Karen W. Morse Utah State University Logan, 84322
A Laboratory Course for Students in Science-Related Fields
Many colleges and universities must offer a chemistry laboratory course which is primarily a service course, i.e., i t is offered to train students in chemical principles and techniques utilized in a field of study other than chemistry. We have recently revised our chemistry laboratory (Chemistry 144) which fits the above category and which is taken by students majoring in such fields as dairy science, wildlife, forestry, animal science, soil science, nutrition and food science, plant science, range science, agricultural education, forest ecology, nursing, etc. The following objectives were implemented into the revision program 1) Prepare and train students in principles and techniques
which are required for their major field of study. A personal request far data relating to the needs of majors of departments reouirine n the laboratow enabled us to collect and evalunw the most wlunhlc principles and teohniquca to be incorporated into the lalmrsfory. (See the table.) 2) Stimulate student inwrest in t h e laboratory manipulations so as to more effectively train them and obtain responses from them in the laboratory situation. This was accomplished by (1) using material with which the student was familiar on an everyday basis (e.g., fluoride in toothpaste, Accent* as an amino acid) and (2) pointing out to the student the relationship of the experiment and its principles and techniques to hisher major field of interest. This was done by distrihuting to each student, sheets as in the tahle (examples of application of each experiment to each major field had been requested from the appropriate department; the example shown is from the Animal Science Department). 3) Maintain a high level of scientific approach in both the chemical principles and the techniques. ~~
~~
~
7~~~
A summary of the project results is as follows. Discussion Revision of Former Experiments
Gosolrne: In order to more pointedly illustrate the separation of components of a mixture by distillation (gasoline, of course, could not be separated into components by a simple distillation), two liquids which would be components of crude oil were found which could be separated with a simple distillation apparatus. The two components, pentane and cyclohexene, were examined chemically (reaction with Brz water and KMn04) and physically (density) to enable the student to identify them. Pollution: A Test for Nitrate in Water (I): This experiment was made workable hv changes - in concentrations of the reagents used. Properties of Colloids: This experiment was reorganized so that the properties of colloids (e.g., smoke, gels, coagulation, diffusion, Tyndall effect, emulsions) could be compared and illustrdted without questmn. The write-up was made more exfensloe so that the student could understand what was happening on a molecular level. Amino Acids: Paper chromatographic separation of several amino acids and chemical tests (ninhydrin, Millon's, nitrous acid) for particular amino acids were chosen with appropriate concentrations for reagents determined for the Presented at the 161th National ACS Meeting, Los Angeles, California Aoril. 1974. Division of Chemical Education. General Papers, No.22. 316 / Journal of Chemical Education
latter so unequivocal results could he obtained by the students. New Experiments Developed as Usable in this Program
Fluoride Determination in Commercial Toothpaste (2): A spectrophotometric determination of fluoride content of t o o t h ~ a s t e(rather than natural water sources because the concentrations are extremely low in our area) was carried out on Crest@ toothpaste. Volumetric techniques are required as is the use of an analytical balance and spectro~hotometer.The percentage of fluoride calculated is compared to results.' Chemistry of Paint Pigmentation (3): A paint pigment, PbCrOl, is prepared using a gravimetric procedure. Principles illustrated are amphoterism, oxidation-reduction, equilibrium dependence on pH, quantitative precipitation, use of an analytical balance; polymerization (drying of paint), and a qualitative test for paint (1%)in paint samples are also examined in a follow-up experiment (4). Determination of Potassium in Cocoa: The eravimetric method is used to determine the potassium content of cocoa. Volumetric techniaues are also reauired. Calculation of the percent of potassium is carried out by assuming all the precipitate is present as potassium tetraphenylhorate. Glucose Leuel in Blood (5): The change in the glucose level in the blood is examined after a fasting period and after periods of 45 minutes and one hour and 40 minutes after drinking a concentrated glucose solution. The collected hlood samples are centrifiged, the serum is separated out and then treated with an indicator; the resulting colored solution is measured using a spectrophotometer. Commercial glucose samples may also he used as the unknown. Comnarison to a standard curve established hv the student using standard glucose solutions gives the glucose level in the blood. Determination of Hardness of Water and a n Example s to the lahof Water Softeninn (6): Water s a m ~ l e hroueht o i a t o r y b y 'the students are titrated to Zeteimine the amount of Ca2+ in the water. pH, buffer action, and the effect of a foaming agent are also illustrated and discussed in detail. Pigments in Plants: A separation of pigments in plants was carried out using thin-layer chromatography. Comparison of the different pigments from different sources is made and common pigments are identified when possible. New Experiments Found to be incompatible on the Freshman Level
Pollutants: Analysis of Automobile Exhaust for Nitrogen Oxides (7): Several different methods of analysis were employed to try to develop this into an experiment which could be used on the freshman level. Evidently, it is too complex a reaction or procedure to he used thusly. Major problems were encountered in collection of the sample, storage, (with relation to decomposition), and determination of content of the collected sample. I t was extremely difficult to get consistent results in that the results varied with changes in idling speeds of the engine, the length of time the car was warmed up, and the efficiency of the methods of getting a constant gas stream from the exhaust pipe. All of these factors were very difficult to control with
Sample of Table Given t o Each Student Taking the Laboratory MAJOR F I E L D :
Animal Science
N A M E : Dr. J. Street
PHONE EXT. NO.
