Reviewing a middle-school book in physical science

Prentice Hall Exploring Physical Science
1999. 818 pages. ISBN of the student's edition: 0-13-435873-2. Prentice Hall.
(Prentice Hall is a part of Pearson Education, 1 Lake Street, Upper Saddle River,
New Jersey 07458. Pearson Education is a division of Pearson PLC, a British
corporation headquartered in London.)

This Prentice Hall Book Fails on Each and Every Count

Leonard Tramiel

When Lawrence S. Lerner reviewed the 1995 version for The Textbook Letter, he described many of its defects, he said that educators "should avoid it like the plague," and he showed that Prentice Hall's editors, at the time when the book was printed, knew that it contained erroneous material [see note 1, below].

More recently, the 1995 Exploring Physical Science has been exposed in the popular media -- first in a long article published by The [Baltimore] Sun, then in a long segment of the ABC television network's program 20/20. The 20/20 segment included an interview in which Anthea Maton, the woman whom Prentice Hall had alleged to be the primary author of Exploring Physical Science, said that she had never even seen Exploring Physical Science until the interviewer showed it to her [note 2].

Prentice Hall is now a part of Pearson Education, and Pearson is now selling a version of Exploring Physical Science dated in 1999. The 1999 is the version that I am reviewing here, and I will give you my overall conclusions right now: Though Prentice Hall's editors have had ample opportunity to fix Exploring Physical Science, they haven't done this. The 1999 version, like the 1995, is so bad that it could serve as the poster-book for a campaign to undermine the teaching of science in our schools.

Glancing at the title page of the 1999 version, we once again see Prentice Hall's claim that the chief author of Exploring Physical Science is Anthea Maton. This claim, as we know, is false.

Looking at the book's table of contents, we see that Exploring Physical Science has six units: "Matter: Building Block of the Universe," "Chemistry of Matter," "Motion, Forces, and Energy," "Heat Energy," "Electricity and Magnetism" and "Sound and Light." Not coincidentally, those are the titles of six books in the Prentice Hall Science series, which Prentice Hall has sold for years [note 3]. Prentice Hall produced Exploring Physical Science by combining old material from those six earlier books -- in fact, Exploring Physical Science consists essentially of those six books bound together.

Remembering that Exploring Physical Science is a composite of six earlier books, we might expect the content of Exploring Physical Science to be disjointed. It is, but this is just one of the reasons why Exploring Physical Science is unacceptable. Even within the six constituent books, the material is poorly conceived and poorly organized -- paragraphs don't hold together, the sequence of topics is often arbitrary and unworkable, the writers ignore connections that would help students to see how different topics are related, and there are mistakes of every variety, from simple typographical errors to major factual and conceptual blunders which show that Prentice Hall's writers and editors don't know the material.

Chapter 1 of Exploring Physical Science is called "Exploring Physical Science" and purports to be an overview of science and of what scientists do. After announcing that "The goal of science is to understand the world around us," the writers try to introduce the concept of a scientific theory. They begin by presenting (at the top of page 8) an old illustration which has appeared in a number of Prentice Hall books, over the years, and which comprises a pair of photographs plus this caption:

It had long been a theory that a liquid did not retain its shape when removed from its container. However, scientists were forced to change that theory after observing the photographs shown here. The photographs show that the water in the balloon retained its balloon shape for 12 to 13 millionths of a second after the balloon had been burst by a dart.

What nonsense! As I have explained in an earlier issue of The Textbook Letter, the notions conveyed in that caption are so entirely divorced from reality that the caption isn't even wrong -- it is absurd. Scientists have never held any "theory" about the shape of a liquid, the photographs don't show anything that was unexpected, and the photographs haven't forced anyone to change anything [note 4].

Below the water-balloon illustration the Prentice Hall writers begin a three-paragraph passage that supposedly tells about how scientific theories are constructed. This material is so tangled and so rife with distortions and inaccuracies that it deserves to be quoted and then analyzed, as another example of what happens when "science" books are written by people who don't know science. Here is the passage:

After studying facts, making observations, and performing experiments, scientists may develop a theory. A theory is the most logical explanation for events that occur in nature. Keep in mind that scientists do not use the word theory as you do. For example, you may have a theory about why your favorite soccer team is not winning. Your theory may or may not make sense. But it is not a scientific theory. A scientific theory is not just a guess or a hunch. A scientific theory is a powerful, time-tested concept that makes useful and dependable predictions about the natural world.

