Investigating
Students’ Ideas
About the Flow of
Matter and Energy
in Living Systems
by Melanie Taylor, Kimberley Cohen,
R. Keith Esch, and P. Sean Smith
“There is a good deal of evidence that learning is enhanced when teachers pay attention to the knowledge
and beliefs that learners bring to a learning task, use
this knowledge as a starting point for new instruction, and monitor students’ changing conceptions as
instruction proceeds.”
—Bransford, Brown, and Cocking 2000
“Plants use fertilizer as food.”
“Plants need food to help animals.”
“Food goes to different parts of the body and gets
used up; some gets extracted and changed.”
“Animals don’t store food, except in cupboards.”
“Plants use food for photosynthesis and energy.”
“All the food leaves the body after it is eaten; none
stays in.”
“The wood of a tree is made from the nutrients absorbed through its roots.”
26
SCIENCE SCOPE
I
t is fascinating to listen to middle school students talk about food for plants and animals and
how that food is used. Some students describe
ideas that are essentially correct. Some comments suggest that students are familiar with the content, but their understanding is incomplete or includes
inaccuracies. Finally, some students have little understanding of the content; however, they use their own
experiences to reason logically and generate their own
ideas about the content. Beyond just listening, uncovering students’ initial ideas and attending to how those
ideas change over a unit of instruction are important
steps to ensuring that students learn scientifically correct ideas. In this article, we describe strategies for
eliciting student thinking, common responses to elicitation prompts, and implications for moving students’
thinking forward.
Eliciting students’ ideas
As part of a project designed to develop a science
assessment for middle school students, researchers
from Horizon Research Inc. (HRI) interviewed middle school students regarding their ideas about food,
energy, and plant and animal growth. The purpose of
the interviews was to uncover common, incorrect student ideas that could serve as distractors for multiplechoice test questions. Before conducting the inter-
FIGURE 1
views or writing any test questions, HRI researchers,
working from Benchmarks for Science Literacy (AAAS
1993) and the National Science Education Standards
(NRC 1996), defined the content of the assessment.
The broad student learning goal for this content area,
along with a number of more narrowly defined corresponding subideas, is presented in Figure 1.
Middle school students often hold ideas that are tied
to everyday use of terms that also have more specific
meanings in science. In particular, “food” may be generally thought of as any material an organism takes in
from its environment. In the context of the flow of matter and energy, however, “food” is specifically defined
as material that provides chemical energy and matter
for organisms’ functions and growth. Materials that are
taken in by an organism but do not provide both matter and energy are not considered food by scientists.
The main science ideas included in this content area
can be represented diagrammatically, as seen in Figure
2. Plants make their food using light, carbon dioxide,
and water, and animals consume plants to get food. The
labeled arrows indicate the relationships among major
conceptual components of this content. This concept
map also highlights the fundamental distinction that
matter is continuously recycled while energy flows one
way through living systems.
After clarifying the content by defining ideas,
subideas, and their interrelationships, we crafted open-
Defining and clarifying the content
The learning goal: Food provides molecules that serve as fuel and building materials for all organisms. Plants use
the energy in light to make sugars from carbon dioxide and water. This food (sugars) can be used immediately for fuel
or materials, or it can be stored for later use. Organisms that eat plants break down the plant structures to obtain the
materials (molecules) and energy they need to survive. These organisms can then be consumed by other organisms.
Helping students achieve understanding of this learning goal involves attending to each of several subideas within
this larger idea. The identified subideas include the following, although they could be broken apart even further:
•
•
•
•
•
•
•
Food (e.g., sugar) serves as both fuel (i.e., energy source) and building materials (i.e., matter) for an organism.
Using light energy, plants make their own food (i.e., sugars) from carbon dioxide (in the air) and water.
Plants transform light energy into chemical energy in sugars made by the plants.
Humans and other animals acquire food by consuming plants or other animals that have consumed plants.
