| Earth Science | Life Science | Physical Science |
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. |
Using this idea, students are asked to explain the evaporation of water from a solution that contains food coloring, the change of a balloon's circumference with a change in temperature, and the diffusion of food coloring in hot and cold water (pp. 201-205s). Then, the ideas that particles are in motion and that there are forces between the particles, are introduced, and students are asked to use the particle model to explain these phenomena again (pp. 206-208s). In the rest of chapter 10 and in Chapter 11: Using Models to Test and Predict, students are encouraged to use the particle model to help explain a variety of observations. In only some cases, either the Teacher's Edition or the student textbook refers explicitly to the idea that matter is made up of particles in the explanations given for these observations. For example, when students are asked to explain the diffusion of food coloring in hot and cold water, it is suggested that the teacher provide hints if the students are stuck: "Basically, according to the theory, food coloring is made of particles and so is water. When you put food coloring in water, the particles tend to mix" (emphasis added) (p. 207t). Or, in chapter 11, students use a medicine dropper to place drops of water on the surface of a penny. They count the drops until the first drop of water spills over the edge of the penny. After critiquing an alternative model for the phenomenon, students read the scientifically correct explanation that uses the idea that "[w]ater is composed of tiny particles that have forces that constantly attract each other" (p. 238s).
No attempt is made to contrast the atomic theory with naive theories (for example, that matter is continuous or that matter includes particles), as the key idea does.
Idea
b: These particles are extremely small—far too small
to see directly through a microscope. Occasionally,
the material refers to particles as small or tiny, but there are no activities
or text that will help students appreciate that particles are extremely
small. In one instance, the text notes: However, this
statement is not made to stress the smallness of the particles, but rather
as proof that indeed matter is made up of particles. However, unless students
are familiar with the distinction between electron microscopes and light microscopes,
they might miss the point. It would have been more helpful to explain that
although the larger particles can be seen under an electron microscope, none
of the particles are visible under a light microscope.
Yes it is possible to observe large particles with an electron
microscope, which provides evidence that materials are made
of particles. We cannot see smaller particles,
though, which makes it difficult to gather evidence
about them. (p. 196s)
Idea
c: Atoms and molecules are perpetually in motion. Although this
key idea is a stated goal of Diversity and Limits, which stipulates
that "students should understand that the particles in all materials are in
constant motion" (p. 206t), the student text mentions only twice the idea
that particles are in motion, and it does not state anywhere that the particles
are perpetually in motion. In addition, although there are some activities
that relate to the idea that particles move faster at higher temperatures
and slower at lower temperatures, there are no activities that focus directly
on the concept that atoms and molecules are perpetually in motion.
Idea
d: Increased temperature means greater molecular motion,
so most substances expand when heated. The teacher's notes explain that students
should be able to use this key idea-that "increasing the temperature makes
particles move faster"-to demonstrate their understanding of the learning
goal that "particles in all materials are in constant motion" (p. 206t). The
connection to the expansion of materials is not presented as a specific goal.
Accordingly, there is a content match to the relationship between increased
temperature and increased particle motion, but the connection to the expansion
of materials is not made clear. The student text notes the connection between
temperature and particle motion and compares the motion of particles in hot
and cold water, hot and cold air, and warm and cold sheets of steel (pp. 206-207s).
Students are asked to explain a variety of phenomena that can be accounted
for with this idea, such as the different rates of diffusion of food coloring
in hot and cold water, and the increased or decreased circumference
of a balloon when it is placed beside a heat source or crushed ice (pp. 203-205).
Although the student text does not contain the explanations of these phenomena,
the notes in the Teacher's Edition suggest that students are expected
to use the idea that particles move faster at higher temperatures in their
explanations (p. 206t). In the balloon-related activity, students are expected
to connect the idea that increased temperature means increased particle motion
to the expansion of the air in the balloon (p. 207b).
However, the text does not connect this idea to the expansion of any other
substances (solids, liquids, or gases). With respect
to the connection between increased temperature and increased (particle) energy
of motion, the explanations of several phenomena included in the background
information (in the Teacher's Edition) relate the increased temperature
to the increased kinetic energy of the substance's particles, as, for example,
"Upon heating, most of the molecules found in air acquire more kinetic energy
and begin to move more rapidly" (p. 191bt). However, as elaborated in the
student text, the theory only talks about particles of hot water (hot air
and cold steel) moving faster than particles of cold water (cold air and cold
steel): "When particles move faster, the material gets hotter. When
particles move slower, the material gets colder" (pp. 206-207s).