7424 Exampler of Value t o Your Major andlor Use i n Your Majora
Procedures
valuation of commercial Vinegat
colloids
Aspirin ryntherir
(a) Determination of fluoride in toothpaste (also) (b) Pollution nitrate analysis
'.Accent" on Amino Acid ChromotograDhY
Chemistry involved in the preparation of a lead con. taining paint pigment
Acid-Base R e a d i o n l Equivalency (endpoint) concept of p H Use of indicator for endpoint detection ~ i r t i l l a t i o n(evaporationcondensation) Reactions of saturated and unsaturated organic compounds Density SoIUbilitie6 o f liquldr in liquids, rolidr in liquids Saturation, ruperraturation Identification and reparation o f material5 baled on solubilities Properties of ColloidS gels, ralr, smoke Diffusion Adrorption ~ y n d a leffect l (light scattering) Organic ryntheris Precipitation Filtration (vacuum) Recryrtallilation Esterification colorimetry (a) rpectroDhotometric determination (b) Viruai determination Papel Chromatography RffaCtor Ammo acid characteristics and reactions.
Quantitative Precipitation Oxidation ELIUilibIiUm deoandence on p H Semi-quantitative chemiical tests t o determine presence of lead
Use of volumetric equipment Titration Use of p H meter
soil testing, rllage, and rumen evaiuationr. Clinical blood and urine testing.
DiLiilatiOn Graphing use of analytical balance
Fats, unsaturated verrur saturated (physical props,, hydrogenation of, iodine no., rancidity).
Supersaturation Seed cryrtalr Quantitative roiubilitv
Relationship t o toxic ions (CaF, versus NaF). Nutritional availability of various Dhorphate salts.
Preparation of colloids General laboratory handling of chemicals
Natural erterificationr, as in fat ryntherir; digestive hYdlOiYli6 of esters.
use of a spectrophotometer
use of a volumetric glar* ware
Use of paper chromatographic Method for determination of unknown Test tube reactions of amino acids as a means of identification Gravimetric techniques: precipitation quantitative transfer of a precipitate Use of a n analytical balance
spectrophotometer Vit. A and carotene array. spot test for toxic levels o f NO;
in feeds.
carotene arsay in feedr;amino acid com position of foods: ChromatDgraphy in analysis of vitamins. pesticide$, veterinary drugs, feed additives (rtilbertroll.
Feed analyses (ash celluiore, lignin, calcium. sulfur). Diagnosis of lead toxicity ($Dot tertr of ingests).
a b s t column completed b y each department requiring one-duirter laboratory from their majors
inexpensive lahoratory equipment available on the freshman level (as balloons, water displacement equipment, etc.) Determination of Chloride in Water (8): The tests for the chloride content of water turned out to he very sensitive to technique as the endpoint determination was extremely subtle. Since the student a t this level has a very limited technique developed, we felt that this was not the best titration experiment that could he used. Properties of Indicators Made From Plants: The use of huckleberry, raspberry, and cherry juices as indicators was explored. Color changes do take place at particular p H levels, hut these changes were not abrupt enough to he used as the basis for endpoint indicators. Videotapes In order to aid in demonstrations of techniques and equipment, videotapes were produced dealing with the use of the analvtical balance,. .D H meter.. s~ectro~hotometer. . and the procedures of filtration, titration, and distillation. The tapes were made in such a way that they are applicable to any beginning lahoratory and, thus, can he utilized by other members of the faculty. Summary The results of the project were evaluated hy a student evaluation form in which 98% of a group of 60 students
stated that they believed the laboratory to he worthwhile not only in terms of being interested and stimulating, hut particularily in relating to future work that they might he involved in. There is no doubt that the manner in which the course was developed and the resulting experiments favurably increased relations with other departments on campus in addition to improving the kind of chemistry Inh~ r a t &offered ~ to the no;-chemistry major type of student. Acknowledgment We wish to express our gratitude to students of Chemistry 144 who have greatIy aided in the development of this lahoratory. Gratefully acknowledged is support received from a Research and Training Fund through the Provost's Office and also funds from the College of Science. Project workers were Dr. Dean Adams, Larry Thorne, and Terri L. Daines (2,3,5). Llterature Cited (1) King,D. M.,Lampinan,G. M.,and SmithIII, J. H., JCHEM.EDUC.,48.647 (19711. (21 Daines. T.L., and Morne. K. W., J. CHEM. EDUC.. 51.680 (19711. (3) Dsinea, T L..and Morse, K. W. J. CHEM. EDUC., Aeeepfed for publication. (41 Keplan, E.,and Shaulli.R.S..Amer. J. Public Heoith. 51.65(19611. (5) Daines.T. L..and Mone. K. W., J. CHEM. EDUC.. Aceepted for publication. (6) '"StandardMethods for the Examinationof Water and Wastewater: American Publ i e Health Association. Washin@ton,D.C., 1971,p.76. (71 McFarBnd,J. H.,end Benton,C.S., J.CHEM. EDUC.,49,21 (19721. (8) Refaronce (GI, p. 97.
Volume 53. Number 5, May 1976 / 317