Organisms grow by breaking down food into simpler substances that they reassemble into other substances that become part of new or replacement body structures.
Organisms break down energy-rich food (e.g., sugars), using oxygen, into simpler substances with less energy (e.g., carbon dioxide and water), releasing energy in the process.
If not used immediately as fuel or building material, food can be stored for later use by plants and animals. In animals, but not in plants, food can also be eliminated from the body as waste.
A p r i l / M a y 2 012
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investigating students’ ideas About the flow of matter and energy
ended questions to elicit students’ ideas about these
concepts. Guiding this development were preliminary
lists of misconceptions that HRI developed based on the
results of a literature search, as well as the experiences
of the research team in teaching life science. Questions
covered the whole range of ideas within the learning
goal; a few are included here:
• Let us say that you were trying to explain what
food is to a small child. What would you say to help
this child understand what food is?
• Why do plants need food? What do they do with it?
Do plants use all the food they have right away? If
they do not use all the food, what happens to the
food that is not used?
• Where do animals get their food? For what do
animals use food? Do animals use food differently
from the way plants use it?
• Do you think plants need energy in the same way
humans and other animals need energy? Why do
plants need energy? How do they use it? Where do
plants get that energy?
We interviewed 11 middle school students individually for about an hour each. Most students had
previously received some instruction in this content.
Analysis of the interviews included a focus on identifying misconceptions and incomplete ideas that students
have for this content. The misconceptions identified
can be used to formulate effective distractors in multiple-choice questions (for more information on writing
student assessment items, see Taylor and Smith 2009).
FIGURE 2
Concept map of interactions
involving the flow of matter
and energy in living systems
Where food comes from
How food is used
Consume
Animals
Matter
Consume, store,
and use (respire)
Molecules broken
down and reassembled
Food
Consume
Molecules
broken down
Make, store, and
use (respire)
Plants
Energy
Release
Use
Carbon dioxide,
light, and water
28
Decomposition (matter
moves in cycles)
Facilitates
release of
Oxygen
SCIENCE SCOPE
Some “lost” as thermal
energy to system (energy
flows in one direction)
Results
Figure 3 includes many examples of student misconceptions about the flow of matter and energy in living
systems, which were either identified or confirmed
through interviews. In some cases, students expressed
ideas that fit with everyday usage of common terms but
were not consistent with a science-based understanding of this content—for example, the idea that “plants
capture sunlight.” Whereas many of the ideas included
on the preliminary lists of misconceptions surfaced in
interviews, several additional ideas emerged. For example, many students did not know the definition of
food as being both a source of energy and a source of
material for growth. It was also common for students to
think that water, rather than the sugars that plants make
through photosynthesis, is food for plants. The water-isfood-for-plants idea is evident in this student’s statement:
“Desert plants might store some food. Rainforest plants
might use it all right when they get it. The roots adapt to
getting the rain.” Students who think water is food also
tend to think incorrectly that food is absorbed through
plant structures, such as the roots, instead of being made
inside the plant. One student shared, “Roots absorb food
through cells, and it goes to the petals where [the plant]
stores water. It restocks water when it runs out.”
Students had interesting ideas about how organisms
grow and the energy they need. Many thought that all
the building material (i.e., matter) for growth exists inside
an organism before growth occurs; the existing matter
simply “stretches” or “spreads out.” Some students considered the energy needed by animals to be different
somehow from that needed by plants. Others thought the
energy was used for different purposes; for example, one
student said, “Plants need energy [only] to grow. People
need energy [only] to move.”
Making sense of results
Although many misconceptions were apparent during
the interviews, it was clear that students often drew from
their own knowledge base to construct logical, albeit incorrect, answers. Over the last few years, the terms misconception (which we have adopted here), prior conception, naïve conception, and others have come in and out
of favor in education circles. There is a lack of consensus
on what these terms mean, as well as on their relative
importance in teaching and learning. There is agreement, however, that students come to science class not
as empty vessels but rather with their own ideas about
the world. There is also agreement that some misconceptions are strongly held by students and quite resistant
investigating students’ ideas about the flow of matter and energy
FIGURE 3
Misconceptions related to the flow of matter and energy in living systems
(continued on page 30)
Subidea: Food (e.g., sugar) serves as both fuel (i.e., energy source) and building materials (i.e., matter for
an organism.
