In evaluating the content of the individual middle grades science programs covered in this document, the review, or evaluation, teams have determined whether there is match between each program’s coverage of certain Earth, life, and physical science topics and a corresponding set of key ideas prepared by Project 2061. The ideas have been drawn from both Benchmarks for Science Literacy (American Association for the Advancement of Science, 1993) and National Science Education Standards (National Research Council, 1996). Each of the three idea sets has been selectively annotated to provide users with additional guidance.
Key Earth Science Ideas
This set of key ideas focuses on the changing surface of the Earth and the geologic events and processes that constantly shape and reshape it. The idea set is based on chapter 4, section C of Benchmarks and Earth and Space Science Content Standard D of National Science Education Standards.
Earth-shaping processes range from the abrupt, readily observable processes—such as volcanic eruptions and earthquakes—to the very slow, barely visible ones—such as mountain building and canyon formation. While Benchmarks postpones the treatment of plate tectonics until grades 9–12, National Science Education Standards and most state frameworks recommend that it be taught in middle school. In the absence of cognitive research related to this set of key Earth science ideas, teaching it in middle school might be feasible. Since all curriculum materials include the concept of plate tectonics by grade 8 (which is the last encounter most students have with Earth science), ideas about plate motion and the geologic events and land features that result are included in this idea set.
Idea a: The surface of the Earth is changing continually.
This idea focuses on the ever-changing nature of the surface of the
Earth, as opposed to the seeing the Earth’s surface as static
or unchanging. Various processes that shape and reshape the Earth’s
surface—for example, erosion, plate motion, and earthquakes—can
illustrate this continual change. To get credit for this idea, the
curriculum material needs to refer not only to changes that have happened
in the past, but also to the idea that the Earth’s surface is
still changing and will likely change in the future. Descriptions
of recurring events, such as earthquakes or volcanic eruptions, that
do not make explicit that these processes result in the continual
change of the face of the Earth, are not aligned to this key idea.
Idea b: Several processes contribute to changing the Earth’s
surface.
This idea focuses on the variety of specific factors that shape the
surface of the Earth. To help students appreciate this variety, the
curriculum material needs to present more than one Earth-shaping process
and preferably compare a variety of processes or explicitly call students’
attention to the generalization in the idea. The emphasis should be
on the effect each process has on the Earth’s surface, rather
than the mechanism or other aspects of each process. For example,
describing only the destructive nature of earthquakes will not constitute
a match to this key idea unless the material refers to the subsequent
change to the Earth’s surface. Since change is the key here,
photographs, diagrams, or explanations that depict before and after
scenes (for example, the effects of glaciers or waves) are credited
as instances of this idea, whereas photographs of only a single time
point are not. Ideally, the curriculum material should make clear
that more than one process may operate simultaneously on a particular
landscape (such as erosion and mountain building).
Idea c: The processes that shape the Earth today are similar
to the processes that shaped the Earth in the past.
This idea states the assumption that makes it possible to infer something
about past geologic events and their relationship to current Earth
features. The basis for this assumption is that the laws that govern
the physical environment, such as gravity, have not changed. Ideally,
the curriculum material not only states that geologists believe that
the same processes that shape the Earth today have been at work in
the past, but also makes reference to specific processes (such as
rivers flowing downhill). The idea that Earth-shaping processes might
have worked at different rates in the past goes beyond what is expected
here.
Idea d: Some of the processes are abrupt, such as earthquakes
and volcanic eruptions, while some are slow, such as the movement
of continents and erosion.
This idea focuses on the time scales of various Earth-shaping processes.
A complete treatment of this key idea includes both abrupt and slow
changes to the surface of the Earth, as well as the explicit presentation
of the generalization in the idea regarding the vast range of time
frames of various processes—by means of text, discussion of
the time frames of these processes, or comparison of rates. Discussion
of various processes in isolation without explicit reference to the
range of rates is inadequate.
