AAAS Project 2061 Textbook Evaluations

## Middle Grades Science Textbooks: A Benchmarks-Based Evaluation

Glencoe Earth Science, Life Science, and Physical Science. Glencoe/McGraw-Hill, 1997
 Earth Science Life Science Physical Science

 1 About this Evaluation Report 2 Content Analysis 3 Instructional Analysis
 [Explanation] This section examines whether the curriculum material's content aligns with the specific key ideas that have been selected for use in the analysis. [Explanation] This section examines whether the curriculum material develops an evidence-based argument in support of the key ideas, including whether the case presented is valid, comprehensible, and convincing. [Explanation] This section examines whether the curriculum material makes connections (1) among the key ideas, (2) between the key ideas and their prerequisites, and (3) between the key ideas and other, related ideas. [Explanation] This section notes whether the curriculum material presents any information that is more advanced than the set of key ideas, looking particularly at whether the “beyond literacy” information interrupts the presentation of the grade-appropriate information. [Explanation] This section notes whether the curriculum material presents any information that contains errors, misleading statements, or statements that may reinforce commonly held student misconceptions. References

Alignment

Idea a: All matter is made up of particles called atoms and molecules (as opposed to being continuous or just including particles).
There is a content match. The idea that all matter is made up of particles is presented in several locations in the student text. It first appears in Chapter 5: Energy, Section 5.2: Temperature and Heat, in the subsection Matter in Motion (p. 134s). Thereafter, the idea of particles is used to define temperature and thermal energy and to explain the conduction of heat. The idea that “tiny particles in constant motion make up all matter” is identified as the kinetic theory of matter in Chapter 8: Solids, Liquids, and Gases, Section 8.1: Matter and Temperature, in the subsection Solids (p. 215s). Then the properties of the three common states of matter and thermal expansion are explained in terms of the differences in the arrangement and movement of their particles.

In chapters 5 and 8, the student text generally refers to “particles,” rather than to atoms or molecules. In Chapter 9: Classification of Matter, before the material addresses elements and compounds, it states that “[t]he units that make up all matter are called atoms” (p. 246s) but it does not link the idea of particles, as discussed in preceding chapters, to atoms. The material uses the phrase “all matter” consistently; however, it does not attempt to contrast the atomic theory to naive theories (such as matter being continuous or including particles only), as the statement of the key idea does.

Most mentions of this key idea are brief and are given in the body of the student text—as, for example, “Tiny particles in constant motion make up all matter” (p. 215s). However, some of them consist only of drawings of balls that represent atoms; for example, green (chlorine) and gray (sodium) balls represent atoms in a salt crystal (p. 215s). Although mentioned often, the idea is not developed.

In Chapter 10: Atomic Structure and the Periodic Table, the student text states, “The idea of atoms began more than 2400 years ago with Greek thinkers, who defined atoms as the smallest parts of matter” (p. 270s). However, it immediately contradicts this statement without comment by declaring, “Atoms consist of a positively charged center, or nucleus, surrounded by negatively charged particles called electrons” (p. 270s).

Idea b: These particles are extremely small—far too small to see directly through a microscope.

There is a content match. The idea is stated almost verbatim a few times (for example, “All matter is made up of particles so small that you can’t see them, even with an ordinary microscope” [p. 134s]), but it is not developed.

Idea c: Atoms and molecules are perpetually in motion.

There is a content match. The idea that particles are moving constantly is presented in several places in the student text, and a possible student difficulty is addressed: “The particles that make up any object are constantly moving, even if the object itself appears perfectly still” (p. 134s). Additional comments mention the motion of particles of solids, liquids, and gases without noting the perpetual nature of the motion. Examples include gases spreading out to fill their “containers” (p. 217s), pressure (p. 228s), and the properties of solids, liquids, and gases (pp. 214–217s).

Idea d: Increased temperature means greater molecular motion, so most substances expand when heated.

There is a content match. The idea that increasing the temperature of a substance (or “heating it,” used interchangeably in this material) increases the motion of the substance’s particles is introduced in Chapter 5: Energy. It is used often in Chapter 8: Solids, Liquids, and Gases. In chapter 5, it is introduced after the definition of temperature: “As the particles in an object move faster. . .the temperature of the object rises” (p. 135s). Then the key idea is used to explain the concept of thermal energy and, in Chapter 6: Using Thermal Energy, the transfer of heat energy by conduction and convection. Chapter 8 uses the idea of increased molecular motion to explain the thermal expansion of solids and liquids and the relationship between the temperature and the volume of a gas. Several statements link greater particle motion to thermal expansion in contexts relating to solids (for example, a stuck jar lid; expansion joints [p. 219s]); liquids (as in thermometers [p. 220s]); and gases (as in air in a closed soda bottle put in a freezer [p. 231s]; air in a closed plastic bag warmed with a hair dryer [p. 230t]). No activities are presented that link the key idea (increased temperature means greater molecular motion) with increased dissolving or diffusion rates.

