Reviewing a high-school book in chemistry

Prentice Hall Chemistry:
Connections to Our Changing World
1996. 940 pages. ISBN of the student's edition: 0-13-828187-4.
Prentice Hall, 1 Lake Street, Upper Saddle River, New Jersey 07458.
(Prentice Hall is a part of the entertainment company Viacom Inc.)

If You Esteem "Relevance"
You Should Like This Text

Max G. Rodel

As its subtitle indicates, this is one of those textbooks that labor to be "relevant"; the writers strive to make chemistry more enticing and more accessible by linking their subject matter to ordinary life. Just why chemistry should have to be promoted in this way is puzzling. To me, this approach seems both odd and unnecessary -- much like teaching students that we value the attainments of Beethoven and Michelangelo and Victor Hugo because their art helps us learn to play our pianos, paint our ceilings, and elude the police. Chemistry, like great art, has innate beauty, and we need no other justification for studying and delighting in it.

That said, I suppose there are teachers who see "relevance" as useful or necessary in motivating students who are not distinguished by a passion for knowledge. And besides, chemistry is relevant. All physical reality consists of matter, and almost all the objects in our personal surroundings have been made or modified through the use of chemical technology.

Prentice Hall's book offers 27 chapters arranged in ten units, and the sequence of major topics is both logical and conventional. Unit 1, "The Nature of Chemistry," has a chapter on scientific methods and measurements, then a chapter that introduces some basic phenomena -- energy, temperature, matter, chemical elements, compounds and mixtures. This opening unit provides a solid foundation for the rest of the book. Unit 2 presents ideas about atomic structure and then introduces the periodic table. Unit 3, "Interactions of Matter," treats chemical formulas, bonding, molecular shapes, reactions and chemical equations.

Unit 4 is devoted to stoichiometry and the role of heat in chemical reactions. Unit 5 discusses basic properties of gases, liquids and solids. Unit 6, "Chemical Equilibrium," has chapters about solutions, equilibria and solubility. Unit 7 tells about acids, bases and buffers, while Unit 8 addresses redox chemistry and electrochemistry. Unit 9 offers a chapter about reaction rates and then a chapter about thermodynamics. The final unit, "Chemistry and Our World," is a potpourri of material about nuclear chemistry, organic compounds, and biochemistry.

Each unit begins with an eye-catching picture and a simple "Discovery Learning" activity that may help to stimulate thought. In the activity at the start of Unit 6, for example, the student sees that the temperature of an ice-and-water mixture changes when some salt is added. Why does this happen? The answer will emerge later in the unit, when the student reads about the colligative properties of solutions.

Some of those unit-opening activities, however, are unworkable. The one in Unit 5 is too vague to be performed, and the one in Unit 4 assumes that a "sample of food" -- any food -- will catch fire if the student just touches it with a burning match. That isn't true. The student may well succeed if his "sample of food" is a dry cracker, a greasy potato chip or a fatty piece of fried bacon, but he will only be frustrated if he tries to ignite a carrot, a slice of steak, a strip of raw bacon, or a piece of a chocolate bar. Have Prentice Hall's writers tried this activity?

Within each unit, each chapter has an opening page that is built around a large picture, then a "Guide for Reading" (which states some learning objectives), and then a little "Chem Journal" exercise that prompts the student to jot down some thoughts related to the subject that will be considered in the chapter. Later, after reading the body of the chapter, the student finds a laboratory experiment, a "Study Guide" that revisits important points and terms, and a "Chapter Review" that presents some short-answer questions and some problems.

The book is lavishly illustrated with photographs, charts and diagrams. Most of the illustrations are useful, but some seem superfluous and some others are liabilities. I don't think that a photograph of a chimpanzee does anything to help the student comprehend that animals exhale carbon dioxide, and I don't like the illustration on page 310, where a picture of a mole (the burrowing insectivore) introduces a chapter about "The Mole" (the chemical quantity). That is a misguided effort to be cute, and it can mislead some students.

The illustrations sometimes hinder the flow of the text or encourage the reader's eye to wander, but the book is so well organized that it does not seem disjointed. It is not nearly as garish as some of the other schoolbooks that I have seen recently.

