from The Textbook Letter, January-February 1993

Reviewing a middle-school book in the Prentice Hall Science series

Heat Energy
1993. 80 pages. ISBN of the teacher's edition: 0-13-980004-2.
Prentice Hall, 113 Sylvan Avenue, Englewood Cliffs, New Jersey 07632.
(Prentice Hall is division of Simon & Schuster.)

I Weep for the Students

Lawrence S. Lerner

Prentice Hall's Heat Energy consists of an introductory spread, two chapters of text (titled "What Is Heat?" and "Uses of Heat"), three "Science Gazette" features, and some appendices. The whole structure, including the pedagogic material in the teacher's edition, is permeated by misconception, misinformation and gross ignorance. The writers just don't know what they are writing about.

The introductory spread (on pages 8 and 9) merits close attention. Page 8 shows a barely recognizable thermogram of a girl and her dog, and the text says: "In this thermogram, the hottest areas are red and the coolest areas are blue." Page 9 shows a color photograph of burning coal, with this caption: "Burning coals glow reddish yellow. As in a thermogram, the hottest coals appear red and the coolest appear blue [emphasis added]." A note to the teacher reinforces the idea that colors in a thermogram correspond to colors in the real world: The writers ask the teacher, "How are the thermogram picture and the picture of the burning coals alike?" And then they answer: "Both show heat through color. The same colors show more intense and less intense amounts of heat."

What a rich texture of ignorance! First, the writers don't grasp that a thermogram is a false-color image, made by a computer that has been programmed to assign arbitrarily chosen colors to various wavelength distributions of invisible radiation. The distributions represent various temperatures on the surface of the object that the thermogram depicts. The colors red and blue are customarily chosen to represent the highest and the lowest temperatures, but a computer can just as easily be programmed to use some different scheme -- say, blue for the highest temperatures and green or yellow for the lowest.

Obviously, then, the writers' attempt to compare the thermogram to the photograph of burning coal is ridiculous. In the photo, made with visible light, the hottest areas are white, cooler areas are yellow, still cooler areas are red, and the coolest are black. The red-through-blue sequence imagined by the writers is simply not there! Further, the writers do not grasp that a pile of coals crudely approximates a blackbody radiator. To emit blue light, such a radiator must attain temperatures so high that they rarely, if ever, occur in a convective coal-air fire.

The note to the teacher is doubly absurd. Besides repeating the fantasy about colors, the writers speak of "more intense and less intense amounts of heat," a phrase that has no meaning in physics or even in ordinary English. What in the world is an "intense amount"?

One reason why the writers utter such gobbledygook becomes obvious in the "Discovery Activity" on page 9, which shows that the writers don't know the difference between heat and temperature. The activity involves bowls of cold, lukewarm and hot water. The student places one hand in the hot water, the other hand in the cold water. Then, after a while, he immerses both hands in the lukewarm water and presumably notes that this water feels hot to the cold hand but cool to the warm hand. Then he must answer questions: "Is using your hands a good way to measure heat? Could a scientist measure heat in this way? What does this experiment tell you about the relationship between heat and temperature?" At the bottom of the page, an instruction for the teacher says, "[S]tudents will note that touch is an inaccurate way of measuring heat. . . . Students should conclude that although there is a relationship between heat and temperature, they are different."

In fact, the activity has nothing to do with measuring heat, tells nothing about either heat or temperature, and certainly doesn't tell how heat and temperature may be related! Further, the repeated reference to measuring "heat," though the receptors in the student's hand are actually responding to changes in temperature, shows that these writers can't tell one phenomenon from the other.

Maybe you think that I have unfairly picked out the worst pair of pages in the book. Not so. For another pair that shows a comparable congeries of nonsense, look at pages 30 and 3l:

On page 30, in an exercise, the student must identify "Substance X" after reading of how a given mass of the substance responds to successive additions of heat. The "answer" given to the teacher is wrong.

On the same page, a graph wrongly shows the heat capacity of steam to be considerably greater than that of liquid water.

On the same page, a note to the teacher says, "Latent heat is involved in both fusion and vaporization as long as these transformations are isothermal; that is, taking place at a constant temperature." Meaningless.

On page 31 the violent fizzing that occurs when a warm bottle of soda is opened is wrongly attributed to thermal expansion. (The right explanation: As temperature increases, the solubility of gases decreases.)

On the same page, a "Multicultural Opportunity" note to the teacher says: "Ask students to identify examples of thermal expansion. These might be devices (like the thermostat) or examples of expansion (such as cracks in the sidewalk or potholes)." Just how is that supposed to expand our "multicultural" perspective? Is there some culture in which thermal expansion works in ways unknown to us?

On the same page, the teacher finds an "ESL Strategy." Students are to indicate which of several phenomena can exemplify thermal expansion. The first phenomenon is "A water pipe freezes," which the writers dispatch with this remark: "Not an example. When the ice thaws, the water will contract rather than expand." Yes, but it certainly expanded during freezing, and the freezing of water does exemplify thermal expansion. Moreover, I fail to grasp how the writers' faulty logic can help anyone learn English.

Now, a sampling of some other pages:

The "Science Gazette" features (starting on page 65) contain plenty of nonsense, and the writers use empty, tinny phrases that recall consumer-product advertising. They say, for example, that a microbiologist employs a mysterious "special machine" and "powerful chemicals," while a heating system uses "special calcium compounds" that are "amazing."

What really is amazing is this book's glossary. Of its 45 entries, at least 18 are wrong, misleading or tautological.

I close by returning to page 39, where an exercise asks the student to try his hand at haiku, a form of Japanese poetry in which each poem has seventeen syllables: five in the first line, seven in the second, five in the third. Inspired by what I have seen, and knowing how this book will destroy young people's innate scientific insights and innate interest in nature, I have written a haiku of my own:

I weep; students read
Prentice Hall's Heat Energy
And unlearn Science.

Lawrence S. Lerner is a professor in the Department of Physics and Astronomy at California State University, Long Beach. His specialties are condensed-matter physics, the history of science, and science education.


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