LECTURE DEMONSTRATION ON HYDROGEN* C . S . ADAMS, ANTIOCHCOLLEGE, YELWWSPRINGS, OHIO
Lecture demonstrations, particularly in the field of college freshman chemistry, have always played a very important part in chemical education. The early masters were known for their brilliance in demonstrations. And yet, in the recent discussions of chemical education, both in our jonrnals and meetings, the subject has been neglected. The symposium on lecture demonstration, which the Division of Chemical Education held a t the Columbus meeting of the American Chemical Society, introduced this very important field for investigation. It seemed wise.to canvass the colleges and universities for information relative to what is being done in the way of freshman chemistry lecture demonstrations. A questionnaire was designed for this purpose and sent out to 290 different colleges and universities. The list of colleges was obtained from the Bulletin of the American Association of University Professors. This list included a convenient number and practically all of the larger universities and colleges. The questionnaires were sent out on March 15th. Answers to 144 have been received to date. The answers received include practically all of the larger universities and colleges. Lecture demonstrations have developed along with our newer ideas on chemistry. Most colleges and universities have developed their own collections of lecture demonstrations. The introduction of the college glass blower has encouraged the development of original and more effective apparatus. Very few of these new demonstraJions have heen published. The few which have been published are scattered through our journals in such a way as to make them more or less unavailable. The following books give information: NEwH, G. S., "Chemical Lecture Experiments," Longmans, Green & Co., 55 Fifth Ave., New York City, 1892. HE~uNN, K., "Anletung zum Experimentieren," Friedr. Vieweg & Sohn, Brauuschweig, 1893. ARENDT,R., "Technik der Experimental Chemie," Voss, Hamburg, 1900. BENEDICT, F. G.. "Chemi~dLecture Experiments," Macmillan Ca., 60 Fifth Ave., New York City, 1901. DAVISON, H. F., "A Collection of Chemical Lecture Experiments," Chemical Catalog Co., Inc., 419 Fourth Ave., New York City, 1926. (Good hut incomplete.) Scmpo, K., "Vorbereitungsbuch far den Experimentaluntemicht in Chemie," Teuhner, Leipzig. 1926.
The first four books are good but out of date; the latter two are incomplete. Other than these books no organized attempt has been made to obtain
* Presented before thc Symposium on "Lectur< I~xperimenmtion."I)ivi\ion of Chemical Education, at the 7:th Neering of the Amcriran Chcmical Sucietv. Columbu~. 1882415 ~, Ohio, April 29 to May 3, 1929. For other papers see THISJ O U R N & , ~ (Nov., 1929). 349
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this information from various colleges and correlate it for use in various courses in chemistry. The questionnaire was divided into two parts: (1) General. The object was to get the attitude of colleges and universities on the value of lecture demonstrations and conditions under which they are given. The answers to this part also helped us to better evaluate the latter part. (2) Hydrogen. The object was to find out what experiments are being used i n lecture demoizstrations on hydrogen. The author wishes to state here that there is no claim that the questionnaire sent out was complete or even adequate. In fact, the results indicate that i t ought to he revamped if this method of investigating the subject is continued. It is even a question whether better results could not be obtained by a different method of approach. If the questionnaire helps to open up and stimulate interest in the field of lecture experiments, it will have accomplished its objective. The following data have been tabulated from the answers to these questionnaires. Since in many instances questions were not answered or the answers did not permit of classification, it is impossible to give complete data. Questionnaire. I. General 1. Name of college or university. 144 answers to questionnaire received. 2. Number of ledurers in freshman chemislfl. Number of lecturers
*'
Number of eolleger
1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
3 (a). Length of Lecture period. Length of lecture period
Number of colleges
25minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Onehour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Twohours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 ( h ) . Number of lectures i n course. For those.with high-school chemistry, average. . . . . . . . . . . 40 For those without high-school chemistry, average.. . . . . . . . 110 4.
Approximale number of studenls i n room during leclure. Number of students
Number of colleges
1-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 51-100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 101-150 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 150-. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Do you giw ledure demonstrations i n freshman chemistry? 5. Number of colleges answering "yes". . . . . . . . . . . . . . . . . . . . 114 4 Number of colleges answering "no". . . . . . . . . . . . . . . . . . . . . 15 Number of colleges answering "limited number". . . . . . . . .