In striving to make their chemistry "relevant," the writers have included hundreds of peripheral items that link chemistry to other sciences, to the arts, to business and industry, to environmental matters, to health, and even to domestic tasks. Some of these items appear under labels such as "Problem Solving in Chemistry," "You and Your World," "Consumer Tip" and "Careers." For the most part, they present valid and interesting information, and they usually (though not always) contribute to a lesson taught in the main text. I have noticed, however, a few items that are questionable or even incorrect, such as the unsubstantiated "Consumer Tip" about mercury in dental fillings. [See "Dangerous Blather"]

Prentice Hall's writers also have given an unusual amount of attention to historical information that illustrates the development of chemistry or provides more "relevance." For example: While many high-school chemistry textbooks have noted en passant that Lavoisier was killed by revolutionaries, Prentice Hall's book has a whole paragraph about this matter:

Tragically, Lavoisier was guillotined during the Reign of Terror that followed the French Revolution. Like many of the French nobility, he was a member of the Ferme Generale, a private company that collected taxes for the government. The Ferme Generale was a hated institution, and Lavoisier's involvement in it marked him for death. His execution was a tragedy felt in all branches of science. The mathematician Lagrange, a contemporary of Lavoisier's, said: "It took them only an instant to cut off that head, and a hundred years may not produce another like it." [page 73]

In sum, Prentice Hall Chemistry: Connections to Our Changing World is a good text. Its intimidating length and occasional failures notwithstanding, it should be a sound choice for chemistry teachers who want to emphasize how chemistry "connects" to the everyday world. I recommend it.

Contrived "Connections"
and Needless Difficulties

Narcinda R. Lerner

The book's ten units cover the usual subjects, and the order of presentation is standard. The only unit that is somewhat unconventional is the final one. Prentice Hall's writers have dumped organic chemistry and nuclear chemistry into the book's concluding chapters, as tradition dictates, but they also have added a chapter (titled "The Chemistry of Life") that surveys some topics in biochemistry. This is unusual but not unique; a comparable chapter, sporting the same title, concludes the 1993 version of Heath Chemistry.

As is the case with most high-school books nowadays, this one is oversupplied with illustrations, many of which are irrelevant or even erroneous. This is not a trivial consideration, because superfluous illustrations add to both the cost and the weight of a textbook. (I own an introductory college textbook of chemistry, published some 40 years ago, that weighs about 1 kg. Prentice Hall Chemistry: Connections to Our Changing World weighs twice as much, and I am sure that superfluous pictures account for much of the increment.) If Prentice Hall were to sponsor an award for needless and foolish illustrations, my nominees would be:

• Figure 8-3, comprising a picture of some pyramids in Egypt, a smaller picture showing a ball-and-stick model of ammonia, and this caption: "Chemists use ball-and-stick models (right) to indicate molecular shape. A molecule of ammonia has the shape of a pyramid with a triangular base, similar to the pyramids of Egypt (left)." This exhibition is not only gratuitous; it is dead wrong. The Egyptian pyramids have square bases. They aren't tetrahedrons, and they aren't "similar" to a tetrahedral molecule of ammonia.

• The frontispiece for chapter 15, comprising a big photo of the Grand Canal, an inset picture of an eagle, and this caption: "Gondolas float on a saltwater solution along the liquid `streets' in Venice, Italy. An eagle, meanwhile, soars majestically, through a solution of air in the skies above Alaska." A solution of air? In what? The air above Alaska is itself a solution of oxygen and other gases in nitrogen, but the air is not dissolved in anything. And anyone who has visited Venice knows that the liquid in Venetian canals is not a solution but an aqueous suspension, loaded with visible particles of solid materials. Prentice Hall's pictures are not only needless but misleading as well: a poor way to start a chapter that will try to tell what solutions are and how they differ from heterogeneous mixtures.

• Figure 15-2 -- a picture of a random assortment of unidentified pills, accompanied by a caption saying: "Some vitamins, such as A, D, E, and K, are soluble in fat. Others, such as vitamins B₂ and B₁₂, are soluble in water. Which type of vitamins do you think accumulate in the body and which type are eliminated in the urine?" I assume that the pills are supposed to contain vitamins, but there is no way to tell which pills contain which vitamins, and nothing shown in the picture has anything to do with solubility.

• The frontispiece for chapter 18, comprising a photo of a marine bird, a smaller photo of an antacid tablet dissolving in water, and this caption: "The giant petrel -- also called the 'stinkpot' bird -- spits stomach acid at its enemies. To neutralize excess acid in your stomach, you might take an antacid tablet (inset)." What is this supposed to signify? Do petrels suffer from "excess acid"? Does Prentice Hall plan to supply Alka-Seltzer to the petrels' enemies, so the enemies can prevail and can rid the world of stinkpots?

A photograph in chapter 13 deserves special attention because it not only is irrelevant to the text but is positively dangerous. Though chapter 13 deals with gases, figure 13-10 shows a woman who is pouring some sort of liquid into a graduated cylinder; and though her eyes are completely unprotected, the caption says: "Chemistry is an experimental science. . . . Remember that you should always wear safety goggles in the laboratory." Obviously, Prentice Hall's editors recognized that their picture was defective and would set a dangerous example. But instead of replacing it, they have tried to get away with tacking a lame disclaimer onto the caption. This is unacceptable.

