not familiar. From this angle, i t may have taken him somewhat by surprise. Then, too, the data may indicate the difficulty of the test item as well as showing the achievement of the student. The first factor, the new type of test, makes it more difficult to interpret the results. Some work has been done in checking the achievement of students in laboratory work in high-school chemistry, but this work has been largely from a somewhat different approach.% It may be assumed that any results obtained in making a study of this kind will serve best in stimulating further research as cnrriculum reconstruction proceeds. The results of laboratory practice in chemistry should yield to accurate objective measurement. Such measurement will have to be made before a final definition of the laboratory phase can be made in our new curriculum. A brief summary of the results of testing more than 1700 students is presented here in order that one may more easily study the situation. Webb, H. A., "A Test of Laboratory Resourcefulness," Sch. Sci. & Math., 27, 457-65 (1927). Smith, H. A,, "Achievement of Pupils in Laboratory Instruction," THISJOURNAL, 3, 307-13 (Mch., 1926). Horton, R. E., "Improvement of Scientific Ability through the Use of the Individual Laboratory Exercise in Chemistry," Ibid., 6,1130 (June. 1929). Horton, R. E.,"Measurable Outcomes of Individual Laboratory Work in High-School Chemistry," Contribution to Education 303, Teachers' College, Columbia University, New York City.
The analysis is submitted i n t h e f o r m of a s u m m a r y of f a c t s rather than by reference to the various questions since the entire test is n o t reproduced. These results show the total number of students tested, the number of correct answers, and the percentage of correct answers on the following facts tested. Paeto tested
Recognition of "filtrate" in a filtering process.. . . . . . . . . . . . Locate the "oxidizing flame" of a Bunsen burner.. . . . . . . . . h t e the "reducina.flame" of a Bunsen burner.. . . . . . . . . Complete apparatus for preparation of NHz. Draw a deliverv tube from generator to bottle. .................. Know -the properties of ammonia which determine the method of collecting the gas.. ........................ Complete apparatus for making a chemical test for carbon dioxide. ............................................ Know that hydrogen chloride gas cannot be collected by water displacement.. ................................ Know that zinc displaces silver ions from solution. ........ Know that gas escapes through an unsealed thistle tube.. .. Observe that delivery tube is below surface of liquid in the generator ........................................... Know that in electrolvsis of brine.. (NaCI): . a . Chlorine collects a t electrode.. . . . . . . . . . . . . . . . . . collects a t - electrode.. . . . . . . . . . . . . . . . . b. Hydroam c. Sodium hydroxide is formed.. ...................... Know that in the electrolysis of a solution of potassium chloride: a. Chlorine collects a t electrode.. . . . . . . . . . . . . . . . . . b. Hydrogen collects a t - electrode.. . . . . . . . . . . . . . . . . c. Potassium hydroxide is formed. . . . . . . . . . . . . . . . . . . . Know that in electrolysis of water: electrode.. . . . . . . . . . . . . . . . a. Oxygen is liberated a t b. Hydrogen is liberated a t - electrode.. . . . . . . . . . . . . . Complete apparatus. The conditions of reaction and the ~rooerties of the ~ r o d u care t given.. ................... . . . Observe incorrectly set up apparatus: a. Use of Bunsen burner in the preparation of hydrogen. . . b. Shart thistle tube, gas escapes.. . . . . . . . . . . . . . . . . . . . c. Short thistle tube and long delivery tuhe reaching liquidingenerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
+
~
+
+
~
T h e data just presented i n t h i s study does not yield itself readily to comparative consideration, but m u s t b e considered o n its own merits. One or t w o comparisons m a y be m a d e with data obtained by PowersS in making the survey of student achievement in the subject m a t t e r of high-school chemistry. Powers found that 85.9% of t h e s t u d e n t s tested understood Powers, Samuel R., "A Diagnostic Study of the Subject Matter of Hiih-School Chemistry," Tsachers College Contribution to Education, N o . 149.
electrolysis of water. In the present investigation with a labeled drawing provided, 35.3% indicated that oxygen was collected a t the positive electrode, while 45.3% knew that hydrogen was collected a t the negative electrode. The results in the electrolysis of a solution of sodium chloride practically check with those obtained by Powers. There are not many points for making comparisons with other tests which are essentially based on the text material. A summary of the results obtained in this investigation does not warrant definite conclusions. It is true that a study of the test results indicates some interesting tendencies, and encourages one to believe that it may be possible to measure with some degree of accuracy the laboratoly technic as a product of the laboratory practice. The extent to which such objective measurement will be possible will require further investigation. It may be suggested that in continuing the work of this study, attention should be directed in determining the practice effect developed by giving occasional tests of this nature following closely upon the completion of the laboratory assignment. Such investigation will assist in arriving a t more definite conclusions.