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 teacher's notes present as explicit goals that students
understand "that there is a force of attraction between all particles of matter"
(p. 208t), and "that extending the particle theory to include the arrangement
of and interaction among particles helps improve our explanations for the
behavior of matter" (p. 216t). The force of attraction between particles of
matter is addressed, but not the arrangement of particles. In particular,
there is a content match to the idea that there are forces among particles,
and no match to the different arrangement and motion of particles in solids,
liquids, and gases. The idea that
there are forces among particles is mentioned several times in the student
textbook (e.g., pp. 206s, 216s, 218s). However, the focus is on the forces
of attraction among particles in liquids. Students are asked to explain surface
tension phenomena that demonstrate the cohesive forces holding water particles
together (pp. 236-240s). In addition, when students are asked to explain phenomena
in which water evaporates, the Teacher's Edition ties explanations
of these phenomena to the idea that forces among water particles are overcome
when the particles move faster. There are no activities that demonstrate the
forces between particles in solids or that illustrate the different strengths
of attraction among particles in solids, liquids, and gases. However, the
student text does mention once that "forces are stronger in solids than they
are in liquids. In a gas, the forces are even weaker" (p.
206s). The student text mentions
that "[o]ne way.to improve the
particle model is to specify how the particles are arranged
and how they interact with one another" (p. 216s), and that
"[n]ow you know several parts
of the particle model: particles in different materials
are uniquely arranged and have unique interactions" (p.
218s). However, there are neither text nor activities to support this statement.
The only place where the different arrangement of particles
is addressed specifically is in Patterns of Change
(level A), where, in the context of discussing the
water cycle, the text mentions in passing that particles
are farther apart in a gas and closer together in a liquid
(level A, p. 253s).
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.
In Patterns of Change (level A), the student
text describes evaporation and condensation in terms of
water particles moving into, and out of, respectively, the
air and the atmosphere, but not in terms of changes in the
arrangement, interaction, and motion of particles (level
A, pp. 238-253s.) In Diversity and Limits (level B),
students observe the evaporation of water from a water-food-coloring solution
(p. 202s). Students are asked to explain the phenomenon using the particle
model. The Teacher's Edition ties the evaporation of water to the idea
that increased temperature means increased particle motion and to the idea
of forces between particles of liquids (p. 207at). Later, students are asked
to explain a phenomenon that involves both the evaporation and condensation
of water using the particle model. However, they may or may not explain the
phenomenon in terms of the arrangement, interaction, and motion of particles.
The teacher's notes merely state: "You can expect the students to at least
try to include something about particles moving faster at higher temperatures
and slower at lower temperatures" (p. 210t).
In
Diversity and Limits (level B), Unit 2: Why Are Things Different? has
two goals. It explores the development and use of scientific
models and introduces the particle theory of matter. Specifically,
this unit attempts to illustrate the kinds of processes
scientists use to validate the particle model, provide evidence
for the particle theory, and engage students in validating
the particle model. These factors are likely to lead students
(and teachers) to think that the unit is building a case
for the particulate ideas, although nothing in the Teacher's
Edition explicitly makes this claim or states that this
is the intent. However, the sketchy presentation of evidence
for the particle model and the misrepresentation
of the nature of science in unit 2 make it doubtful that
either of these goals will be achieved by students. It is
unlikely that the unit will enable students to understand
and support the particle model with evidence, explain that
it is scientifically valid, or explain "how we know" that
matter is particulate. In Chapter 10:
Using Scientific Models to Answer Questions, students are to determine the
contents of a mystery box (which they never see directly) by gathering evidence
indirectly. The student text compares, and asks students to compare, the processes
they use in the Mystery Box activity with the processes scientists use to
validate the particle model (pp. 192s, 196-198s, 241s [question 2], 241at
[response to question 2]). Reference is made to the fact that scientists have
gathered abundant evidence in support of the particle model, but that evidence
is not developed or presented in any meaningful way in the student text. For
instance, the Rutherford scattering experiment is presented in such sketchy
detail that students would be unable to weigh or interpret the evidence
(pp. 197-198s). Moreover, Rutherford's experiment (which indicated
that there was space within atoms) is used to support the case for there being
space between atoms: The student text introduces a definition of what
makes models scientific: "[M]odels are not considered scientific models unless they can
explain many, if not all, of the observations that scientists make when conducting
related investigations" (p. 200s). Then, students are asked to use the idea
that "matter is made of particles" to explain three phenomena (relating to
evaporation of water, thermal expansion of gases, and increased rate of diffusion
at higher temperatures). Based on this, students are asked to decide how scientific
the particle model is: "If you can explain all of your observations using
the particle model, then you are verifying that the particle model is a valid
scientific model" (p. 201s). This is a limited
criterion for determining the validity of scientific models (and hence the
validity the particle model), in that it does not encompass such issues as
examining whether the model fits well with other models, whether it predicts
new observations, and how it compares with other explanations of the same
observation. (In chapter 11, the material corrects this narrow premise by
introducing the idea of predictive power in the Gloop
Activity [pp. 218-224] and then by including a section on the falsifiability
of scientific models [pp. 224-230]. However, by this point in the text, most
of the activities regarding "particle" ideas have been completed under the
faulty premise and are not reconsidered in light of these new criteria.) The
activity also suggests, inappropriately, that one can verify that the particle
model is a valid scientific model based on such a small number and variety
of observations. Further, the material
asks students to explain complex phenomena such as evaporation
without their modeling explanations of simpler phenomena
and before they have been introduced to aspects of the model (such as particle motion
and forces holding particles together) that are necessary to
explain these phenomena. This approach risks students concluding
that the particle model is not a scientific model
because they cannot explain the observations using
the model. Although students are asked to revise their explanations
of these phenomena after they have been introduced to the
relevant aspects of the model, they are not asked to reevaluate
the validity of the particle model at that time (p. 207s).