When a scientist proposes a theory, that theory must be tested over and over again. If it survives the tests, the theory may be accepted by the scientific community. However, theories can be wrong and may be changed after additional tests and/or observations.

In some cases, if a hypothesis [sic] survives many tests, it becomes a law. A law summarizes observed experimental facts -- it does not explain the facts. The explanation resides in the appropriate theory. Laws, like theories, may change as new information is provided or new experiments are performed. This points out the spirit at the heart of science: Always allow questions to be asked and new scientific explanations to be considered.

Now let me give some analysis of that material, starting with the writers' attempt to define a theory as "the most logical explanation for events that occur in nature." The phrase "most logical" is another piece of nonsense. The word logical (like the word unique or the word absent) has no comparative or superlative. A given argument either is or isn't logical. If the argument complies with the canons of logic, then it is logical -- and if it doesn't comply, then it isn't. All arguments that comply with the canons are fully and equally logical, and none of those arguments is any more logical, or less logical, than any of the others.

When these Prentice Hall writers define "theory" as "the most logical explanation for events," they imply that there can be only one theory to explain a given set of events. That is false. For a given set of events, we may have multiple explanations that are logical and that are quite compatible with our observations.

The matter of observations leads us to the third mistake in the writers' definition of "theory." The writers have completely failed to apprehend that a theory not only must be logical but also must be consistent with what we observe. In other words, the writers have forgotten their own declaration that science deals with "the world around us." No argument, even though it may be logical, can qualify as a theory if it fails to take account of what we see, or don't see, in the real world. No argument, even though it may be logical, can qualify as a theory if it is based upon assumptions, premises or "facts" that deny observed reality.

After failing to explain the concept of a scientific theory, the writers gratuitously disparage and discourage the student:

Keep in mind that scientists do not use the word theory as you do. For example, you may have a theory about why your favorite soccer team is not winning. Your theory may or may not make sense. But it is not a scientific theory. A scientific theory is not just a guess or a hunch.

How do the writers know how the student uses the word theory? Why do the writers contrive an irrelevant, misleading example that deals with soccer scores, instead of using an example that involves some phenomenon of nature? And why do they say that the student is incapable of conceiving a scientific theory and is incapable of formulating anything beyond "a guess or a hunch"? Anyone may come up with a scientific theory. A student may, for example, come up with an explanation for some kind of behavior exhibited by the birds that visit his yard. His idea probably won't carry the profound implications that we associate with theories conceived by Nobel laureates, but if his explanation is logical and is consistent with repeated observations, then it will qualify as a scientific theory.

At the start of the third paragraph, the writers introduce the term "hypothesis" without any definition or explanation. Where did this come from? The preceding paragraph dealt with the testing of "a theory," but now the item that is being tested is "a hypothesis." How is a hypothesis related to a theory? Are a hypothesis and a theory the same thing? Students who wonder about this must continue to wonder until they reach page 12, where the writers will disclose that "A proposed solution to a scientific problem is called a hypothesis (high-PAHTH-uh-sihs)," and that a hypothesis must be tested to show whether or not it is right -- which is much the same as what they wrote, on page 8, about a theory. Students can't be blamed if they infer that the terms hypothesis and theory are interchangeable.

The writers' puzzling use of the word hypothesis is overshadowed, however, by their mauling of the term law and their attempt to draw a functional distinction between a law and a theory. That attempt is still another piece of nonsense.

In science, the term law is commonly used in two ways and has two different meanings. First, law may mean a rule which matches observations but has no theoretical basis. (An example is Bode's Law, which can be used to derive the distances between the Sun and some of its planets.) Second, law may serve as a more forceful synonym for theory. (An example here is Newton's law of gravity -- which is, in fact, a theory.) The writers of Exploring Physical Science have hopelessly confused the situation: They define law according to the second meaning, but they describe a "law" in a way that reflects the first meaning!

