Richard 1. Hoffmann and Doris K. Kolb
Minois Central Colleae East Peoria, Illinois 6161 1
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An Approach to Teaching Physical Science - -
Although the course goes by various titles, many colleges offer some kind of general course in physical science designed for liberal arts majors. Students who enroll in this course usually take it only because they must, in order to fulfill a science requirement, and their attitudes toward science generally lie somewhere between indifference and repugnance. To arouse the interest of these students is the first and hardest job of the physical science instructor. At Illinois Central College we offer a year of Physical Science, which includes a one-semester survey of physics and chemistry plus a second semester of geology and astronomy. I t is the eight-week chemistry portion of the course in which we are involved, the physics and other subjects being taught by instructors in those areas. Perhaps it was an unfortunate choice of textbook that first prompted one of us (Hoffmann)to try this teaching approach. I n any case, an initial run-through of the Physical Science course using a traditional type course outline based on the textbook had proved very disappointing. Interest lagged and class attention was poor. Only during lecture demonstrations and when an occasional student was moved to ask a question were there moments of any enthusiasm. Since then the effort has been to make the students' questions an increasingly more important part of the course, until now the course is actually built around their questions.
On the first day of class students are asked to make up a list of at least six questions in the area of chemistry that they would like to have answered. They have several days to think about this. Ifleanwhile, they are given an introduction to the subject that defines what the area of chemistry is and provides a little background and some general food for thought. Those who stop by the office to complain that they "just can't think of a single question" are invited to look over the lists of questions submitted by previous classes. At the next class meeting the questions are collected and many are read aloud, the students at this time writing down any additional questions that might occur to them. From a class of 48 there will be perhaps 400 questions, some of them overlapping. The object of the course then is to find answers for as many of these questions as possible. At first it might appear that a course that uses questions from the class as its basic framework would tend to be quite different in content from one class to the next; however, this has not been the case. Although there is infinite variety in the wording of the questions, there are certain kinds of questions that will invariably be asked. For example, boys will ask questions relating to automobiles (about fuels, lubricants, antifreeze, tires, batteries, gasoline additives, enamels, etc.), while girls will ask about such things as foods, fabrics, detergents, and cosmetics. Students know from the start that all of their ques-
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t,ious cannot be anslvered in a brief eight-week introductory course but that an attempt will be made to answer most of them. As it turns out, many of their questions fall into categories of subjects that the instructor would probably have discussed anyhow. Course Summary Introduction
The course begins with a general presentation of such basic information as what chemistry is, what matter is, how compounds differ from mixtures, methods that might be used to separate simple mixtures, differences betaeen physical and chemical changes, and the fact that all matter is made up of atoms. This discussion normally precedes the collection of student questions. Atomic Structure
The first major topic taken up is atomic structure, since the answer to almost any chemical question must eventually involve atoms. Students ask a number of questions about the nature of the atom. The following are typical of the questions answered during this discussion Can an atom he weighed? If atoms are too small to see in a microscope, how do you know they redly exist? Are all atoms alike? Do scientists expect to find new elements in outer space? How can scientists tell what the sun is made of when no one has ever had a sample of the sun? I t has been said that the elements on the moon will be no different from those here on earth. How do they know this is true?
A simplified discussion of the atomic nucleus helps to supply ansn.ers for such additional questions as these What makes some racks radioactive? I have heard that the luminous dial on my watch is giving OK harmful radiation. I s this true? How can they determine haw old fossils are? What fuel does the sun use? How do atomic bombs work? What is a. cyclotron? How does a Geiger counter work? What is the difference between an A-bomb and rtn H-bomh?
Kinetic Theory
The kinetic theory provides a basis for explaining the answers to such questions as Why does water turn to steam when you heat it? Why do things become brittle when they artre extremely cold? I s i t true that heat always rises? If so, why? Can anti-freeze freeze? Why does the air get hotter when you fill up s. tire? Someone told me that windows are really liquid. How can t,hat he true? Acids and Bases
A discussion of electrolytes, including a simplified explanation of ionization, neutralization, the pH scale, and color indicators, serves to answer questions such as the following What kinds of food are acid? Why does acid eat through metal? What is AlkaSeltzer made of? What m&es the bubbles? Whv do thev add acid to swimmine noels? Why can you make some flowers change color by adding chemicals to the soil? When you rinse out s glass that had grape juice in it, why does the water turn blue? What is the most powerful acid? What is in drain cleaners and toilet bowl cleaners that makes them so dangerous?