Even if they were and did so, the approach would still inaccurately
represent the scientific process. A logical sequence should
show that the model has success in explaining some
phenomena before showing that it cannot explain other phenomena;
otherwise, why revise (p. 205t) and not discard the model?Firing marbles at an unseen
target is similar to experiments that scientists conduct
today to learn about particles. They fire small particles
at materials to see what happens. What happens to those
particles is consistent with the idea that the material
itself is made of small particles. Some of the fired particles
pass through the material, which means there might be empty
space in the material. Some of the fired particles bounce
off at angles (a few even bounce straight back) which means
there are solid parts to the material. So without ever being
able to see the materials directly, we can conclude something
about the characteristics of the materials-that they are made of particles with spaces between them.
Of course the actual experiments that scientists
conduct are not quite as simple as firing marbles at a hidden
target. The particles that scientists fire at materials
are themselves too small to see. Then how do scientists
know that that they are really firing particles at the materials?
They know because the results of such experiments are consistent
with the evidence they have gained from other experiments.
In these other experiments, they have burned, weighed, smashed
and dissolved materials. They have determined how materials
respond to electricity and magnets. The one thing they cannot
do is look directly inside a material to see whether or
not it is really made up of particles. Yet the results of
all the experiments scientists can do are consistent with
the idea that materials are made up of particles.[pp. 197s-198s]
Chapter 10: Using Scientific Models to Answer Questions and Chapter 11: Using Models to Test and Predict build up to the particle model by giving students pieces of it over time, thus appearing to provide a sequence of encounters with the key ideas that grow in complexity. However, the phenomena that students are asked to relate to the particle model are quite complex from the beginning. For example, in chapter 10, the first phenomenon students are asked to explain involves the evaporation of water from a water-food-coloring solution (pp. 202s, 206−207s).
Although students are asked repeatedly to use the particle model to explain a variety of observations, no explanations are presented in the student text, and the teacher's notes often point out that "[w]hat the teams come up with is not nearly as important as the process they use. Did they base their predictions on their models? Did they appropriately revise their models to account for new observations?" (pp. 221-222t). As a result, although students could tie together these experiences to the key ideas, the textbook does not tie them together for the students, nor does it instruct the teacher to do so.
Ancient explanations for properties of matter are described in some detail (for example, there are several examples of definitions using the Greeks' four elements: air, earth, fire, and water [pp. 186-188s]). However, these ancient explanations are never connected to the key ideas in terms of how they are similar and how they differ.
A strong connection is made between the key ideas and the role of models in science. For example, the teacher's notes state that "[t]his chapter begins a unit that will focus on the importance and use of scientific models. We use the particle theory of matter as a vehicle for students to study the development and use of scientific models." (p. 163at). However, as noted above, because of the equal or greater emphasis on building and testing models, there is the risk of some teachers and students losing sight of the particle theory of matter. So, although the connection is strong, it may work against students' understanding of the kinetic molecular theory. (This view was not shared by one of the review teams, which observed: "Particularly well done are the connections to ancient explanations for the properties of matter and to the concept of a scientific model. The material intentionally restricts connections to many relevant ideas and perhaps is overly restrictive.")
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 or inaccurate language is problematic in text materials, as well as 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 them evaporates," and "draw what happens when the particles change state" (emphasis added) imply inaccurately that the particles themselves change state (melt, evaporate, etc.).
