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About this Evaluation Report Content Analysis 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. |
In level B, Chapter 9: Wear and Tear, and level C, Chapter 3: Gulp! the student text uses consistently the term “particles,” but there is no discussion of atoms and molecules. In level 1, Chapter 2: Construction Materials, the material begins to use the terms “atom” and “molecules” alongside the term “particles.” However, the material never explicitly points out that the “atoms” and “molecules” are the particles that were discussed in the previous levels. The material explicitly points out that all substances are made up of particles in only one instance. In addition, it does not attempt to contrast the particle theory to naive theories (matter is continuous or matter just includes particles) as the statement of the key idea does.
Idea
b: These particles are extremely small—far too small
to see directly through a microscope.
The idea that “[a]ll matter is made up of tiny particles”
is listed as a key point in the material (level C, Chapter
3: Gulp!, p. 146t). In the student text, “tiny particles”
is briefly mentioned four times (over three years, levels
B, C, and 1) (for example, “Everything consists of
tiny particles” [level C, pp. 62–63s]). In addition,
the Teacher’s Guide (but not the student text) relates
three activities to the small size of particles: The fact
that chlorine can be smelled above a swimming pool is used
to suggest that “some of the chlorine is escaping
from the water. Anticipating later lessons in this chapter,
this can be discussed in terms of particles of chlorine
(too small to see) being spread through the water and escaping
into the air” (level C, p. 124t). In the activity
that follows, students evaporate tap water and discover
a solid residue, which is explained in the Teacher’s
Guide as “the solid residue must have come from the
water, which had tiny particles of the dissolved substance
spread out through it” (level C, p. 130t). In a subsequent
activity, students look at tea bags under a microscope and
at the process of making tea (as a drink). They see the
color of tea spreading out in the water, and (after seeing
that the holes in tea bags are too small to let actual bits
of tea leaves out) are led to conclude that the tea can
get out only if it is made of very small particles. However,
the idea that “particles are too small to see directly
through a microscope” is not explicitly stated in
the student or teacher materials.
Idea
c: Atoms and molecules are perpetually in motion.
Idea
d: Increased temperature means greater molecular motion,
so most substances expand when heated.
The connection between temperature and molecular motion
is listed as a “key point” for lesson 8 in Chapter
3: Gulp! (level C, p. 146t). The connection between increased
motion of particles and thermal expansion is implied in
a key point listed in level 1, Chapter 11: The Atmosphere:
“Increasing temperature of air causes the density
of air to decrease as a result of the molecules being spread
farther apart” (p. 730t, vol. II). However, this statement
mentions only air, and does not mention solids or liquids
or even other gases. In level C, Chapter 3: Gulp! students
observe that tea spreads out faster into a cup of hot water
than into a cup of cold water, and that the rate at which
gas is given off when soda is heated is greater at higher
temperatures. The Teacher’s Guide links these activities
to the idea that increased temperature means greater molecular
motion (part of Idea d) (e.g., “Discussion now develops
the idea that the particles of water are constantly moving,
and that they move faster at higher temperatures…”
[p. 137t]), but this link is not presented in the student
book. The student text notes the connection between temperature
and increased molecular motion in only one instance in the
middle school materials in the context of explaining evaporation:
“When a substance is heated, energy is transferred
to the particles. This energy causes the particles to move
more vigorously” (p. 63s). Twice in level 1 the student
text presents the idea that when a substance is heated,
its molecules move faster, once in the context of explaining
why warm air rises and then in the context of explaining
the three gas laws. In the same chapter, the material also
makes the connection between increased molecular motion
and thermal expansion of gases two times: once in the student
book in the context of the gas law linking volume and temperature,
and again in the Teacher’s Guide in the context of
an activity in which students compare the circumference
of a balloon when it is placed in a hot bath and a cold
bath. The material does not explain the thermal expansion
of solids and liquids at a molecular level.
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.
The different arrangement of particles in solids, liquids,
and gases and the different motion of particles in liquids
and gases are listed as key points in lesson 8 of Chapter
3: Gulp! (level C, p. 146t). The idea that there are forces
between particles in solids, liquids, and gases and that
the strength of these forces is different in the three states
is not explicitly listed as a key point. However, some aspects
of this key idea are implied in the key point, “Structure
and composition affect the properties of a material”
(level 1, Chapter 2: Construction Materials, p. 95t). In
level C, Chapter 3: Gulp! students compare the density,
squashability, and “move-through-ability” of
solids, liquids, and gases. The different arrangement of
particles in solids, liquids, and gases and the different
motion of particles in liquids and gases are presented in
the student text, and the Teacher’s Guide links these
to the different properties of solids, liquids, and gases.