Idea e: Slow but continuous processes can, over very long
times, cause significant changes on the Earth’s surface.
The focus of this idea is that slow, seemingly unnoticeable Earth-shaping
processes can make significant changes to the surface of the Earth
if they occur over long periods of time. Alignment to this idea requires
explicit treatment of significant changes in the Earth’s surface
(such as the rise of mountains or the movement of continents) that
result from slow rates of change over very long time frames. Simply
mentioning that some processes are slow, or that some processes have
occurred over millions of years, is insufficient. To get credit for
this idea, the curriculum material needs to refer to specific rates
(for example, erosion of a cliff occurring at a rate of several centimeters
per year), and, ideally, helps students appreciate how multiplying
slow rates by long time periods can result in large changes.
Idea f: Matching coastlines and similarities in rocks and
fossils suggest that today’s continents are separated parts
of what was a single vast continent long ago.
This idea states evidence for the movement of continentals—matching
coastlines, similarities in rocks, similarities in fossils—and
the conclusion drawn from it—that today’s continents are
separated parts of what was a single vast continent long ago. To get
credit for this idea, the curriculum material does not need to address
all three observations that are included specifically in this idea.
However, it does need to present the idea in its historical context,
that is, not only to describe the evidence but also to indicate that
this is the evidence that led scientists to the idea that continents
move. The material should also explain how the different pieces of
evidence support the theory of continental movement, and, ideally,
it should point out that continents probably moved before (and not
only after) the formation of the super continent Pangaea. More recent
evidence, such as magnetic data from the ocean floor, goes beyond
the scope of this key idea.
Idea g: The solid crust of the Earth consists of separate
plates that move very slowly, pressing against one another in some
places, pulling apart in other places.
This idea states, in simple terms, the basic idea of plate tectonics.
To get credit for this idea, the curriculum material needs to address
all three aspects of the idea: (1) the solid crust of the Earth consists
of separate plates; (2) these plates constantly move at a slow pace
in different directions; and (3) as a result of plate motion, the
plates interact with one another. While the material should make the
explicit connection between plates and continents (for example, by
stating that continents sit on top of the plates), the possible causes
for plate motion go beyond this idea.
Idea h: Landforms and major geologic events, such as earthquakes,
volcanic eruptions, and mountain building, result from these plate
motions.
This idea links observable phenomena, such as geologic events and
landforms on the Earth, to the movement of plates, stating that there
is causal relationship. To get credit, the curriculum material should
both explain current phenomena (for example, why Japan and the West
Coast of North America are prone to earthquakes) and use the theory
of plate tectonics to predict phenomena (for example, where on the
Earth new mountains are likely to form).
This set of key ideas focuses on matter and energy transformations in living systems, including organisms and ecosystems. It is based on chapter 5, section E of Benchmarks and Life Science Content Standard C of National Science Education Standards.
The topic of matter and energy transformations can be treated at either the substance or molecular level in grades 6–8. At the substance level, matter transformations are seen as changing inputs into outputs—for example, carbon dioxide and water (inputs to photosynthesis) are transformed into sugars and oxygen (outputs). At the molecular level, matter transformations are seen in terms of the rearrangement of building blocks. In an evaluation, the curriculum material should first be examined to see which of the two levels it appears to emphasize and then be analyzed with that level in mind.
Idea a: Food (for example, sugars) provides molecules that
serve as fuel and building material for all organisms.
This idea is fundamental for student understanding of the other key
life science ideas, especially because the everyday meaning of the
term “food” is inconsistent with its biological meaning.
This idea goes beyond the idea that organisms need food to
grow or for energy. It can be thought of at either the substance or
molecular level. At the substance level, food is the source of both
the building materials that makes it possible for organisms to increase
in mass and the fuel that provides the energy needed to carry out
life functions (for example, add new cells, convert inputs to outputs).