While the material takes the overall approach of teaching about energy before it teaches about matter, it does not connect regularly increased temperature to greater average energy of motion. Only a few statements make this connection explicitly, such as the definition of temperature in chapter 5 (“Temperature is a measure of the average kinetic energy of the particles in a sample of matter” [pp. 134–135s]). In explanations of thermal expansion and changes of state, the text mostly uses the idea that increased temperature means increased particle motion.

Idea e: There are differences in the arrangement and motion of atoms and molecules in solids, liquids, and gases. In solids, particles (1) are packed closely, (2) are (often) arranged regularly, (3) vibrate in all directions, (4) attract and “stick to” one another. In liquids, particles (1) are packed closely, (2) are not arranged regularly, (3) can slide past one another, (4) attract and are connected loosely to one another. In gases, particles (1) are far apart, (2) are arranged randomly, (3) spread evenly through the spaces they occupy, (4) move in all directions, (5) are free of one another, except during collisions.

There is a content match. All parts of this key idea are presented, with the exception of the one stating that solids “vibrate in all directions.” Most examples occur in the context of describing the characteristics of states of matter and comparisons among them. In particular, statements link the arrangement and motion of—and the forces between—particles to the properties of solids, liquids, and gases. One such statement is as follows:
The particles in solid matter are held close together by forces between them. This is why a solid can’t be squeezed into a smaller space. The particles can vibrate close to their neighbors, but they lack enough energy to move out of position. Thus, they lack enough energy to move over or around each other. This explains why a solid holds its shape. [p. 215s]

Idea f: Changes of state—melting, freezing, evaporating, condensing—can be explained in terms of changes in the arrangement, interaction, and motion of atoms and molecules.

There is a partial content match. The following presentation of Idea f shows which parts of the idea are treated (in bold) and what alternative vocabulary, if any, is used (in brackets): Changes of state—melting, freezing, evaporating, condensing—can be explained in terms of changes in the arrangement, interaction, and motion of atoms and molecules.

It is an explicit objective of the student text that students will be able to “interpret state changes in terms of the kinetic theory of matter” (p. 224s). However, most of the observations that relate to changes of state emphasize the flow of energy into or away from a material in the process of changing state, or they emphasize that during melting and evaporation, forces between particles are overcome. For example, the text includes this molecular explanation of the evaporation of water from freshly poured concrete: “Freshly poured concrete includes liquid water spread into a thin layer over a large surface area. As the water particles gain energy, they can overcome attractions to other particles and evaporate, leaving behind a dry, solid surface” (p. 224s).

The student text does not present any explanations of freezing and condensation at the molecular level. In a Reteach section (p. 226t), though, students are asked to make sketches of particles representing their changes of state (presumably including freezing and condensing). The kinds of sketches that students are expected to draw in this activity are not indicated.

Building a Case

The student text typically asserts the key ideas without developing an evidence-based argument to support them. In teaching the kinetic molecular theory, the material explains various phenomena in terms of the theory. For example, in addressing the nature of liquids, Chapter 8: Solids, Liquids, and Gases presents a paragraph that describes their observable characteristics and then says that the kinetic theory also “explains the properties of liquids. Because a liquid can’t be squeezed, its particles must also be close together…. However, they have enough kinetic energy to move over and around each other” (p. 216s). Later, chapter 8 applies the theory to explain thermal expansion:
You have learned how the kinetic theory accounts for characteristics of different states of matter you see and touch every day. The kinetic theory also explains other things you may have observed. For example, have you ever noticed the strips of metal that run across the floors…? [p. 219s]

One way to convince students about the truth of a theory is by showing its explanatory power. Although this material provides several phenomena that the kinetic molecular theory helps to explain, it does not establish explicitly the fruitfulness of the theory.