As I leave chapter 1, let me note one of its glaring omissions: At no point do the writers even mention the iterative nature of scientific inquiry -- yet iteration is, in my opinion, the most important aspect of the scientific process. Construct a hypothesis; then test the hypothesis by gathering observations; then, if there are discrepancies between observations and predictions derived from the hypothesis, modify the hypothesis; repeat as needed. This repetitive process enables scientists to come progressively closer to an understanding of nature, though their understanding may never be perfect. There is no explanation of this process in chapter 1 of Exploring Physical Science or (as nearly as I can tell) in any other chapter.

• Page 64: "If you look at the windowpanes in a very old house, you will notice that they are thicker at the bottom than at the top. Over time, the glass has flowed slowly downward, just like a liquid." This is a common piece of misinformation. Glass doesn't flow at any appreciable rate, and the shape of a windowpane doesn't undergo any perceptible change, even over several human lifetimes. The real reason why an old pane may be thicker at its bottom than at its top is much simpler: The methods by which window glass was produced in, say, the 18th century were not as precise as the methods we use now, and the thickness of a pane might vary from place to place. If one edge of a pane was especially thick, installing the pane with its thick edge down was easier than installing the pane with its thick edge up.

• In text on page 121, the writers say that "The mass of a proton is 1 amu [atomic mass unit]," and then they declare: "Neutrons have slightly more mass than protons. But the mass of a neutron is still considered to be 1 amu." The writers thus contradict the table on page 126, which shows the mass of a proton to be 1.0073 amu and the mass of a neutron to be 1.0087 amu. This inconsistency is something new: In earlier versions of Exploring Physical Science, the inaccurate value (1 amu) appeared in both the text and the table. Now that Prentice Hall's writers have corrected the table, I wonder how long it will take them to fix the text.

• Page 123: "Any sample of an element as it occurs in nature contains a mixture of isotopes." That categorical statement is false. Beryllium, as an example, occurs in nature in only one form, not as a mixture of isotopes. The same is true of fluorine, sodium, aluminum, phosphorus, manganese, arsenic, gold, iodine, bismuth and various other elements.

• Page 123: The writers say that an element's atomic mass is "the average mass of all the naturally occurring isotopes of that element." Here we have an incorrect definition of an incorrect term. An atomic mass isn't an average of anything -- it is the mass of a single isotope. The "average" that the writers have in mind is the element's atomic weight, and the writers are wrong when they state that an element's atomic weight is simply the mean of the masses of all of the element's isotopes. In a calculation of atomic weight, the mass of each isotope is multiplied by a factor which reflects the isotope's relative abundance on Earth.

• On page 128, in a section called "Forces Within the Atom," we read: "The weak force is responsible for a process known as radioactive decay. During radioactive decay, a neutron in the nucleus changes into a proton and an electron." There are three errors here. First: Not all modes of radioactive decay depend on the weak force. Some modes are manifestations of the strong force. Second: When a neutron decays, it turns into a proton, an electron and an antineutrino. Third: There are additional modes of decay that involve the weak force -- modes other than the one that the writers have tried to describe.

• Page 128: "The role of gravity in the atom is not clearly understood." Gravity plays no appreciable role within the atom.

• Page 138: "Mendeleev designed a periodic table in which the elements were arranged in order of increasing atomic mass." Mendeleev dealt with atomic weights. He knew nothing of atomic masses, and he didn't know that a given element could occur as multiple isotopes.

• Page 180: "In nature, it is a general rule that opposites attract." This sentence is descended from one that appeared in the Prentice Hall middle-school book A Voyage of Discovery, published in 1986. A Voyage of Discovery contained the statement that "In nature, it is a general rule that opposite charges attract" -- a statement that was more or less accurate but was needlessly watered down. The writers of Exploring Physical Science have fixed that. They have changed "opposite charges" to "opposites," so now the statement is just plain wrong.

• Page 234: "Oil, which is a mixture of organic compounds, floats on water because the two liquids are insoluble." No, the oil floats because it is less dense than water. The oil remains distinct from the water because the two liquids are insoluble.