At the molecular level, food provides the molecular building blocks
that are assembled into body structures or used as fuel. Since this
idea is fundamental to the other key ideas, the level at which it
is treated determines what is possible for subsequent ideas. Partial
credit is given to curriculum materials that treat either the matter
or the energy side of the story, but obviously, it is difficult for
materials to convey the matter and energy transformations story without
both parts of this idea. To receive full credit, the material needs
to make the generalization (in text and concrete examples) that all
organisms—not only humans—get their building materials
and energy from food.
Idea b: Plants make their own food, whereas animals obtain
food by eating other organisms.
The essence of this idea is the contrast between plants, which make
their own food, and animals, which do not, and hence must obtain food
by eating other organisms. Alignment requires that the contrast be
made explicitly.
Idea c: Matter is transformed in living systems.
The essence of this four-part idea is transformation (as opposed to
just naming the reactants and products). It must be explicit that
something is being transformed (that is, converted, made into, or
changed) into something else.
Idea c1: Plants make sugars
from carbon dioxide (in the air) and water.
At the substance level, carbon dioxide and water are transformed into
sugar (but not any of the intermediate steps). At the molecular level,
the carbon, hydrogen, and oxygen atoms in carbon dioxide and water
are rearranged to form sugars.
Idea c2: Plants break down
the sugars they have synthesized back into simpler substances—carbon
dioxide and water—and assemble sugars into the plants' body
structures, including some energy stores.
This idea describes the three possible fates of the sugars (sugar
molecules) that plants make: (1) plants can transform some of the
sugars back into carbon dioxide and water, (2) they can assemble them
into body structures, or (3) they can store them for later use. The
curriculum material can earn partial credit for presenting one or
two of these fates, but to do so, it needs to be explicit in their
treatment of transformation of matter. Observations of respiration
in germinating seeds, for example, that focus on gas exchange and
not on the breakdown of sugars do not align with this idea.
Idea c3: Other organisms
break down the stored sugars or the body structures of the plants
they eat (or in the animals they eat) into simpler substances and
reassemble them into their own body structures, including some energy
stores.
This idea describes the possible fates of consumed food in organisms
that don’t make their own food. Food is broken down (during
digestion) into sugars (and other building blocks) and the sugars
can be further broken down to carbon dioxide and water; the building
blocks can be reassembled into the body structures of the consumers;
some of the reassembled building blocks (e.g., fat) can serve as storage
forms for later use. The curriculum material can earn partial credit
for presenting one or two of these ideas. To receive full credit,
it should go beyond describing a single organism—such as humans—to
the generalization that all consumers carry out these processes.
Idea c4: Decomposers transform
dead organisms into simpler substances, which other organisms can
reuse.
This idea describes the role of decomposers in returning carbon (and
nitrogen) to the environment so that they are available for use by
other organisms. Complete alignment requires that the material make
the notion of reuse explicit. The curriculum material should
be explicit about matter transformation, although partial credit is
given for statements about the “breakdown” of dead organisms.
Idea d: Energy is transformed in living systems.
The common feature of this three-part idea about energy transformations
is that one form of energy is being converted into other forms—for
example, light to chemical energy, chemical energy to chemical (or
mechanical or electrical) energy and heat.
Idea d1: Plants use the
energy from light to make "energy-rich" sugars.
This key idea makes explicit the transformation of light energy into
chemical energy (or “energy rich” sugar molecules). Curriculum
materials must go beyond stating that energy is used to make
sugars or to convert carbon dioxide and water into sugars (because
such statements could give the impression that energy is used
up in the process). At the middle school level, it is acceptable
to leave vague where the energy actually is. For example, the material
does not need to specify that the energy is stored in the configuration
of atoms.
Idea d2: Plants get energy
by breaking down the sugars, releasing some of the energy as heat.
This idea describes the two fates in plants of the energy they store
in sugars. As plants break down the sugars, they can harness some
of the energy stored in sugars and they give some off as heat. Both
fates are needed for a full match. The focus here is on the energy
transformations; it does not matter whether matter is treated in terms
of molecules or substances. However, just indicating that organisms
need a source of energy to stay alive and grow is a less sophisticated
idea.