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6. I n general what fraction of the lecture period i s actually devoted to demonstrations? Average between one-quarter and one-half depending on nature of subject . 5 schools answered "none." Varies greatly . 7 (a). I n general do you believe that demonstrations should be short (not over 5 minutes)? Schoolsanswering "yes" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Schools answering "no" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Schools answering "varies" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 The comments on this question were very interesting. There was an almost unanimous agreement that experiments should be short, simple. pertinent. and decisive. (6). I n general do you belime in simple demonstrations? Schools answering"yesW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 :-hods answering "no" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Schools answering "reasonably" . . . . . . . . . . . . . . . . . . . . . . . . . 2 (c) .
8.
I n general do you believe in speed i n ezecution of exfieriments? Schools answering "yes" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Schools answering "no" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Schools answering "workable" .......................... 9 Do you maid the use of demonstrations i n which ezplosions occur or pm'sonous fumes are evolved? Yes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 Wherepossible . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Not necessarily . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Avoid fumes only . . . . . . . . . . . . . . . . .I. . . . . . . . . . . . . . . . . . . 8 Avoid explosions only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
*.
9. Do you m a k e a distinction i n the list of lecture demonstrations giwa before those who hase had and those who haoe not had high-school chemistry? Yes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Some . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Do you supplement your lectures with lantern slides? 10 (e). Yes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61 No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Use motion pictures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Do not use slides. but would like to or are going to. etc .... 4
(b). If so. in how many of the total number of lectures i n fwshman chemistry do you use slides? Varies. Depends upon subject considered. I n general do you belieue i n the inclusion of demonstrations of historical sig&%ance? 11. Yes ................................................. 39 No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Afew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Normal* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 *"Normal" includes those who said "only if experiment has practical value aside from historical value. " etc.
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12. State briefly your mun feeling as to the oalw of lecture demonstrations. The comments on this question were as interesting as they were varied. I n general there wils an agreement that lcctwe cxperimcnts s e r e invnluablc ehen urrd to explain and illustrate the subiect but uselcss and e r m harmful when presented as "stunt%" or "shows." In fairness to a minority opinion expressed in answer to this question, i t should be stated that this group believes lecture experiments and lectures are a byproduct of wholesale education. Under ideal conditions for teaching chemistry, this group would do away with both lectures and lecture experiments. The author hopes to present a separate article on the comments to this question.
Jz.
Questionnaire. 11. Hydrogen 1. State the number of lectures devoted to hydrogen.
Is the subject of hydrogen taken up near the beginning of the course? Yes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Do you use lantern slides? Yes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1W Would like to, but don't.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Use motion pictures.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Motion pictures used were: Industrial uses of hydrogen and acetylene; electrolysis of water; historical and industrial. 4. Please list the lecture demonstrations which yo% giw on hydrogen to your freshman P chemistry classes. (a). Preparation of hydrogen. The following experiments arethe conventional ones unless otherwise stated. Experiment Schoois demonstrating ( I ) Eectrolysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 (2) Metals and son-metals on water a. Na B O . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 b. K HIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 c. Ca HzO. . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 d. M g HzO. . . . . . . . . . . . . . . . . . . . . . . . . . 30 e. Fe HxO... . . . . . . . . . . . . . . . . . . . . . . . . . 5$ f. C H 2 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 g. Hydrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 (3) Metals on acids 83 e. N a HC1.. ..... 1 64 f. Zn +variousacids 12 c. A1 56 g. Cu HCI.. . . . . 4 32 Pb HC1.. . . . 1 (4) Metals on bases a. Zn NaOH.. . . . . . . . . . . . . . . . . . . . . . . . 28 b. A1 + N a O H . . . . . . . . . . . . . . . . . . . . . . . . . . 26 c. Zn NaOH.. . . . . . . . . . . . . . . . . . . . . . . . . 4 (fused in crucible) 2.
+
+ + + + +
+ +
+ +
+
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( 5 ) Miscc1laneous n. Recovery from water gas . . . . . . . . . . . . . . . 1 b Si NaOH . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
.
+
.
(b) Properties of hydrogen ( 1 ) Physical
.
.
a Taste. odor. color. solubility . . . . . . . . . . . . . 59 b . Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 c . Diffusibility . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 d Soap bubbles . . . . . . . . . . . . . . . . . . . . . . . . . . 32 e. Catalytic ignition by platinum black . . . . . 13 f. Effect of inhaling.HZon voice . . . . . . . . . . . 2 g . Adsorption in platinum or palladium . . . . . 18 h . Contraction in volume of 2 8 Os 4 2 8 0 (steam) . . . . . . . . . . . . . . . . . . . . . . . 1
.