• Page 242: "Ethanol is used in medicines. It is also the alcohol used in alcoholic beverages. In order to make ethanol available for industrial and medicinal uses only, it must be made unfit for beverage purposes. So poisonous compounds such as methanol are added to ethanol. The resulting mixture is called denatured alcohol." What? Poisonous compounds are added to medicinal ethanol? No, of course not! As for industrial ethanol: It is true that ethanol is spiked with poisonous denaturants before it is sold for use in industrial processes, but Prentice Hall's writers seem not to know that this is done for political reasons, not technical reasons. The denaturing is mandated by laws that facilitate the federal government's regulation and taxation of alcoholic beverages.

• Page 269: "A beta particle is an electron. However, a beta particle should not be confused with an electron that surrounds the nucleus of an atom." The student will certainly infer that a beta particle and an electron are different things. The truth is that beta particles are identical with electrons in all ways.

• Page 272: "There are four types of nuclear reactions that can occur. . . . You will now learn about each type of nuclear reaction." In the passage that follows, the student reads about three nuclear reactions: alpha decay, beta decay and gamma decay.

• Page 272: "In each type [of nuclear reaction], the identity of the original element is changed as a result of the reaction." This isn't true for gamma decay -- and indeed, the caption under figure 11-7, on the next page, asks: "Which type of decay does not result in a different element?"

• On page 282: "The temperature conditions required for nuclear fusion exist on the sun and on other stars." No, the conditions required for nuclear fusion exist in the sun and in other stars. This distinction is important. Fusion reactions take place deep within a star, not on the star's surface.

• Page 288: In the section "Putting Radioactivity to Work," the writers mention radioactive tracers, radioimmunoassays, and "nuclear magnetic resonance imaging (MRI)." MRI technology does not involve radioactivity.

• Page 314: "The stopping distance of a car is directly related to its momentum." This statement, which was transfused into Exploring Physical Science from Prentice Hall's Motion, Forces, and Energy, is dead wrong: The stopping distance of a car is directly related to the car's kinetic energy, not to its momentum. The Prentice Hall editors certainly know that their statement is erroneous, because Lawrence S. Lerner explained the error, several years ago, in his review of the 1993 version of Motion, Forces, and Energy [note 5].

• Page 315: "Now suppose that you send two moving billiard balls into each other. . . . [T]he total momentum of the billiard balls before they hit and after they hit must be the same. Although their individual momentums may change, because of either a change in speed or mass, the total momentum does not change." In the situation described, a ball's velocity may change, but its mass doesn't.

• Page 328: "Automobiles are able to stop because the action of the brakes increases friction between the tires and the road." Oh, man! Here is another statement that is dead wrong and that was exposed in Lawrence S. Lerner's review of the 1993 Motion, Forces and Energy [note 5]. Why do Prentice Hall's editors continue to print and reprint material that they know to be erroneous?

• Pages 362 and 363: Figure 14-18 and the accompanying text purport to explain the generation of lift by an airplane wing. Prentice Hall's "explanation" is fictitious, and it denies a fundamental law of physics -- Newton's third law of motion. It is the same fictitious "explanation" that appears in another Pearson schoolbook, Scott Foresman - Addison Wesley Science Insights: Exploring Living Things [note 6].

• Page 363 carries "Attack of the Shower Curtain," an article that Prentice Hall has been printing and reprinting since 1993. The student is supposed to explain why a shower curtain moves when the shower is running. Then the teacher -- relying on a pedagogic note in the teacher's edition of Exploring Physical Science -- is supposed to disclose the correct explanation. The "explanation" given in the teacher's edition is entirely wrong [note 7].

• Page 365: Here we find a full-page article called "Up, Up, and Away," which allegedly deals with flight. The writers devote half of the page to repeating their fictitious claims about how an airplane wing works.

• Page 409: "Momentum must be conserved because energy is conserved." The conservation of energy is a far more important concept than is the conservation of momentum -- moreover, momentum is conserved only in the absence of external forces. Prentice Hall's slogan "Momentum must be conserved because energy is conserved" exemplifies the deep conceptual confusion that runs throughout chapter 15 ("Work, Power, and Simple Machines") and chapter 16 ("Energy: Forms and Changes"). In these chapters, the relationships among energy, momentum, force, power and work are hopelessly muddled.

• Page 482: "The terms positive and negative, which have no real physical significance, were originally decided upon by Benjamin Franklin when he first discovered charge." Ben Franklin did not discover charge.