Related misconceptions
Corresponding correct ideas
Food is a requirement for growth, but the resulting matter
generated by growth comes from another source.
Matter used for growth comes from food that organisms
use.
Food is anything that goes into an organism—carbon
dioxide, water, sunlight, oxygen, etc.
Only matter that is used for growth and energy is food.
Food is anything edible.
Nonfood materials can be eaten, but that does not
mean they are food.
Food is energy.
Energy is released when food is broken down.
Food cannot be liquid.
Food can be a liquid (e.g., a milkshake).
Subidea: Using light energy, plants make their own food (i.e., sugars) from carbon dioxide (in the air) and water.
Related misconceptions
Corresponding correct ideas
Plants “eat” (i.e., ingest) food substances, including fertilizer.
Plants make their own food internally.
Roots are the feeding organs for plants.
Roots absorb water and minerals, not food.
Plants use oxygen in photosynthesis.
Plants release oxygen in photosynthesis.
Plants need only soil, water, and sunlight to live (no gases).
Plants need gases (e.g., carbon dioxide) to live.
Plants have multiple sources of food.
Plants rely on photosynthesis for food.
Light is a food or a reagent in photosynthesis.
Light energy is used in photosynthesis.
Carbon dioxide cannot become part of matter because
gas does not have weight.
Gases do have weight and are matter.
Subidea: Plants transform light energy into chemical energy in sugars made by the plants.
Related misconceptions
Corresponding correct ideas
Light energy is a necessary “ingredient” for photosynthesis to take place, and it is “used up” like carbon dioxide
and oxygen.
Light energy drives the process of photosynthesis, but
the light is not consumed.
Light is a “facilitating agent”—just as it helps us read a
book, it helps plants make food.
Light is changed when used in photosynthesis because
it supplies energy.
Light energy disappears, and sugar energy is a “new,”
unrelated energy.
Energy in light is transformed into energy in sugars.
Light has energy but sugars do not.
Sugars have stored chemical energy.
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investigating students’ ideas About the flow of matter and energy
FIGURE 3
Misconceptions related to the flow of matter and energy in living systems
(continued from page 29)
Subidea: Plants transform light energy into chemical energy in sugars made by the plants.
Related misconceptions
Corresponding correct ideas
Plants convert energy from the Sun directly into matter
(e.g., food or body structures).
Light energy is used to drive reassembly of existing
matter (e.g., carbon dioxide and water) into food or
body structures.
Sunlight is only one of many energy sources for plants;
others include soil, minerals, water, air, and wind.
Soil, minerals, water, air, and wind can affect plant
health but do not supply energy to plants.
Subidea: Humans and other animals acquire food by consuming plants or other animals that have consumed plants.
Related misconceptions
Corresponding correct ideas
Because carnivores eat only animals, they could survive
if no plants existed.
Carnivores could not survive if no plants existed.
Plants “want” to be eaten or to make food for animals.
Plants make food for their own use; although animals do
consume them, the plants do not have desires or intentions.
Subidea: Organisms grow by breaking down food into simpler substances that they reassemble into other
substances that become part of new or replacement body structures.
30
Related misconceptions
Corresponding correct ideas
Food helps the growth process along but is not a part of
the result. It is used up.
Matter from food is incorporated into new structures
during growth.
Plants make food from water and air, but it is not transformed into the plant’s body. For example, the mass of a
tree comes from water and soil (ignoring the contribution
of carbon dioxide).
The food that plants make using water and air is used
to make plant structures. Much of the wood mass of a
tree comes from carbon dioxide.