Coherence

Information related to the key physical science ideas is distributed primarily in Chapter 5: Energy and Chapter 8: Solids, Liquids, and Gases. The text does not alert teachers to the distribution of the experiences it provides for these ideas, does not convey the logic for the sequence of the experiences, and rarely connects the experiences provided to each other. For example, the first mention of the kinetic theory is buried in the discussion of temperature given in Chapter 5, Section 5.2: Temperature and Heat (p. 134s) in a way that allows for no preparation or justification of the theory’s concepts and components (p. 134s). When the kinetic theory is presented again in chapter 8 in the context of explaining the characteristics of solids (pp. 214–215s), no reference is made to the presentation in chapter 5. However, in chapter 8, experiences with the kinetic molecular theory appear to be sequenced logically and to be better connected.

The student text links the kinetic molecular theory to some related ideas. For example, it links the motion of particles to the idea of heat transfer by particle collisions (p. 152s) and to the faster transmission of sound waves at higher temperatures (p. 507s). While the first connection is explained adequately in the text, the second is not.

The introductory pages of the Teacher Wraparound Edition link four themes (energy, systems and interactions, scale and structure, and stability and change) to each chapter in the program (pp. 10–11T). For example, chapter 8 is linked to the theme of energy (p. 11T). Each chapter includes a section entitled Theme Connection that is intended to explain how the topic in the student text relates to a given theme. These sections are rather vague and do not identify the specific ideas (from the theme and the chapter) that are connected; so they are unlikely to help teachers enable their students to make sense of important connections in science. The Theme Connection (Energy) for chapter 8 is an example: “The energy content, or temperature, of particles plays a major role in determining their state of matter. The kinetic theory of matter presents a way for students to visualize particles in motion and to form a mental model of the states of matter” (p. 212t).

Beyond Literacy

The text goes far beyond the key idea that all matter is made up of particles called atoms and molecules (Idea a). When treating the kinetic molecular theory, the text includes some content beyond the scope of the key ideas, such as crystalline and noncrystalline solids, the heat of vaporization and the heat of fusion, and the pascal as the unit of pressure. The last section of Chapter 8: Solids, Liquids, and Gases includes discussions of Archimedes’, Pascal’s, and Bernoulli’s principles. These principles also go well beyond the scope of science literacy for middle grades students.

Accuracy

The evaluation teams developed a summary assessment of the most common kinds of errors found in each of the three subject areas—physical science, Earth science, and life science. In this context, “errors” is taken to mean not only outright inaccuracies, but also those instances in which the material is very likely to lead to or support student misconceptions. Overall, inducement to misconstrue is the most serious problem of accuracy in the evaluated materials.

The evaluation teams’ collective findings, presented below, should be taken as having general applicability to all of the evaluated materials, not complete and specific applicability in toto to any one of them.

Identified errors occur most frequently in drawings and other diagrams. They take the form of representations that are likely to either give rise to or reinforce misconceptions commonly held by students. Following are physical science examples of the kinds of misleading illustrative materials of most concern to the evaluation teams:

• Diagrams and drawings that show atoms or molecules of solids, liquids, and gases in colored backgrounds (for example, water molecules inside blue drop shapes) and that thereby can initiate or reinforce the misconception that particles are contained in solids, liquids, and gases, in contrast to the correct idea that substances consist of particles (with empty space between particles). This misconception may be further reinforced by the wording of diagram labels, such as “solid particles in solid water and water particles in liquid water” (emphasis added). Similarly, statements such as “explanations for what is inside things” may imply that matter contains particles (as well as other things), rather than that matter is made of particles.

• Diagrams of solids (and occasionally liquids) that do not depict the motion of atoms or molecules can give rise to, or reinforce, the misconception that atoms or molecules of solids (or liquids) are still.

• Diagrams that show molecules of liquids much farther apart than the molecules of solids are misleading; in most liquids, molecules are only a little farther apart.

• Diagrams that show particles of a substance in the solid, liquid, and gaseous state in different colors can reinforce the erroneous idea that the particles themselves are different, not their arrangement and motion. Similarly, diagrams that show particles of a substance changing size as the substance changes state can give rise to the misconception that the molecules themselves change size, becoming larger when heated.

The use of imprecise of inaccurate language is problematic in text materials, not solely in illustrations. In physical science, language that does not maintain a clear distinction between substances and atoms or molecules can mislead students to attribute macroscopic properties or behavior (such as hardness, color or physical state) to individual atoms or molecules. For example, statements such as “the particles of perfume are moving farther apart as they change into a gas and diffuse throughout the air,” “write a story from the point of view of a particle in the solid phase as it melts and then evaporates,” and “draw what happens when the particles change state” (emphasis added) imply inaccurately that the particles themselves change state (melt, evaporate, etc.).