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Fifteen Years with a Nonacademic Chemistry Course C. LeRoy Darlington Montclair High School, 100 Chestnut Street, Montclair, NJ 07042 In the spring of 1966, it had become evident to us a t Montclair High School that the CHEM Study course was not suited for students who were unable to do well in mathematics or in related forms of logical quantitative reasoning. Yet we had a sizable number of iunior and senior students who wanted to take a t least one more science course in addition to their ninth-zrade earth science and tenth-zrade biolorv. Up to that time, many students bad heen advised against taking chemistry if they had difficulty with mathematics. Those who persisted and for whom the CHEM Study course would have been unsuitable were steered into our Nursing Chemistry course. This did not prove to be a very successful alternative, and the time was ripe for a new course in chemistry. (The Nursing Chemistry course was eventually dropped.) nrovide The maior ohiectives of the new course were (1) . . to . students with a broad, general understanding of chemistry and its role in their lives: (2) to ~ r o v i d ea course that did not require much more than a minimal understanding of basic arithmetic: and (3) to provide a stronn and widelv diversified laboratory program. These ?bjectivei have provkn to be satisfactory and remain as valid todav as thev were 15 years ago. The new course was started in September 1966, and literally evolved as we proceeded through the year. Since there were no textbooks designed for such a course, I had to use what we had on hand-a eeneral chemistrv textbook nuhlished in 1957. This text provicied only a skeleton of what'l needed. A later edition of the book oroved to be more satisfactorv for mv
LeRoy Oarlington rcce veo ne B a c n e l a ' oegree ~ n Chem stry lrom Swarmmore Co. ege n 1942 an0 n 5 Ma51er's aegree in t d u c a t m from Temp e Uni-
and quantitative material. This was consistent with textbook publishing practices fur science hooks in the post-Sputnik era. After "muddling through" materials that I felt were less than satisfactorv. I used the exnerience that I had aained in teaching this course since 1966 to write my own text, "Chemistry and Modern Civilization." This was printed in and
thl, m;ttvrinl wii.; nwrganizd i d puldichcd in 1977 Ht,uyl,tlr \ l ~ t t l ; n(.'ornptuny 8.;" T h e Clwmirnl World"
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hy the 121.
The Nuts and Bolts of the Course During the past several years, the units that have been included in our course a t Montclair High School have been Water, Air, Matter and Energy, Atoms, Forces between Atoms, Carbon-The Remarkable Joiner, Petroleum and the Automobile, Compounds Built on a Hydrocarbon Skeleton, Foods, Polymers, Acids and Bases, Nuclear Energy. Watef Whenever possible, we have attempted to introduce students to major concepts through experiments in the lahoratory. In the opening unit on "Water," students measure the hoiling point and freezing point of water and the effect of dissolved solids on the boiling and freezing points. Students exnlore the behavior of saturated. unsaturated. and sunersaturated solutions. The soluhilit; of a salt is measured a t different temperatures, and students plot a solubility curve.