• Page 498: "At very low temperatures, however, the resistance of certain metals becomes essentially zero. Materials in this state are said to be superconductors. In superconductors, almost no energy is wasted." Maybe the Prentice Hall writers really don't grasp the marvels of superconductivity, or maybe they are adhering to their usual practice of weakening their statements until the statements become false. The resistance in a superconductor is zero (not "essentially zero"), and no energy is wasted. The claim that "almost no energy is wasted" is wrong and misleading.

• Page 504: In a section on "Circuit Safety Features," the writers cite two reasons why an electrical circuit in a house may create "the danger of fire": The circuit may be overloaded and may draw so much current that the wires become too hot, or the wires may be old and frayed. So far, so good. But then the writers say that protection against this danger of fire is provided by fuses and circuit breakers. The writers' statements aren't all wrong, but they lead to the ridiculous conclusion that fuses and circuit breakers can somehow nullify the fire hazards presented by old and frayed wires! If the writers really believe this, their ignorance of the subject matter must be profound.

• Page 527: "Many scientists believe that short-term changes in the Earth's weather are influenced by solar particles and their interaction with the Earth's magnetic field." That statement may be accurate if one uses a generous definition of the word scientists -- generous enough to include the "scientists" who show up on television programs and tell us that they believe in alien abductions, astrology, chiropractic, extrasensory perception by household pets, and other examples of nonsense. In any case, vague claims about beliefs are completely unacceptable in a science book, as I pointed out when I reviewed Prentice Hall's middle-school book Exploring the Universe [note 8]. In a scientific context, what people "believe" is not an issue. The things that matter are observations and reason and predictions from scientific theories. When the writers of a science book couch a topic in terms of mere belief, they project a false perception of science.

• Page 535: "Engineers . . . are now involved in the development of trains that 'float' above the track. The trains are called maglev trains, which stands for magnetic levitation. Because a maglev train has no wheels, it appears to levitate." What a ridiculous statement! A maglev train "appears" to levitate because it does levitate: It floats in the air, supported by a mechanism which is invisible. (To top things off, many maglev trains have wheels.)

• Page 574: "The most advanced memory chip can store as much information as 1 million vacuum tubes can." That statement was correct in 1985 or so, but now it is laughable.

• Page 576: "Software must be precise because in most cases a computer cannot think on its own." This is unforgivable. In no case can any computer that exists today think on its own.

• Page 576: "Computer circuits are composed of diodes. As you learned in the previous sections, diodes are gates that are either open or closed to electric current." In almost all computer circuits the basic elements are transistors, not diodes. Moreover, the claim that "diodes are gates" reinforces the confusion that the writers created on page 560, where they gave this account of the vacuum diode: "Because the electrons moved in only one direction, this vacuum tube acted as a one-way valve, or gate, for a flow of electrons." The comparison to a check valve ("one-way valve") was valid, but the reference to a gate was misconceived. The gates that students encounter in real life aren't one-way devices.

• Page 617: Here we read that Amerindians (presumably on the Great Plains) put their ears to the ground so that they could detect herds of prey animals: "By listening for sounds in the ground, they could hear the herds much sooner than if they listened for sounds in the air. The speed of sound in the ground at 20º C is 1490 m/sec -- more that four times as fast as in air." Here the writers must be kidding. Could any adult actually believe that claim about hearing the herds "much sooner"? Indians (and cowboys, too) pressed their ears to the ground because sound travels farther in soil than in air, so herds could be detected at greater distances. (The fact that sound also travels faster in soil wasn't significant. If a herd were 5 kilometers away, an Indian with his ear to the ground would have detected the herd only 11 seconds sooner than an Indian who was listening for sounds propagated through the air.)

• Page 623: "Have you ever found yourself tapping your foot to the beat of a good tune? Perhaps you have even said that you liked one song better than another because it had a faster or a slower beat. Beats result from the interactions between waves." It's a pun! -- or is it? The beats resulting from interactions among waves are completely unrelated to the "beat" of a piece of music.

• Page 648: "The sound portions of most television broadcasts are carried as AM waves while the picture portions are carried as FM waves." False. Both the audio signals and the video signals are broadcast as FM waves.

