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

I Weep for the Students

Lawrence S. Lerner

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:

• On page 12 we read a false account of Benjamin Thompson, Count Rumford. Some of the falsity is in the student's text, some in a pedagogic note. We read that Thompson was born "in New Hampshire." (No, he was born in Woburn, Massachusetts.) We read that he "fought on both sides of the American Revolutionary War." (No, he was a loyalist, but there were unsupported accusations that he worked as a double agent). We read that he "moved to England after the American Revolution." (No, he went to England with British forces who left Boston in March 1776.) We read that he "became known [in England] as Count Rumford." (No, he really became Count Rumford, a count of the Holy Roman Empire. And he got that title only after he had worked for many years in Bavaria.) We read that he supervised the making of cannon in Bavaria and in England. (No, only in Bavaria.) We read that he "noticed that when holes were drilled in cannon barrels, the barrels and the drills became hot" (So what? People had been noticing this for centuries. It was common knowledge.)

• Page 13 tells that James Prescott Joule "investigated the relationship between heat and motion" and "performed a series of experiments," but the experiments aren't described. What did Joule do that Rumford hadn't already done? (Page 18 offers this pedagogic note: "Rumford: Heat is not a substance (caloric); it involves motion. Joule: Heat is a form of energy involving motion." Well, that certainly clears things up!)

• On pages 14, 16 and 17, illustrations purport to show how heat is transferred, at the molecular level, by conduction, convection and radiation. The illustrations and their captions are wrong or (at best) quite incomprehensible. The caption on page 14, for example, says: "As fast-moving warmer molecules collide with slow-moving cooler molecules, heat energy is transferred . . . ." That is all wrong because the concept of heat simply does not apply at the molecular level. Heat is a large-scale, macroscopic phenomenon. The notion of hot molecules (or "warmer molecules" or "cooler molecules") is nonsensical.

• On page 15, the text proffers more nonsense: "When fast-moving molecules collide with slow-moving molecules, heat energy is transferred . . . . causing the slower molecules to move faster. Now these molecules have enough energy to collide with other slow-moving molecules." Didn't they have enough energy to collide before? Why not?

• Page 17: The writers say, mysteriously, that convection currents form in the oceans "as warm water rises to the surface and cold water sinks to the bottom." They don't suggest why there would be warm water in the oceans' depths. Are there huge hot-plates down there?

• Page 19: The caption for figure 1-9 asks, "How does Old Faithful geyser . . . illustrate the relationship between heat and temperature?" Here is the "answer" furnished in a note to the teacher: "heat energy increases the average kinetic energy, which causes a rise in temperature." Another note tells the teacher to ask students why Old Faithful "erupts so violently." The note then advises: "Accept all logical answers. Students may suggest that molecules are heated in water." (As beans are boiled for dinner?) Finally, the teacher must ask the students why Old Faithful "erupts on an irregular schedule." The writers' "answer" does nothing to explain why the intervals between successive eruptions may (or may not) be irregular.

• Page 20: The "Find Out by Doing" item is imaginary science. It is a fake experiment that won't work, and I must wonder whether the writers have ever tried to perform it. The student puts a drop of food dye into a beaker of cold water, puts another drop into a beaker of water that is at room temperature, and watches for changes "related to the effect of heat on the motion of molecules." The writers guess that the dye will disperse more rapidly in room-temperature water, but the experiment will fail for two reasons. First, dispersion of the dye (in both beakers) will be dominated not by diffusion but by turbulence created during the filling of the beakers -- and such turbulence will persist for hours or even for days. Second, a diffusion rate is proportional to the square root of the absolute temperature. If, for example, the temperatures of the two masses of water were 20 degrees C and 7 degrees C (i.e., 293 and 280 kelvins), diffusion in the warm water would be only 2% faster than in the cold water. This small difference couldn't be detected in Prentice Hall's "experiment."

• Page 24: In the "Content Development" note for the teacher, the description of specific heat is all wrong because the writers repeatedly confuse specific heat with heat capacity. The "Guided Practice" note, too, is all wrong -- for the same reason.

• Page 24: An "Ecology Note" to the teacher says that a heat pump is "like a refrigerator in reverse." Wrong. A heat pump is a kind of refrigerator, and there is no "reverse" about it. The writers evidently have heard that a heat pump is a heat engine running in reverse (which is true) but have failed to grasp what that means. Not surprisingly, their text about heat pumps (on page 46) is woefully wrong, though their explanation of refrigerators (on page 52) is correct.