versily in 1951. He has taken advanced studies in chemistry and related sciences at numerous universitie~.Roy has 35 years of teaching experience in high school chemistry, the last 16 yearsat MontClair High School. Montdair. NJ. In addition. Mr. Darlington has had numerous experiences at the industrial level. Montclair High School. located in a sfable, integrated suburban community of about 44,000 residents. has an enrollment of 2100-2200 students. Tne sl~ounl110~)Cons st? of approxlmaw 60% *n le an0 40"" olacr blbdenls n an average year 6 5 ' j of the graddales attend four-year r o l eger while another 15% enter junior colleges, nursing SC~WIS. or technical institutions. The Science Department at Montclair follows a plan of homogeneous grouping-the most able students placed in the "one" group while the least able students in the "three" group. No student is forced into a particular group and may elect to transfer from one group to another. Mr. Darlington describes in this paper the chemistry course designated at the "three" level. As a result of his
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teaching experiences. Roy has co-authored two textbooks-"The Chemical World" (1) and "Chemistry: An InvestigativeApproach
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The purification of dirty water by filtration and distillation is performed in the lahoratory. In their reading and by viewing motion pictures and filmstrips, students learn about the practical problems of water purification on a large scale. The complexities of water and air pollution are thoroughly examined. Air Students prepare oxveen and carbon dioxide in the lahoratory at thk start of this unit. The relative reactivities of maenesinm. steel wool, and wooden splints are tested in these . gases, as well as in nitrogen and argon. Various aspects of the combustion process are examined throueh . experimentation . and demonstration. These include comparing mass changes during the combustion of steel wool and a candle; examining the cokhustion products of complete and incomplete burning; kindling temperature; the effect of surface area on combustion rates. This last test becomes ~articularlvrelevant when the knocking characteristics of linear and hranched chain hydrocarhons in gasoline are studied later. Matter and Energy The kinetic-molecular theorv of matter is examined on a qualitative basis. During the; lahoratory work, students discover the direct relationship between temperature and pressure of gases, as well as between temperature and volume. The inverse relationship between pressure and volume is also studied. Students learn how to explain these relationships on the basis of molecular motion, but no calculations are attempted. The effect of molecular motion on phase changes is also discussed. Atoms Students are introduced to the study of atoms by a demonstration of the hehavior of chareed interac" narticles-the . tion between like charges and unlike charges, as well as the effect of distance on the force between charges. In the laboratory, class members simulate Rutherford's scattering experiment by systematically rolling small steel balls through boxes containing unseen objects. By observing the directions in which the balls are scattered, students predict the location, size, and shape of the objects within the boxes. Following the examination of flame tests of chlorides and nitrates of sodium, potassium, lithium, calcium, strontium, and copper, students study the emission spectra of some of these and other elements. They make drawings of six or eight spectra and use their drawings to identify an unknown element. On the basis of the preceding demonstrations and experiments, students are led throueh the reasoning Bohr used in hut not emphasized.'~tudentslearn how to allocate electrons to the maim energy levels for elements with atomicnumbers dot symbols for the elements. Electron dot symbuls are used to help students write formulas for covalent compounds. By using ionic charges, students learn to write ionic formulas. In the lahoratory, students conduct a numher of chemical reactions. for which thev write word equations. Formulas are then substituted for woris, and students proceed to learn how to balance equations. Two laboratory experiments have been designed to make it possible for the students to gain an understanding of quantitative relationships existing in formulas and in equations without eettine lost in mathematics. In the f i r s t i f these experiments, students describe the empirical formula of zinc chloride by reacting a known mass of zinc with excess hydrochloric acid. The mass of zinc used, 0.65 g, is choosen so that the digits in this number are the same 712
Journal of Chemical Education
as the digits in the approximate atomic weieht of zinc. 65. mass of about 35 amu to give ZnCl with a mass of about 100 amu. If two atoms of chlorine reacted to give . ZnCl,, the resulting mass should be ahout 135 amu. When 0.65 g of zinc reacts with excess HCI, the class average for the mass of zinc chloride formed is always very close to 1.35 g. From this, it is easy to show that the formula for zinc chloride must he ZnCl?.