On the other hand, the book does provide portraits of many noteworthy chemists, with captions that tell about their achievements. This is commendable because it reminds students that chemistry is the work of real people, and that progress in chemistry reflects the insights and efforts of inspired individuals.

• In section 17-1, titled "Solubility Equilibria," the writers say: "If you have ever had a cavity in your tooth drilled, you have already had a painful lesson about the solubility of solid substances." But dental drilling has nothing to do with solubility, and (if the dentist administers a local anaesthetic) it need not cause pain.

• On page 504 the student is told to solve a "problem" that isn't a problem at all. The writers apparently were desperate to invent a "connection" out of nothing:

  Your neighbor has gone on vacation for a week and has asked you to take care of her aquarium. The aquarium is filled with water and contains a few fishes and plants. Unfortunately, your neighbor forgot to tell you whether the water is fresh water or salt water and you need to know before adding any more water. You cannot analyze the water by smell and you certainly do not want to taste the water! Devise a method of determining which type of water is in the aquarium using only materials available in the kitchen.

  The adjacent illustration shows a girl who is peering into an aquarium and who supposedly can't tell whether it holds fresh water or seawater. In fact, the answer does not matter. Even if it is a seawater aquarium, the girl should add water that is fresh. (A seawater aquarium loses water by evaporation, but it doesn't lose salt. The quantity of salt in the aquarium stays constant, so an aquarist needs only to add plain water, from time to time, to keep the salt at a proper concentration. If the aquarist were to compensate for evaporation by adding seawater, the concentration of salt would continually increase and would soon become lethal to the aquarium's inhabitants.) In passing, let us note that Prentice Hall's writers are being silly when they say, "you certainly do not want to taste the water!" Why not? Hobbyists (and scientists, too) often taste the water in aquariums (or the water in rivers, marshes, pools or estuaries) to get an idea of how salty it is. Maybe the writers are trying to reinforce the notion that girls are hopelessly squeamish.

• In section 12-3, the discussion of Hess's law -- a thermodynamic concept which applies to all sequences of chemical reactions -- is built around a sequence of reactions that lead to the production of NO₂, one of the principal components of smog. But the role of NO₂ in smog is so overemphasized that the student may well infer that the purpose of this discussion is to tell about air pollution, rather than thermodynamics.

Indeed, this textbook is particularly obscure whenever it discusses thermodynamics, and the section about equilibrium constants in particularly misleading. On page 542, for example, the writers say that "Units are customarily omitted from the equilibrium constant." They do not explain that, for most chemical reactions, the numerical value of an equilibrium constant depends upon the units in which concentrations are expressed. The student does not learn the essential fact that the value of an equilibrium constant will change if concentrations are given in atmospheres rather than in moles/liter.

The section about the enthalpy changes that accompany chemical reactions is poorly written and difficult to follow, made all the worse by statements like this one: "[A]n important condition for the reaction is that the reactants and products are [sic] in their standard states." The student, no doubt, will interpret this to mean that a reaction will proceed only under standard conditions. Not until later do the writers manage to say what they mean.

In the chapter about "The Chemistry of Life," the section on nucleic acids is totally incomprehensible. This is a shame because the student's knowledge of chemistry should now be sufficient to enable him to understand, on an elementary level, how DNA and RNA operate. But all that the student gets here is a string of incomprehensible sentences like these: "Each of the strands in the double helix is composed of nucleotides attached by covalent bonds. The two strands are aligned in an antiparallel arrangement (facing in opposite directions). These antiparallel strands are attached to each other by numerous intermolecular hydrogen bonds. The . . . hydrogen bonds cause the double strand to twist into a helical shape."

There is no diagram to show how the nucleotides are attached to each other, or to show what "antiparallel" means, or to explain the crucial concept of base pairing. A few carefully done diagrams would have given meaning to the writers' empty prose. Why have such necessary illustrations been omitted from a textbook that is so copiously loaded with illustrations that are irrelevant and useless?

I don't recommend Prentice Hall Chemistry: Connections to Our Changing World. I believe that most high-school students would find that this text presents needless and frustrating difficulties.

Max G. Rodel is a consulting environmental chemist and a registered environmental assessor in state of California. His major professional interest is the chemistry of natural aquatic systems, including the fates of pollutants. He lives and works in Mill Valley, and he regularly reviews science textbooks for The Textbook Letter.

Narcinda R. Lerner is a research chemist. She works at the National Aeronautics and Space Administration's Ames Research Center (at Moffett Field, California). Her professional interests include polymer chemistry and the origin of organic materials in meteorites.

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