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Oxidation and Reduction
A discussion of some simple oxidation-reduction reactions provides an introduction to the electromotive series. Oxidation and reduction are defined in terms of increase and decrease in oxidation number. Students ask a good many questions such as these Why do metals rust? How come water doesn't burn? What do they put in fire extinguishers? When a candle burns, why aren't there m y ashes? What kind of fuel do they use for rockets? Why does einc help prevent rust in an automobile fender? How is electricity stored in a car battery? Whht is a fuel cell? How do flashlight batteries work? What is the liquid that sometimes leaks out of dry cell h a 6 teries? Solubility and Solutions
Chemical Banding
The next discussion usually deals with the adhesive forces operating between atoms and between molecules. Rnoving v h y and horn atoms combine and what makes molecules stick together is an aid in understanding the ansvers to many of the questions to be considered later. An explanation as to why some atoms form ionic bonds x~hileothers form covalent bonds introduces the concept of electronegativity. Descriptions of metallic bonding and various intermolecular forces are also included. This discussion supplies answers to questions such as the follo~ving If everything is made out of atoms, what holds them together? Why do chemicals react with each other? Whs.t i.s~ snlt,? - ~ .-.
What is sugar? Why do wires conduct electricit,y but not things like wood, glass, and pla5ticP Why are some things solid and other things liquid? Why does water expand when it freezes?
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A discussion of why things dissolve and a simple treatment of the colligative properties of solutions provides answers for such questions as Why does oil float on water and not mix with it? If you spill something on your clothes, how can you figure out the best way to clean i t off? Why does snow melt when you sprinkle salt on it? How does anti-freeze keep a car radiator from freeaing? My mother uses vinegar to clean the inside of glass vases. Soap snd water won't work a t all, but vinegar does. Why is this? Periodic Toble
Some of the general relationships and property trends in the Periodic Table are presented along with miscellaneous hits of descriptive chemistry about individual elements and their compounds. The following questions are typical of the kinds of things students want to know
How do flash bulbs work? What is in photographic film that takes the picture? What are transistors made of? Why does plaster get hard when you add water to it? How does salt make water soft? Why do they put mercury in thermometers? Does gasoline really have lead in it? When a light bulb is on, why doesn't it burst from all the heat produced, and why doesn't the filament melt? What is glass made of? How can scientists tell what air is composed of? I t seems to me i t would be impossible to tell. What is the difference between ice and dry ice? What is it in exhaust fumes that causes pollution? Why do they put fluorine in water? I s i t really poisonous? How do they make fireworks? Organic Chemistry
Only a little time can be devoted to organic chemistry, but it is still possible to give the students some idea as to the almost infinite possibilities there are for compound formation among the hydrocarbons and their derivatives. Students ask many questions in this category. The following types are especially common What iis in gasoline? What is meant by the octane number of gasoline? What is nitro? I s it anything like nitroglycerine? What happens to grape juice when you make wine out of it? What is the difference between wood alcohol and ordinary alcohol? What is vinegar made of? What is aspirin made of? What is the difference between Nylon, Dacron, and polyester? Whst is Orlon? How is Teflon produced? What is TNT? What is DDT? What is LSD? What is STP? Why do they put "biodegradable" on some bottles of detergent? What is polyunsaturated fat? What is indoor-outdoor carpeting made of? How can some tanning lotions make your skin tan without the sun? What happens when milk gets sour? How do they make diet foods sweet without sugar?
Some of the students' questions are ignored became they are irrelevant or because they are merely facetious. Others are too highly complicated to be taken up in a course a t this level. Some of the questions do not'even have answers, not yet anyhow, and this is a point worth making. The fact that there are still so many frontiers to explore is one of the things that makes science so exciting. Depending on the instructor, questions such as
the following might be commented upon briefly, answered only in part, or passed over altogether Where did the earth come from? How did life get started? I s it possible to create life in a test tube? What are fingernails made of? What are the ingredients in permanent waving lotion? What is the difference between a virus and a germ? How do they make penicillin? I s cigarette smoking really dangerous? Why? Why are some people allergic to certain things? How does wlor television work? What do you need in order to make a laser? How do birth control pills work?
After all, no one can expect an eight-week course to cover everything! This question-centered course actually differs from the standard physical science course more in philosophy than in content. Much the same information is presented, but it is given largely in order to answer the students' own questions instead of simply because it happens to be in the textbook. Psychologically this makes quite an important difference in the attitude of the student, since it makes him feel personally involved in the course. The maioritv " of our Phvsical Science students are very weak in mathematics. They could not help but fare badly in an ordinary chemistry or physics course. For this reason general principles are emphasized and mathematical treatment avoided as much as possible. Examination questions usually ask for discussion of various topics, perhaps a choice of ten from a list of fifteen, and only rarely include problems. Laboratory work (2-hr/wk) is usually quantitative, but the calculations are straightforward and uncomplicated. Our Physical Science students take only eight weeks of chemistry, and this may well be their only exposure to the subject. Their whole impression of chemistry and of chemists may be based on this brief introductory course. We want to leave them with a sense of wonder instead of a sense of frustration. According to the students, they really do like this course, and they often comment on how very much they feel they have learned. As with any teaching technique, this one works best when the instructor is sold on it. Admittedly it poses a challenge for the instructor. There is more student participation in classroom discussions, and their questions sometimes require a few hours of research in the library; but the improved interest of the class is well worth the extra trouble.
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