Matter is created or destroyed rather than transformed.
Matter is neither created nor destroyed but changed to
different forms.
Animals, but not plants, break down food into simpler substances that are used for new or replacement tissues or parts.
Both animals and plants break down food into substances that are used for new or replacement tissues or parts.
We get fat by eating fat, which is stored unchanged in our bodies, or by eating too much sugar, which we cannot break down.
Fats and sugars can be broken down to other substances
that are reassembled into materials that are used or stored.
Organisms take in and use some substances and produce others. These are separate events—substances
taken in are not raw materials for the products.
Substances that organisms produce are made from the
substances the organisms have taken in.
SCIENCE SCOPE
investigating students’ ideas about the flow of matter and energy
Subidea: Organisms grow by breaking down food into simpler substances that they reassemble into other
substances that become part of new or replacement body structures. (continued)
Related misconceptions
Corresponding correct ideas
Organisms and materials in the environment are very different types of matter and are not transformable into each other.
The matter of organisms is transformed into nonliving material in the environment as well as into other organisms.
Food is converted directly from matter into energy.
Food cannot be converted directly into energy; when
food is broken down, energy is released.
Subidea: Organisms break down energy-rich food (e.g., sugars), using oxygen, into simpler substances with
less energy (e.g., carbon dioxide and water), releasing energy in the process.
Related misconceptions
Corresponding correct ideas
Matter (food) is transformed into energy rather than into
simple substances.
Matter (food) is transformed into simple substances,
releasing energy.
Plants release oxygen but not carbon dioxide.
Plants release carbon dioxide in the process of breaking down food.
Plants photosynthesize but do not break down food.
Plants photosynthesize and also break down food.
Energy is not transferred from one organism to the next.
When one organism consumes another, energy is transferred.
Water is a source of energy.
Organisms get energy from food, not from water.
Subidea: If not used immediately as fuel or building material, food can be stored for later use by plants and
animals. In animals, but not in plants, food can also be eliminated from the body as waste.
Related misconceptions
Corresponding correct ideas
Plants have digestive tracts—food goes in, waste comes out.
Plants make food internally and do not have digestive tracts.
Organisms store sugars that they consume, not sugars
that are created when they break down food.
Organisms store sugars that are made from materials
produced from food that is broken down.
Sugars are fuel that is used immediately; fat is fuel that is
stored.
Both sugars and fats can be used immediately or stored
for later use.
to instruction and that some represent important steps
toward full understanding of an idea. Even with instruction, it is often difficult for students to let go of these misconceptions and internalize the correct understanding of
the situation (Bransford, Brown, and Cocking 2000). For
example, many interviewed students seemed to think
that fertilizer is food for plants, likely as a result of the
common use of the term plant food to refer to fertilizers.
Students with experience gardening or farming may find
it difficult to understand that all the food used by a plant
is made inside its tissues through photosynthesis.
In other cases, however, students’ misconceptions
about a topic may not be strongly held or resistant to
instruction. In life science, for example, some phenom-
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investigating students’ ideas About the flow of matter and energy
FIGURE 4
Eliciting, analyzing, and addressing students’ conceptions of the flow of matter
and energy in living systems (continued on pages 34 and 35)
Analysis of
student thinking
At some point, you have
probably planted a seed
and watched a plant grow.
What did you do to take
care of the plant? Why
did you do each of those
things?
“I grew tomatoes once. I
watered the tomato plants
and made sure they had
sunlight. Plants cannot
make food unless they
have water and sunlight.”
The student correctly
thinks that plants need
water and light to grow,
but it is unclear from the
response whether the
student understands that
carbon dioxide is also
needed or that other forms
of light are adequate.
A tiny acorn grows into a
small seedling and then
into a large oak tree.
Where does the material
that makes up the tree
come from?
“Most of the material comes from the soil
that the plant sucked in
through its roots.”
The student incorrectly
thinks that plants take in
soil. The student does
not appear to understand
the contribution of carbon
dioxide to the matter that
makes up the tree.