atom of iron with an atomicweight of about 56 produces one atom of copper with an atomic weight of about 64. No further calculations involving mass-mass, mass-volume, or volumevolume relationships are attempted. Carbon Students are introduced to organic chemistry by building styrofoam models of a number of hydrocarbon molecules, as well as other molecules involvine carhon. hvdroeen. and oxygen. Toothpicks are used for hinds. ~ t ~ r o f o a m h lare is used instead of hall-and-stick models, because stvrofoam halls without holes give the students no clues about the numher of bonds required by each of the elements. structures and electron dot symbols. ~ y d r o g i n(small balls) must always have one bond. Oxygen (medium halls) must always have two bonds. Using models, students explore the structure of saturated and unsaturated compounds; linear, branched, and ring compounds, as well as isomers. Class members draw structural formulas from their models. In the lahoratorv. .. students immerse 10-ml samnles of n hexane, n-heptane, n-octane, and isooctane in vegetahle oil baths and measure their hoiline.. points. This clearlv shows the . relarimwhip OCIWPQII chain I P I I ~ I I dI . l~i n ~ ? l~r ~ m p ~ , u n d s their h t ~ ~ l ~ puint.. n n 'The t.ifect Ihe Imnchinr c.1 hvdrcscarhon chains bn the hoiling point is also easily obser;ed. The small size of the samples and the use of an oil bath makes this a safe experiment conduct. An occasional minor fire is quickly extinguished by merely blowing on it sharply. This experiment helps clarify the nature of the weak forces between molecules of hydrocarbons. Later, when the low hoiling points of hydrocarbons are compared with the higher boiling points of alcohols having the same number of carbon atoms, the concept of polarity with the resulting stronger intermolecular forces is discussed. Petroleum and the Automobile In this unit, students learn the elementary facts about internal combustion engines. Simple models suitable for overhead projection are borrowed from the auto mechanics department. Students conduct fractional distillations of 10-ml samples of hydrocarbon mixtures made from gasoline, kerosene, and light motor oil that approximate the composition of crude petroleum. The relative boiling points and the flammability of the distilled fractions are compared. After viewing an excellent film on "Refinery Processes" distributed free by the Shell Oil Company, the class examines in some detail fractionation. crackine. oolvmerization. ~~-~isom". . erization, and hydrogenation. The effect of molecular structure on the anti-knock characteristics of pasoline is studied. The advantages and disadvantages of tet4ethyl lead are also considered. The attention of the class is brought again to problems of air pollution and its prevention, as well as to the problems of present and future fuel shortages.
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Students compare the viscosities of various grades of motor oil a t different temperatures by dropping large marbles into samples of the lubricants contained in 100-ml graduated cylinders. For each oil sample a graph is plotted showing the relationship between temperature and the time it takes for a marble to fall through the liquid. Hydrocarbon Skeleton
Students prepare ethanol by fermenting sugar and distilling the product. Compounds formed by the mild, strong, and comolete oxidation of alcohols are prepared in the laboratorv. . . simple esters are produced; aspirin is made and purified by recrvstallization. The puritv of the product is tested hv measuring its melting point. Finally, different brands o? commercial aspirin are titrated with sodium hydroxide to show that the aspirin content of all five grain tablets is essentially the same. Foods
Students examine properties of carbohydrates, proteins, saturated and unsaturated fats, vitamins and minerals. Different food samples are tested with Fehling's or Benedict's solutions. The relative difficulty of hydrolyzing different carbohydrates is measured. Students extract peanut oil from peanuts and determine the percent of oil in the nuts. Soap is made by reacting sodium hydroxide with either lard or hydrogenated vegetable oil. The moisture and fat content of different meat samples are measured. The vitamin C content of a number of fruit and vegetable juices is determined by titration with iodine. Before completing the "Foods" unit, class members keep a record of what thev have eaten for three dam. Bv comoarine . " their actual diets with a recommended diet b k e d bn the Basic Four Food G r o u. ~.sthev . " find how satisfactorv or unsatisfactory their eating habits are. Poiymers
Students auicklv recoenize that their studv of carbohvdrates and proteins has-already introduced'them to this subject. In the lahoratory, l-g samples of cellulose nitrate are prepared. The relative flammabilities of cellulose, cellulose nitrate, and cellulose acetate are compared. Plastic films of cellulose nitrate are prepared by evaporating a solution of = cellulose nitrate in ethyl acetate. The class studies addition polymers and condensation polymers. Small amounts of polystyrene and polymethylmethacrylate are produced hy class members. The formation of nylon is demonstrated. Students compare the properties of crude polymers made by condensing ethylene glycol-adipic acid mixtures and glycerol-adipic acid mixtures. The production of a thick oil made by using ethylene glycol is compared with a tough, resilient mass made by using glycerol. This clearly demonstrates the effect of cross-linking. Vulcanization and other applications of cross-linking are studied. The properties of thermoplastics and thermosets are examined. In some classes, students have worked with commercial molding compounds to produce various free-form artistic objects. The tensile strength of natural and synthetic fibers can he compared by measuring the load required to break them. Other experiments comparing the flammability of fabrics, the properties of natural and synthetic elastomers, and the properties of plastics are also possible. Time is the limiting factor, however, and some experiments must he omitted. Acids and Bases