+ ~
~
(2) Chemical
.
a Combustion of H. . . . . . . . . . . . . . . . . . . . . . . 93 b . Explosiveness. . . . . . . . . . . . . . . . . . . . . . . . . 80 c . Reducing action: CuO Hn. . . . . . . . . . . . 64 d . Zn Hs KMnO (nascent Hn)........ 4 e H2 Cln . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 f . Hydrogen siren or singing flame . . . . . . . . . 1 g . Sodiumamalgam. . . . . . . . . . . . . . . . . . . . . . 1 h. H l + S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 i . HgO Hz. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 j . FeaOd HZ. . . . . . . . . . . . . . . . . . . . . . . . . . . 1 k . Atomic hydrogen . . . . . . . . . . . . . . . . . . . . . . 1
.
+ + +
.+
+ +
(c)
.
.
Uses of hydrogen C a . Blast torch . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 b . Atomic H2 blast torch . . . . . . . . . . . . . . . . . 4 c . Hydrogenation of fats . . . . . . . . . . . . . . . . . . 44 d . Balloons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 e CO 2Hz -+ methanol . . . . . . . . . . . . . 2 f . Use: making NH3. . . . . . . . . . . . . . . . . . . . . . 1 g. Oxyhydrogen welding auffit . . . . . . . . . . . . . 1 h . Municipal gas . . . . . . . . . . . . . . . . . . . . . . . . . 1 Colleges for whom no experiments are listed or indefinite answers given Usual experiments only . . . . . . . . . . . . . . . . . . . . 15 Noexperiments . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 D o not teach elementary chemistry . . . . . . . . . . 2 Did not answer questions on hydrogen ....... 7 Are experimenting with course . . . . . . . . . . . . . . 1 1 Naneasarule . . . . . . . . . . . . . . . . . . . . . . . . . . . . Do not treat hydrogen this way . . . . . . . . . . . . . 3
.
+
.
Conclusions 1. The answers to the questionnaires indicate a very definite feeling in favor of lecture demonstrations in freshman chemistry. There were a few colleges who did not give lecture demonstrations but would if facilities
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permitted. A few doubted the value of any demonstrations not performed by the student himself. 2. The author hoped that many'new experiments and original ways of presenting older experiments would be found in the answers received. In this the results were somewhat disappointing, indicating that colleges, in general, present the conventional list of experiments illustrated in the usual college textbook. There were a few experiments and modified apparatus suggested which will be described in a later paper. The nature of the subject might easily account for the dearth of new demonstrations. A subject such as "The Gas Laws" would undoubtedly bring in many new types of apparatus. 3. Opinion was almost unanimous in that lecture experiments should be short, simple, pertinent, and decisive to be effe6tive. In general, lecture experiments should not duplicate the laboratory experiments. 4. The questionnaire sent out revealed certain weaknesses which should be corrected in any future attempt to secure similar information. It was too long to get the details necessary for proper analysis. A few of the questions were not clear, resulting in ambiguous and indefinite answers. 5. Whether the questionnaire method is the proper way of obtaining information on lecture demonstrations or whether some other method is preferable, the author feels that such information ought to be collected and made available through THISJOURNAL.
Greenest Plants Grow Most Efficiently. Plants whose leaves contain the most chlorophyll, the stuff that makes leaves green, are the most efficient a t the husiness of making new plant tissue-which is, from the farmer's point of view, the chief end and object of plant existence. Ever since pioneer plant physiologists found out what chlorophyll is, and learned that its function is to capture carbon dioxide out of the air and with the help of sunlight to combine it with water t o make sugar, it has been taken for granted t h i t the more chlorophyll a plant has per square inch of leaf surface the faster it can make new stems and leaves. It has remained for Dr. H. B. Sprague and Dr. J. W. Shive of the New Jersey Agricultural Experiment Station to determine the relation accurately, using the exact analytical methods of the chemical laboratory. They have recently reported their results in detail to the American Society of Plant Physiologists. They grew standardized breeds of corn under carefully controlled conditions. They supplied nutrient chemicals a t a known rate. They measured the areas of leaves, extracted the chlorophyll and determined its quantity per square centimeter, and weighed their plants as they harvested them. Correlating their data, they found that the strains with the most chlorophyll per unit area had produced the most cornstalk in a given time. They also found that the plants which produced the greatest spread of leaves were most efficient a t the business of growth. A yellow pigment, carotin, which is found in leaves, bore a similar relation t o the rate of new stalk and leaf production as did the chlorophyll.-Science Sem'ce