Elicitation
Using light energy, plants
make their own food—in
the form of sugars—from
carbon dioxide (in the air)
and water.
Using light energy, plants
make their own food—in
the form of sugars—from
carbon dioxide (in the air)
and water.
Organisms (including both
plants and animals) grow
by breaking down food
(including sugars made
by plants and sugars
ingested by animals) into
simpler substances that
they reassemble into other
substances that become
part of new or replacement body structures.
32
Typical student
responses
Targeted subideas
SCIENCE SCOPE
investigating students’ ideas about the flow of matter and energy
Strategies to move student thinking forward
Help students understand that both water and carbon dioxide are the raw materials plants need to make their own food.
To demonstrate that plants need carbon dioxide to make sugars, it may be
helpful to compare starch production (an indicator of sugar production because starches are combined sugars) of plants in the presence or absence
of carbon dioxide.
One possible activity: Use three mum plants. Place each plant in a separate,
closed container. For the first mum, increase the amount of carbon dioxide
and then seal the container. For the second mum, absorb some of the carbon
dioxide and then seal the container. Seal the container with the third plant; this
is the control (normal atmospheric levels of carbon dioxide). After 24 hours in
the light, remove leaves from each plant and test for the presence of starch.
The mum in the container with the decreased carbon dioxide should show less
starch production because the plant could not make food as readily (for specific
procedures, see NCOSP 2005).
Although the tree may grow more healthfully in the presence of nutrient-rich
soil, students need to understand that neither the nutrients nor the soil serves
as food for plants. Sharing the historic experiment that investigated whether
soil was food for plants (conducted by Jean Baptiste van Helmont) may be
useful. In this experiment, the amount of soil around a tree did not significantly
decrease over time, but the mass of the tree increased greatly.
Students need to understand that plants make their own food (i.e., sugars)
using light energy from the Sun, carbon dioxide, and water. Much of the mass
of the tree comes from this carbon dioxide. The experiment in the first example
can help students understand the role of carbon dioxide in sugar production.
Although it is not feasible in middle-grade classrooms to observe how water
is combined with carbon dioxide to make sugars, it can be demonstrated that
plants take in water. For example, if the roots of a plant are placed in a sealed
test tube filled with water, the water level will decrease over time.
To demonstrate that light energy is necessary, students could explore the
absence of starch in well-watered plants in a warm, dark room; this would also
suggest to students that thermal energy does not drive photosynthesis, a less
common student misconception.
It is also important for students to know that the sugars made by plants are broken down into simpler substances. These simpler substances are reassembled
to make new plant parts, such as stems, roots, and leaves. At the middle-grade
level, it may be helpful to explain to students that food is broken down in animals and then explain that this also occurs in plants. For example, point out that
food does not remain in an animal in the form in which it was taken in.
ena are too small to observe directly,
making them inaccessible to students.
Because students typically do not
have real-world experience with these
phenomena, getting them to let go of
misconceptions in favor of the correct
concept may not be as difficult as
tackling other misconceptions that are
reinforced by everyday experiences.
For instance, the process of cellular respiration (the breaking down of energyrich foods into simpler substances with
a subsequent release of energy) may
often be confused with breathing, but
students are not as likely to have other
preconceived, strongly held misconceptions related to this process as they
would for a more familiar idea, such as
what is food for plants.
Implications for
instruction
Regardless of whether students have
deeply held misconceptions or simply have incomplete ideas about a
particular topic, it is important that
they have opportunities to express
their thinking (Bransford, Brown,
and Cocking 2000; Minstrell 2003).