In level 1, Chapter 2: Construction Materials, the student
text represents the arrangement of particles in solids,
compares the arrangement and motion of particles in solid
and liquid salt and glass, and links the density of metals
to the arrangement of their atoms. It also links properties
of wood, fired clay, and plastics to the forces between
their molecules.
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.
The molecular explanation of changes of state is not listed
as a key point in PRIME Science. In level C, Chapter 3:
Gulp! brief explanations of melting and evaporation are
presented in the student material, but they do not account
for changes of state step-by-step in terms of changes in
the arrangement, interaction, and motion of particles: “In
a solid the particles begin to vibrate more vigorously until
the regular pattern of the solid is broken down and the
particles become free to move around. In a liquid the particles
eventually gain sufficient energy to escape from the liquid”
(p. 63s). Explanations of melting and evaporation are followed
by questions that ask for explanations of solidifying and
condensation, but there are no clear instructions that students
should respond to these questions. The Teacher’s Guide
includes similar brief explanations for freezing and condensation
(for example, “Cooling gases removes energy until
the particles can no longer keep apart and the gas condenses”
[p. 148t]). It is not clear whether teachers are expected
to relate these explanations to their students. In level 1, Chapter 2: Construction Materials, the student
materials include brief descriptions of cooling of liquid
sodium chloride and liquid glass at the particle level.
The descriptions focus more on the final state (solid substance)
rather than account for the cooling process in terms of
changes in the arrangement, interaction, and motion of particles
(p. 33s).
PRIME Science does not provide tasks, questions, or text that clearly tie together the distributed experiences students have with the key ideas, nor does it prompt teachers to make such connections. For example, when students are introduced to particles in level C (chapter 3), they are not reminded of their previous experiences with the idea of particles in level B (chapter 9). Likewise, when the “kinetic theory of gases” is introduced in level 1 (chapter 11) to explain the pressure of gases and the gas laws, it is not connected to the particle theory of matter that was described in level C (p. 320s).
At a finer grain size, the experiences that students have with the concepts of particles, atoms, and molecules are not linked with each other. In the chapters that relate to the key ideas in levels B and C, the student text consistently uses the term “particles,” and there is no discussion of atoms and molecules. In level 1, Chapter 2: Construction Materials, the material begins to use the terms “atom” and “molecules” alongside the term “particles.” However, the material never explicitly points out that the “atoms” and “molecules” are the “particles” that were discussed in the previous levels. (It should be noted that the term “atom” appears to be introduced for the first time in level C, Chapter 8: Metals, but it is not defined. Without any preparation, in the context of interpreting formulas, students are asked how many oxygen atoms are paired with each atom of magnesium in magnesium oxide [p. 193s]. The index in level C includes the term “particles” but not the term “atoms.”) The lack of questions, readings, or other activities that would help students make connections between the different instances in which the key ideas are addressed is an important issue is this material, given that the material organizes chapters around themes (such as “drinks” in chapter 3: Gulp!) rather than a set of coherent ideas.
The material makes a few connections between the key ideas and other ideas in level 1, but students are never engaged in making or explaining the connections. For example, after designing an experiment to test how hydrogen-chloride concentration is related to reaction rate, the connection between concentration and reaction rate is related to the random motion of liquid HCl particles (level 1, chapter 2, p. 48s). The connection is adequately explained, but there is no mention in the Teacher’s Guide of how this page would be used or discussed.
There are also many missed opportunities for connections. Early in level C, Chapter 3: Gulp! students are introduced to the “water cycle” (pp. 48–49s). The text states that “[b]y the time you have finished this chapter you should be able to explain the water cycle in detail” (p. 48s). However, in the In Brief section at the end of the chapter, the only connection between the particle model and the water cycle consists of two statements: “During evaporation, energy is transferred to the water particles,” and “During condensation, energy is transferred from the water particles” (p. 64s). In level 1, Chapter 11: The Atmosphere, students review the question, “Where does rain come from?” by observing and discussing water condensing on the outside of a cold can (p. 324s; p. 749t, vol. II). However, no connection is made between the particle theory and the “water cycle.”
However, the chapters in which the kinetic molecular theory
is addressed sometimes go beyond the science literacy recommendations
in their treatment of other topics. Even so, it should be
noted, that the text goes beyond the recommendations by including
content that is more detailed and technical, rather than content
that is developmentally too advanced for the intended audience.
For example, in level C, Chapter 3: Gulp! in the context of
water supplies and, in particular, in discussing sanitation
and water purity, the unit introduces details of the sewage
treatment process, of using chlorine to kill bacteria in drinking
water, and of how the pH of drinking water needs to be adjusted
after using chlorine. It also discusses minerals in water
and water hardness.
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 soley in illustrations. Specifically, 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.).