• Page 660: ". . . science is a way of explaining observations; it is not absolute knowledge." What does this mean? What is absolute knowledge?

• Page 675: "The index of refraction is the comparison of the speed of light in air with the speed of light in a certain material." No. An index of refraction isn't just any form of "comparison" that one might choose to make. An index of refraction is, quite specifically, a ratio -- and it doesn't involve air. A material's index of refraction is the ratio of the speed of light in a vacuum to the speed of light in the material.

• Page 694: "A laser consists of a tube containing gases, liquids, or solids. The element used is chosen by the properties of the laser light it produces." The lasing material in a laser is seldom a single element. It is typically a mixture of substances, which may include compounds as well as elements.

• Page 694: "The most common type of laser is the helium-neon laser." This may have been true in the late 1980s. Today the most common lasers are semiconductor lasers, which are used in CD-players, laser pointers, and other consumer products.

• Page 696: When describing the reflection that occurs as light is transmitted through optical fibers, the writers say: "This type of reflection is known as total internal reflection. Very little light is lost when it is totally reflected." Wrong. Total internal reflection is exactly that -- total. This means that no light is lost from the transmitting medium. Here again the writers have equivocated and have watered a statement down until the statement has become false.

• Page 698: Here the writers claim that the human visual system can create the perception of depth because "At certain points, the reflected light waves [from an object] overlap and interfere with one another. The interference pattern of the reflected waves gives the object its depth." Then the writers attempt to explain holography: "Instead of recording an image, holography uses a laser beam to record the entire interference pattern created by the light reflected from an object -- just as your eyes do." This is totally nonsensical. Our capacity to perceive depth depends on our binocular vision and on assumptions that we make about the characteristics of objects. The techniques used for producing and viewing a hologram are not at all analogous to the workings of the human visual system.

It is important to recognize that the book would be unacceptable even if all of its factual errors were corrected. Even without those errors, Exploring Physical Science still wouldn't meet the tests of a science textbook. A science textbook should offer good writing, with sentences grouped rationally into paragraphs, and with paragraphs grouped into larger units built around themes. A science textbook should explain concepts, not just state them, and it should provide explanations that can be understood by students. A science textbook should relate concepts to each other and to the real world. Exploring Physical Science fails on each and every count.

Notes

1. Editor's note: See "Educators Should Avoid This Book Like the Plague" in TTL, September-October 1995. [return to text]

2. Editor's note: See "First the Hoopla -- Then the Whitewash," the article that begins on page 7 of this issue. [return to text]

3. Editor's note: The Prentice Hall Science series comprises nineteen schoolbooks. The original versions of all nineteen were dated in 1993. Seven of the Prentice Hall Science books have been reviewed in TTL, and all of the reviews are now available on The Textbook League's Web site at http://www.textbookleague.org/51prensci.htm [return to text]

4. Editor's note: See "It Isn't Even Wrong" in TTL, July-August 1999. [return to text]

5. Editor's note: Lawrence S. Lerner's review of Motion, Forces, and Energy appeared in TTL, November-December 1992. [return to text]

6. See "On Wings of Ignorance" in The Textbook Letter for November-December 1999. [return to text]

7. See "Fun in the Tub" in The Textbook Letter, July-August 1998. [return to text]

8. Editor's note: Leonard Tramiel's review of Exploring the Universe appeared in TTL, January-February 1999. [return to text]

Leonard Tramiel, of Palo Alto, California, is a computer programmer and an amateur astronomer. He holds a doctorate in astrophysics from Columbia University. He teaches astronomy in local schools, as a volunteer, under the auspices of Project Astro, sponsored by the Astronomical Society of the Pacific.

Addendum

For more information about erroneous material in the 1999 version of Exploring Physical Science, see the article "Sink, Sank, Sunk" in TTL for January-February 2000.

return to top go to Home Page read our Index List, which shows all the textbooks, curriculum manuals,      videos and other items that are considered on this Web site subscribe to The Textbook Letter order back issues of The Textbook Letter support the work of The Textbook League The Textbook Letter is published, copyrighted and distributed by The Textbook League (P.O. Box 51, Sausalito, California 94966)