• Page 27: A "Find Out by Calculating" exercise asks the student to find the energy content of one serving of yogurt or peanut butter. A note to the teacher provides a sample calculation for peanut butter, then concludes: "The total is . . . 205 Calories. This is a little bit higher than the number -- 109 Calories -- given on the label." A little bit higher? The discrepancy is nearly 100%. Why haven't the writers accounted for it? Do they really think we can't see that something is seriously wrong here?

• Page 28 offers fakery in boldface type: "What causes a phase change? A change in phase requires a change in heat energy." But the question was: What causes a phase change? The text provides no answer. (And by the way: Just what is "a change in heat energy"?)

• Page 33: The writers say that water furnishes the "one exception" to the rule that liquids expand when they are heated but contract when they freeze. Not so. Bismuth and antimony also expand when they freeze, as do some alloys that contain those metals. This is why bismuth and antimony are used in type-metal, which can be molded with great accuracy: The metal does not shrink as it solidifies, so it does not pull away from the corners and edges of the mold.

• Page 34: A note tells the teacher why an ice tray should not be filled to the brim with water before it is put into a freezer: "The water will expand and might crack the tray." Of course, this is false. The ice tray is open at the top, so there is plenty of room for expansion.

• On the same page, another note tells the teacher why one should not heat food in a closed container: "The gas will expand rapidly and might cause an explosion." Here "the gas" presumably means the air that was in the container to begin with, as well as the water vapor that evolves from the food during heating. In any case, the writers' answer is completely wrong. If the container is closed, the gas can't "expand" at all -- its volume must stay constant. As a result, the pressure in the container rises, and this increase in pressure can cause the container to burst. The writers have shown that they don't understand the gas laws. (They do this again when they try to discuss the gasoline engine. They again confuse pressure and volume.)

• Page 37 has a summary of the "Key Concepts" in chapter 1. Among them are: "Heat is a form of energy related to the motion of molecules" and "The ability of a substance to absorb heat energy is called its specific heat" and "Thermal expansion . . . can be explained in terms of the kinetic energy of molecules." Those first two statements make no sense at all, and the third is true for gases only.

• Page 42 has a picture of a "modern building heated entirely by the heat given off by computers." Nonsense. In buildings that rely wholly or largely on the heat evolved by electrical equipment, most of the heat comes from lights and motors, not from computers.

• Pages 43 through 45 show six common house-heating systems. There are serious errors in the "Steam Heating" diagram, in both diagrams that purport to show radiant heating, and in the ones titled "Warm-Air Heating" and "Heat Pump."

• Page 51 offers more imaginary science. The writers evidently have heard that a white object reflects radiation more effectively than a dark object does, so they lead the student to believe that this is why pizza boxes are white instead of brown. Pure nonsense. For a pizza in a box, the loss of heat by radiation is negligible when compared with the loss by convection. Pizza boxes are made of white cardboard for cosmetic reasons.

• Page 54: Here he is again! -- old Elijah McCoy, the black inventor that we encountered in Motion, Forces, and Energy, another of Prentice Hall's books. (See "The Fake McCoy" in TTL, November-December 1992.) In a "Multicultural Opportunity" note to the teacher, Prentice Hall's writers again credit him, falsely, with inventing drip lubrication. Indeed, they cast him as the first person to think of a "procedure for the automatic lubrication of machinery"! His birthdate, however, has moved from 1884 to 1844.

• Page 54: The first sketch of a steam engine is correct. The second, showing the return stroke, has the inlet valve in such a position that steam can't enter the cylinder.

• Page 58: A caption says, "These cooling towers at a nuclear-power plant are used to reduce thermal pollution." Not true. The towers expel waste heat into the environment, but they don't "reduce" the amount of heat that is expelled. The use of cooling towers merely means that heat is discarded into the air, rather than into a river (for example).

• Page 62: Under "Concept Mastery," the student finds a nonsensical, unanswerable question: Which body of water -- an ocean, a river or a lake -- would be most affected, or least affected, by thermal pollution from a factory? The absurd "answer" given to the teacher includes this: "Because rivers are constantly moving, the water would not greatly increase in temperature because the thermal pollution would be passed through out the river." That makes no sense, and it deflects attention from the fact that thermal pollution regularly damages rivers in the real world.

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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