Idea d3: Other organisms
get energy to grow and function by breaking down the consumed body
structures to sugars and then breaking down the sugars, releasing
some of the energy into the environment as heat.
This idea describes the two fates of the energy stored in the food
consumed by other organisms. As they break down the sugars, the organisms
harness some of the energy stored in sugars and they give some off
as heat. Both fates are needed for a full match. The focus here is
on the energy transformations; it does not matter whether matter is
treated in terms of molecules or substances. However, as with Idea
d2, just indicating that organisms
get energy from food is a less sophisticated idea. To receive
full credit, the curriculum material should go beyond describing a
single organism—e.g., humans—to the generalization that
all consumers carry out these processes.
Idea e: Matter and energy are transferred from one organism
to another repeatedly and between organisms and their physical environment.
This idea connects the isolated examples of matter and energy transformations
in individual organisms to their repeated flow through ecosystems.
The curriculum material may use the carbon cycle and/or the nitrogen
cycle, but it is not necessary. A quite acceptable story could explain
that as organisms consume other organisms, the food (that contains
both matter and energy) is passed from the consumed organism to the
consumer and is transformed in the process. Matter that leaves the
bodies of organisms and returns to the environment (for example, as
carbon dioxide) may be returned to living organisms through the actions
of plants. However, to receive full credit, the material needs to
make explicit that matter passes through food webs repeatedly—that
is, over and over again.
This set of key ideas focuses on basic assumptions of the kinetic molecular theory and their use in explaining thermal expansion and changes of state. It is based on chapter 4, section D of Benchmarks and Physical Science Content Standard B of National Science Education Standards.
Idea a: All matter is made up of particles called atoms and
molecules (as opposed to being continuous or just including particles).
This idea has two aspects: (1) that matter is particulate (rather
than continuous), and (2) that the particles (atoms or molecules)
are the matter (rather than the commonly held incorrect idea
that particles [atoms or molecules] are contained in matter).
In principle, the curriculum material could teach this idea in terms
of particles, without making the connection to atoms and molecules.
In such cases, the content analysis part of an evaluation report should
note that the material addresses this idea in terms of particles rather
than in terms of atoms and molecules. If the material introduces the
ideas in terms of particles and only later makes the connection to
atoms and molecules, the coherence segment of the content analysis
part should examine how well the material links atoms and molecules
to particles. The treatment of subatomic particles goes beyond this
idea.
Idea b: These particles are extremely small—far too
small to see directly through a microscope.
The idea is that atoms and molecules are far too small to see through
a light microscope. Images of atoms obtained with scanning
tunneling microscopes and the actual size of atoms and molecules go
beyond this idea.
Idea c: Atoms and molecules are perpetually in motion.
The idea is that atoms and molecules of all matter are perpetually
in motion. A complete content match to this idea would make clear
that molecules of solids, liquids, and gases are in motion.
Idea d: Increased temperature means greater molecular motion,
so most substances expand when heated.
This idea has three components: (1) the relationship between temperature
and molecular motion; (2) thermal expansion of solids, liquids, and
gases; and (3) the connection between changes in the motion of molecules
(with increased temperature) and thermal expansion. The link between
increased temperature and average energy of motion of molecules (a
more sophisticated idea) does not serve as a basis for this analysis.
The curriculum material should neither be held accountable for presenting
the link between increased temperature and average energy of motion,
nor penalized for including it.
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.
This idea focuses on the differences in proximity, arrangement, motion,
and interaction of atoms and molecules of solids, liquids, and gases.
The nature of interactions between and within molecules (for example,
types of bonds) goes beyond this idea.
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.
This idea focuses on the molecular explanation of changes
of state. Descriptions of changes of state only in terms of heat transfer
are not sufficient for alignment. Descriptions of phase diagrams go
beyond this idea.