Various learning-cycle approaches
to teaching include time for students
to talk about and share their ideas
about the targeted concept. This approach helps students become more
aware of their own thinking while
also giving teachers a chance to learn
what students are thinking. Learning
theory suggests that the intellectual
engagement of students based on
what they already know is crucial for
learning science content. An awareness of their own thinking can enable
students to more easily connect their
new understandings to their existing
knowledge and facilitates the confronting of existing misconceptions
with new science-based understandings (Banilower et al. 2010). Thus,
generating opportunities for concrete
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investigating students’ ideas About the flow of matter and energy
FIGURE 4
Eliciting, analyzing, and addressing students’ conceptions of the flow of matter
and energy in living systems (continued from pages 32 and 33)
Targeted subideas
Elicitation
Organisms (including both
plants and animals) break
down energy-rich food
(such as sugars), using
oxygen, into simpler substances with less energy
(such as carbon dioxide
and water), releasing
energy in the process.
At school, you probably
have a gym class, or maybe you play sports. Where
do you get the energy
you need to participate in
those activities? If you are
tired, what can you do to
get more energy?
If not used immediately
as fuel or building material, food can be stored
for later use by plants and
animals. In animals, but
not in plants, food can
also be eliminated from
the body as waste.
FIGURE 5
Break down
food: provides
energy and
materials for
growth
Plants
34
SCIENCE SCOPE
“You get energy by running. If you get tired, you
can get more energy by
sleeping.”
Analysis of
student thinking
The student seems to be
missing the idea that food
is the source of energy
for organisms. Food is
broken down into simpler
substances, and when this
occurs, energy is released.
Sleep may be perceived
as an energy provider in
and of itself rather than an
opportunity to replenish
energy by the breakdown
of food.
Although it is not clear
from the student’s statement, one inference is that
the student might not understand that food, which
contains energy, can be
stored.
Developing student diagram
for relating plants and animals
to food
Make their
own food
Typical student
responses
Animals
Get food
from other
organisms
consideration of student ideas is important to effective
instruction.
In cases where research on student conceptions
already exists and is available, such as in the area of
force and motion, student feedback may confirm that
their ideas are very much aligned with the research.
In the case of topics such as flow of matter and energy,
informal research of the kind described in this article
may provide teachers with additional insights into what
students might be thinking. In many other topic areas,
however, even informal research on student thinking
has not yet been done, making it more difficult for
teachers to recognize the ideas they are trying to elicit
from students.
Eliciting students’ ideas and then responding in ways
that promote student learning are at the heart of teaching,
but they are by no means easy tasks. Part of the problem
lies in difficulties associated with constructing elicitation
investigating students’ ideas about the flow of matter and energy
Strategies to move student thinking forward
Students need to understand that food is the source of both building materials and fuel (i.e., energy) for organisms. Because this is essentially a
definition, rather than a concept, sharing this information directly with students would be appropriate. Following up with the student about how sleep
is related to energy can also be directed to provoke thoughts that lead to
food as the actual energy source: What happens during sleep that gives
your body more energy? Is sleeping like recharging a battery? What source
is used (instead of electricity from an outlet) for recharging?
Before trying to move this student’s thinking about food storage forward,
the teacher should probably try to get a better understanding of what the
student is actually thinking. Additional probes could include the following:
Think about the path of food after it is eaten. Does all of the food in an
animal end up in the same place? Does all of the food leave the animal’s
body? What happens to the food that stays inside the animal?
Depending on the student’s response, it may be important to discuss the
various pathways that food can take. Food can be used immediately as fuel
or building material. But if not used immediately, food can also be stored for
later use or, in animals only, eliminated from the body as waste.
It may help to discuss real-world examples that suggest organisms use
released energy from stored food. For instance, animals can function for a
while without ingesting food, and plants will function for a while without light.
activities and questions that draw out student thinking.