By the time theclass reaches this unit, they have already worked with organic acids and have used most of the common
of soap. Calcium hydroxide has been used in testing for carbon dioxide. General oro~ertiesof aaueous acids and bases are studied. The re1ati;e strengths of acids and bases are demonstrated with a conductivitv demonstration and hv a simple reaction rate experiment. Molaritv is touched on only hrieflv. Students measure the concentration of unknown acids hy titration. By now, the class is beginning to become quite adept a t performing titrations. They have already titrated aspirin and vitamin C in earlier experiments. Before completing this unit, students hecome familiar with the pH scale and make simple pH measurements. Sulfurous and sulfuric acids are prepared. This experiment is followed by a discussion of air pollution and acid rain. Nuclear Energy
It has always been a problem to find time for the final unit. For two or three years this unit was dropped. At the time of the Three Mile Island incident, however, evervthine else in the course was pushed aside, and the probl'ems aisociated with nuclear changes were tackled with great enthusiasm. It has become apparent that this area is so;mportant that it should he included each year. How much can he done in the lahoratory with nuclear energy depends on the equipment availahle. Each school should have a minimum of one simple Geiger counter; one alpha, one beta, and one gamma source; and one cesium-barium"minigenerator." If only one Geiger counter is availahle, the teacher can perform the required manipulations, while the students record the data. Depending on the time availahle, a number of demonstrations and experiments are possible. The operating charac-
radiations can be easily measured bv placinp.varying . . numhers of cardboard, aluminum, and lead sheets between the appropriate sources and the Geiger tube. The relationship between the distance between each source and the recorded count can he studied. Since the half-life of the harium-137m produced by a cesium-barium minigenerator is only 2.55 min, an entire half-life demonstration requires only about fifteen minutes to perform. Included in a study of nuclear energy should he the nature of radioactive decav, other nuclear reactions. nuclear eauafission reactors, the potential of fusion reactions. Scientific Literacy and Responsibility
Throughout the years, most of the students who have taken this course have been drawn from the lower half of the junior or senior classes. Before enrolling in the course, they have been told that this course provides them with a lahoratory course reauired bv some colleees. orenare " . but that it does not . . them for a future in any professional area of science. A number of students have cone to iunior colleees, communitv colleees, and some to four year colleges. Because of the large amount of laboratory work, students in this course have become very proficient in laboratory skills. To save time, students are given data sheets for recording information gathered during their experiments. Formulas for all calculations are shown on the sheets. Calculators are available in the classroom, and students quickly become adept in their use. Students are required to learn how to calculate percent composition of a mixture from data recorded in the laboratory; percent of salt in water, percent of peanut oil in peanuts; percent of water and fat in meat. Since the results of several experiments are plotted on Volume 58
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graphs, most students become reasonahly proficient with graphing techniques, as well as with reading and interpreting praphs. In all experiments requiring the recording of quantitative data. class results are oosted on the chalkboard. and class averages me calculated. Students hecome familiar with the limitations of the measured results and discuss oossible sources of error. Since the insoection of this course in 1966. enrollment has increased to a maximum of five classes with 20-24 students per class. Consistently, this has represented about one-fourth of the total enrollment in chemistry in our school. Whv have we felt it necessary and important to teach a course of this nature in our school? We live in a society that is heavily influenced by science and technology. Chemistry represents a significant part of our lives. We feel that it is important for all students to he given the opportunity to study the nature of the scientific environment that affects them. Principles studied in our course should help students to understand better many of the problems that they will face as voters and taxpayers. Some of these problems include the development of antipollution laws, construction of more efficient waste disposal ~
714
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Journal of Chemical Education
facilities, expansion or limitation of nuclear energy programs, the threat of nuclear weaoons, the oossible fluoridation of water, the location and impact of new industries on a local environment. the hetter use of foods in our elobal societv. - . and many others. Nothing.that we have done in this course has had anv adverse effect on the chemistry taught to our mare academic students. We feel a very strong responsibility for continued upgrading and improving of our offerings to these students as well. Over the oast fifteen vears. our exnerience has shown that chemistry must not be an elitist prog;am availahle only to the most academicallv"oroficient students. We have successfullv . expanded our program to include a much broader segment of our school population. We plan to continue in the same manner in the future. Literature Cited
Company, Baton. 1917.
