| 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. |
What would happen, he [Democritus] wondered, if you should cut a piece of iron into smaller and smaller pieces until you could no longer see it? Democritus hypothesized that eventually you would end up cutting the iron into such a small piece (or particle) that it could no longer be cut. Democritus called these tiny particles “atoms.”… Democritus was correct in determining that all matter is composed of atoms…. [p. 6s]
The accompanying teacher’s notes suggest an activity in which students make any object they want using as building blocks popped popcorn and glue or toothpicks, compare the variety of objects they created, and draw an analogy between the popcorn and the atoms. Teachers are to point out that atoms are the building blocks of the universe and that all matter consists of atoms (p. 6t). In a subsequent activity, the statement that “All matter is made up of atoms” leads into a paragraph that explains the transitions from solid to liquid to gas at a microscopic level (p. 20s) and, later, to an activity that is intended to illustrate that atoms exist, even though one cannot see them (pp. 38-39s) (for a critique of this activity, see Building a Case below). Finally, in the context of discussing the structure of the atom, the material mentions that “John Dalton…proposed in 1803 that each chemical element is composed of single building blocks called atoms” (p. 40s). Accompanying teacher’s notes suggest that students write a script for a discussion of atomic theory between the Greek philosopher Democritus and the English chemist John Dalton (p. 40t).
No attempt is made to contrast the atomic theory to naive theories (e.g., 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.
Idea
c: Atoms and molecules are perpetually in motion.
Idea
d: Increased temperature means greater molecular motion,
so most substances expand when heated.
In Using Energy, the student text defines temperature
as “a measure of the average kinetic energy of the
particles that make up an object” (p. 16s). The material
uses the idea that temperature is linked to the energy of
each particle to distinguish the concepts of thermal energy
and temperature. In explaining thermal expansion and changes
of state, the text uses the simpler idea that increased
temperature means greater 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.
Nearly all parts of this key idea are presented. The three
exceptions are that the student text states that particles
of solids move back and forth only slightly, but it does
not say explicitly that the particles vibrate in all directions;
that a gas takes the shape of its container, but not that
its molecules spread evenly through the spaces they occupy;
and that the molecules of a gas move very rapidly and are
free of one another, but not that they move in all directions
and interact during collisions (Changes in Matter, p. 20s).
Most of the parts of this idea are addressed in brief statements
in both Changes in Matter and Using Energy in the context
of describing states of matter and changes of state. In
Changes in Matter, the different arrangement of the particles
in solids, liquids, and gases is illustrated with a drawing
(p. 20s); in Using Energy, the different arrangement and
motion of the particles in solids, liquids, and gases are
illustrated with an analogy (p. 37s). The material rarely
links the arrangement, motion, and forces between particles
to the properties of solids, liquids, and gases in either
text or activities.
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. Later, the student text includes some examples of evaporation
but does not link them explicitly to the molecular explanation
(Using Energy, p. 38s). The material addresses the processes
of boiling, condensation, and sublimation, but not at the
molecular level (Using Energy, p. 38s). Although freezing
is not dealt with directly, the text does mention that liquids
change to solids at “the freezing point” (Using Energy, p. 38s). Neither Using Energy nor Changes in Matter
contains information about dissolving at the molecular level
(there is some discussion of solutions, mixtures, and alloys,
but not at the molecular level).When solids gain thermal energy, their molecules
or atoms move faster. They move a little farther apart but
stay in their patterns…. The state of matter depends
on its temperature. At cold temperatures, almost all materials
are solids with molecules arranged in orderly patterns….
When forces holding molecules together can’t hold
them in orderly arrangements, the molecules stay close together
but begin to change positions. Their positions and movements
become more disorderly, and they become liquids….
At higher temperatures, the thermal energy in the particles
overcomes the forces holding them together and they move
much farther apart. [p. 37s].
In an activity in Using Energy, the material attempts to connect observations to the idea that greater temperature means greater molecular motion. However, the statement at the beginning of the activity misleads students. It reads: “In this activity, you will perform an experiment that will let you discover this relationship [between particle motion and temperature]” (p. 14s). Feeling the heat in a wire bent 15 times or in a wood block rubbed 50 times with sandpaper or measuring an increase in temperature when sand particles are jostled (pp. 14-15s) is unlikely to lead to the “discovery” of the relationship between temperature and molecular motion. Hence, students are more likely to be confused than convinced.
In general, students do not encounter the kinetic molecular theory in progressively higher levels of sophistication. On the contrary, ideas are used without being introduced explicitly, or they are repeated (rather than being returned to precisely or extended clearly to new contexts). For example, the presentation of changes of state in Changes in Matter (pp. 18-19s), relies on the idea that particles are in motion; however, this idea is not introduced specifically in this book. And Using Energy (pp. 36-39s) includes a section on phase changes without linking it to the very similar presentation of changes of state in Changes in Matter.
In both Using Energy and Changes in Matter, the kinetic molecular theory is connected to some related ideas. For example, the motion of atoms is associated with the idea that heat energy is in the disorderly motion of the atoms and with heat transfer by collisions of atoms.
In the introductory pages (pp. T8–T9) of the Teacher's Planning Guide, seven major themes (systems and interactions, scale and structure, stability, energy, evolution, patterns of change, and models) are linked to each unit in the program. A statement on page T8 claims that “Key concepts revolve around seven major themes so students experience and make sense of the connections in science.” The secondary theme used in Changes in Matter is scale and structure. However, the theme of scale and structure is not described, nor is it specified how the unit is connected to that particular theme. Hence, it is not clear how the material helps students to make sense of the connections in science. The feature “Theme Connection,” which appears in the teacher’s notes for each lesson, provides little guidance to teachers. For example, according to the Theme Connection that accompanies the section on changes of state in Changes in Matter: “The theme linking some important concepts in this unit is Scale and Structure. The behaviors of atoms and molecules in solids, liquids, and gases cannot be directly observed but they can be modeled using a clear jar three-quarters filled with plastic beads (or popcorn kernels) to represent water molecules” (p. 21t). This note is unlikely to help students’ comprehension in that it fails to specify both how the fact that the behaviors of solids, liquids, and gases cannot be observed directly but can be modeled relates to scale and structure, and how the behaviors of atoms and molecules in solids, liquids, and gases can be modeled using a clear jar three-quarters filled with plastic beads.
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. 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.).
