edited by J. DUDLEY HERRON Purdue University West Lalayette, Indiana 47907
Hey, Watch Your Language! J. Dudley Herron
Purdue University West Lafayette, Indiana 47907 I was struck by a comment in a review of Buckminster Fuller's latest hook, "Synergetics: Explorations in the Geometry of Thinking." Fuller, it seems, would like to see us talk about "sunsight" and "sunclipse" instead of sunrise and sunset, the latter words being based on a geocentric view of the universe even thoueh the heliocentric view has prevailed for centuries. I doubt that the terms will change, hut'tlw point is well takrn. Words are the s t u t i t h i ~ ~houcht; t are made ut. We need to watch what we say and how wesay it. Teachers are often careless with words and we pav the price in terms of contused ideas and time spent in ..unle&nina."l'he followine:examples from mv obser\,atims in high . SI h m l i illustratemy point. The lesson started with a dipping contest. One student was nsked to dip punch with a small dipper and pour it into an adjacent howl while an opponent reversed the flow of liquid by dipping with a larger dipper. A reasonable facsimile of a iynamic equilihrium was soon established as the level in one bowl was lowered to the point that the large dipper was transferring the same amount of liquid as the filled, smaller iipper. T o describe the dynamic equilihrium, the teacher ?xplained, "Notice that we have two opposingforces in balance." He was using "force" as it is often used in common speech and i t got him into trouble. Moments later, he cited an :xample of a tug of war in which opposing teams are equally natched so that there is no movement and asked, "Is this an ?xample of dynamic or static equilibrium?" The entire class ndicated that it was dvnamic and no wonder: he had deicribed a situation in whirh thrnt wcre"two ~~pposing forces n t~nlance." He was unable to extricate himself from the :onfusion by the end of the hour, an hour wasted because of iloppy language. Shortly after this incident, I witnessed a demonstration of ;he hlue hottle system.' After shaking the bottle to produce ;he hlue color, the class watched as the color faded-and lis;ened to the teacher remark, "Did you see the solution clear lp?" Of course they had and the teacher innocently reinforced I point of confusion likely to cause trouble later on. Surely the .eader has shared mv of havine" heeinnine students - experience . :onfuse color change with formation or disappearance of a x e c i ~ i t a t eThe . instructions in the lab manual sav somethine ike, "dd HCI until the solution becomes clear." After adding :opious volumes of acid the student brings the hlue solution )f copper (11) chloride and asks, "What's wrong? I can't get ny solution to clear up." Clear and colorless do not mean the ;ame and the distinction is important in many observations. :f we do not use words with care, we introduce and reinforce :onfusion. One day later I visited a class in which the concept of acid was discussed. The teacher had written an eouation to illusr a t e the dissociation of HCI in solution to foim H + and Cl-. He followed quicklv with acetic acid and asked. "What will ,e produced when the acid dissociates?" " ~ y d r & e nand ac330 / Journal of Chemical Education
etate," was the prompt reply and the lesson continued u,ith another example. It shouldn't have. Hydrogen is not produred when an acid disst~ciate;nnd we must n d ilssume thnt the student knows and means. "hydrogen ions." Heginn~t~g students often w e no diffrrenrr in H'. H. and H,e w n thoueh " they represent distinctly different entities. If we are careless in accepting "hydrogen" as a satisfactory name for H+, we perpetuate this confusion. Not only must we be precise in our own lanauaee, we must insist that the student do the same. Not ail language problems are as simple as the ones given above. Take my statement concerning the "dissociatlon of HCI," for example. Is this correct? Does the HCI dissociate or does it ionize? What about acetic acid in water? or NaCI? As we view ionic solids, we assume that they are already composed of ions-a reasonable approximation in most cases. When NaCl dissolves, it is reasonahle to assume that ionization has already occurred and the process is essentially one of dissociation:. i.e... comine..anart. . But HC1 is eenerallv viewed as a cuvalent molecule which I'orms ions m l y m thr presenrr of a polar solvent. When dissol\,ed in water, it dissucinte,. 1.e.. comks apart and ionizes; i.e., forms ions. The danger is that we lead students to confuse two processes: one heine the "coming npnrf" of R ~ I I I ~ C U I P the , other hein!: t he formiltwn of particles w ~ t han excess or d e f i ~ ~ m cofyelectron.;.' That both processes may occur simultaneously should not lead to the mistaken notions that processes are identical or that they always occur in concert. For example, we talk about dissociation energy associated with Hp, 2H(,, and ionization energy associated with NaW Na (g, le-; the first involves dissociation hut no ionizat~onwhile the reverse is true of the second. Some terms have become so confused in usage that it is extremelv difficult to induce claritv in the minds of theheginning (& even advanced) student.~alenceis a case in point. Standard texts commonly u5e valence in reference to quite different, although related, ideas. Early in the course it is common practice to use valence in reference to the comhining numher of an element; for example, "In water oxygen has a valence of two; it combines with two hydrogen atoms." Later, valence is often used in reference to oxidation number. as in the statement, "Sulfur has a valence of plus six in sulfuric acid." In another context we speak of the numher of valence electrons (which is frequently not the same as the comhining numher or oxidation number) and discuss the valence shell of an atom. After years of experience, the chemist has little difficulty in inferring the proper meaning of valence from the context in which it is-used, hut the heginhng student does not have the benefit of such experience and needless confusion
- -+
1 For those unfamiliar with the system, it is prepared as follows: "A one liter flask is half filled with water, and 10g of sodium hydroxide are dissolved in it. Ten g of dextrose (glucose) are then added and allowed to dissolve. About one ml of a 1percent solution of rnethylene blue in ethyl alcohol is then added. Upon Standing in a stoppered flask, the resulting solution becomes colorless." [From Camphell, d. A. "Why Do Chemical Reactions Occur?", Prentice Hall, Englewuod Cliffs, N.J.: 1965.1 For more information on this particular issue see Herron, J. D., J. CHEM. EDUC., 54, 758 (1977) and Herron, J. D., J. CHEM. EDUC., 55,393 (1978).
results from careless and imprecise usage. Although it is impossible for a single teacher to insulate students from such multiple uses of a common term, it is possible to point out that the term is used with these different meanings and to limit one's own use of the term to a single meaning or to emphasize the exact meaning within the context in which it is used. Some may argue that I carry things too far when I implore that we not say, "Write the reaction that occurs when you add an acid to a base," hut I consider this language improper. Reactions appear in test tubes, beakers, and living organisms; equations appear on paper. One cannot write a reaction, only an equation. It is an important distinction because heginning students come to believe that what is seen in symbolic language on the chalkboard or printed in the text is the reaction. They need tosee that it is merely an attempt todescrihe (often in very simplified form) what we believe is happening in a chemical system, what we propose might happen under given
conditions, or even what we believe will never happen. We write equations for reactions that do not occur and many reactions occur for which we cannot write an equation. We need to keep things straight. Although much of our imprecision with words can he attributed solely to carelessness, some results from our own confusion and lack of understanding. Take the case of electronegativity. Most of us discuss the electronegativity of an element as though it were something real and fixed. For some this is careless simplification for they know that the electronegativity of chlorine is not the same when hound to carbon in CC4 as when hound to oxygen in C104- and that discussion of the electronegativity of an isolated atom is meaningless. But for more, the concept is just not clear. This language problem can he solved only when we are all willing to expose our ignorance to our colleagues and peers in the belief that, together, we can grow in our own understanding and "watch our language" because we know what is means.
Volume 56. Number 5, May 1979
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