Even more difficult is the task of attending to student
ideas that surface. The best approach for addressing
those incorrect or incomplete ideas is not always clear, and
research in this area is limited. It does seem to be clear,
however, that teachers, in a sensitive way, need to find
situations that engage students in cognitive conflict and
then discuss the conflicting viewpoints (Bransford, Brown,
and Cocking 2000). Because the nature of student ideas
in any specific case is largely determined by the content
itself, it is not clear that generally applicable guidelines
describing how to engage students in cognitive conflict
would be helpful. Instead, Figure 4 offers three different
examples of how a teacher might go about eliciting and
analyzing particular students’ ideas about the flow of
matter and energy in living systems, as well as possible
strategies for moving students forward in their thinking
about those ideas. (For similar prompts in other areas of
science, check out NSTA’s Uncovering Student Ideas in
Science, volumes 1–4, available at www.
nsta.org/store.)
Beyond eliciting students’ initial
ideas, it is also important for teachers
to use formative assessment strategies to monitor the development of
students’ ideas throughout a unit and
make instructional adjustments when
required (Boston 2002; Shepard 2000).
For example, having students respond
to prompts such as “Today I learned
____, but I’m not clear on ____” provides
opportunities for teachers to quickly assess student thinking. One suggestion
for this topic would be to have students
create a diagram (e.g., concept map,
Venn diagram, or cartoon) at the beginning of the unit that depicts their current
thinking of how plants and animals get
and use food, using guiding questions
to help them make their own thinking
explicit:
a. What is food? Why do organisms
need it?
b. From where does food come?
c. How is food used for growth?
d. How is food used for energy?
Periodic reflections on students’ learning throughout the unit would likely
signal a need to modify their diagrams
or create new ones. A student’s graphic representation of these science ideas during the unit
may be similar to the diagram shown in Figure 5. By the
end of the unit, students would have a visual representation of the entire learning goal, portraying an understanding of each of the component ideas and the connections among them.
Finally, it is important that teachers be aware of how
language can influence students’ thinking (Michael
et al. 1999). Teachers have the difficult task of using
words and language that students understand, although
such language may actually reinforce the wrong ideas
(Veiga, Cost Pereira, and Maskill 1989). For example,
teachers need to be attuned to their wording when talking about the use of food for energy because students
often incorrectly think that food is turned into energy,
missing the idea that the breakdown of sugars (i.e.,
food) into simpler substances (e.g., carbon dioxide and
water) is accompanied by the release of energy; sugars
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investigating students’ ideas About the flow of matter and energy
FIGURE 6
Using purposeful language to prevent the formation or reinforcement of misconceptions
Frequently used phrase
Associated inaccurate
interpretation
Food is used for energy.
Food is turned into energy.
The breakdown of food releases energy.
Plants turn sunlight into sugars.
Sunlight is an ingredient in photosynthesis, and light energy is
contained in plant sugars.
Plants use light energy in the formation of sugars (from carbon dioxide
and water).
Plants make food.
Plants make food for animals.
Plants make their own food.
do not become energy. Also, it is important not to convey
inaccurately the idea that sunlight is an ingredient in
photosynthesis. Students need to understand that plants
use light energy to chemically combine carbon dioxide
and water; light energy is not contained in the resulting
sugars but is instead transformed into chemical energy
stored in these sugars. Similarly, care should be taken
when referring to plants “making food.” A common misconception is that plants make food for animals rather
than using the food they make for their own growth and
energy. Associations among frequently used phrases,
inaccurate interpretations, and alternative wording that
produce greater clarity are shown in Figure 6. Using
purposeful language is one way to prevent the formation
or reinforcement of misconceptions.
Conclusion
As middle school teachers prepare for and teach units
on the flow of matter and energy in living systems, it is
important that they attend to students’ thinking about
the way the world works. Undoubtedly, students will
come to class with a variety of ideas—some correct,
some incorrect, and some partially correct—about
the topic. Paying attention to students’ ideas and
monitoring their development throughout the unit
will improve student learning, a goal of all teachers. n
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Alternative wording
SCIENCE SCOPE
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Melanie Taylor and Kimberley Cohen are consultants,
R. Keith Esch ([email protected]) is a
research associate, and P. Sean Smith is a senior
research associate for Horizon Research Inc., located
in Chapel Hill, North Carolina.