SCIENCE SAMPLER
The Element Walk
by Dennis Smithenry
When teaching middle school students about the periodic table of elements (see NSES Physical Content Standard B, NRC 1996), we often find ourselves saying, “Everything around us is composed of elements.” Yet, what
does this statement really mean for our students? Do they
truly understand that every object around them is made
up of a collection of one or more types of atoms (i.e., elements)? And do they know which elements are in which
objects? A decade ago, I sought answers to these types
of questions by experimenting in my classroom. I placed
a group of 11 objects in front of my students, gave them
a periodic table, and asked them to identify the main elements contained in each. The group of objects consisted
of the following: a rock, a plastic bottle, a piece of paper,
a soda can, a staple, an ice cube, a pile of salt, a pile of
sugar, a plant, our pet hamster, and a human (me!). The
results were surprising—students could only correctly
identify the main elements in less than three of these
objects. Students’ lack of practical knowledge indicated
to me that their classroom learning about the chemical
elements was disconnected from their application of that
learning in everyday experiences.
So how can we get our students to situate their learning
of the chemical elements within the context of the physical
world around them? How can we get them to connect the
periodic table of elements on the classroom wall to their
own lives? How can we help our students learn how to
answer this basic question: What are the main elements
in _____? I address these questions by presenting a classroom lesson that I call “The Element Walk.” This lesson,
which I have now enacted many times over, is effective
at teaching students the elements that exist in common
substances encountered every day. Students walk away
from the lesson with a set of general rules that help them
to easily identify the elements around them. They also end
up with a greater appreciation of the elemental compositions of living, once-living, and nonliving objects, and the
connections among the three categories. At the end of
the lesson, I have found that I can point to pretty much
anything…and students can give me a correct answer
about 90% of the time. Not bad for one lesson!
Preparing students
At the beginning of the lesson, I prepare students for the
upcoming walk by presenting the whole class with eight
different objects (e.g., an ice cube, a plant, a dime, a plastic
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bottle, a pile of sand, a wedding ring, a piece of paper, a
rubber band, etc.) I then review the ideas that all of these
objects are made of atoms, that there are about 100 different types of atoms, and these types of atoms (elements)
can be found on the periodic table. While handing out a
periodic table to each student in the class, I ask the class
to quietly think for several minutes about the following
question, which serves as the lesson’s learning goal: What
main elements are found in each of the eight objects? After
recording a few answers, several students typically raise a
hand to indicate that they are uncertain about which elements exist in some of the objects. I answer loudly enough
for the whole class to hear: “Don’t worry; it is okay to
make a guess now. You will be much more certain about
your answers at the end of this lesson!”
After they reflect and record answers in their journals,
I ask students to raise their hand if they think they know
which elements are contained within the ice cube. Usually
at least half of the students raise their hand. I call on one
student who, based on previous experiences, typically
gives the confident answers of either “hydrogen and
oxygen” or “H2O.” I draw a table on the board with two
columns, record “ice cube” in the left column, and enter
“H” and “O” in the right column. I point out these elements on the periodic table and emphasize the symbols
of hydrogen and oxygen. My purpose for beginning with
the ice cube example is to make certain that my students
understand the question that I asked earlier (What main
elements are found in each of the eight objects?) and know
what an appropriate answer would look like. I also explain
that there are likely other elements in the water due to
impurities, but these make up only a small amount and
are not part of the main elements in the water.
After this initial example, I ask students to form
groups of four, share their ideas about which elements
are contained in the other seven objects, and complete a
group table. I also ask the groups to place a star in their
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observation/date tables by the objects about which they
are most certain. I stress that this assignment will not be
graded; I am simply curious to find out what they already
know. I give students about five minutes to complete this
activity. When they are finished, I put one big data table on
the chalkboard and ask each group to enter in its answers.
Typically, the elements listed for each object will vary
widely across the groups. Also, the elements listed for at
least half of the objects will be incorrect. Some groups
will be more confident about their answers than others. At
this point, students typically want me to tell them if their
answers are correct. I don’t; instead, I use their request
to transition into the next phase of the activity where I
provide the learning goal.
FIGURE 1
Table in progress during The
Element Walk
Presenting the learning goal
To motivate students, I present a clear learning goal. I
tell students that at the end of the lesson, they will be
able to easily identify the main elements that are contained in the eight objects in front of them. I also tell
students that they will be able to identify the main elements in practically any object that exists around them.
I tell them that we are going to take a walk outside and
use the world around us to develop a set of rules that will
enable us to accomplish the learning goal.
Before going for the walk, I provide structure to the
activity by outlining five parameters. First, I tell the
class that as soon as we exit the building, I will be roleplaying as an “elemental analyzer.” I tell them that when
FIGURE 2
Completed table after
The Element Walk
Object
Main elements in object
Object
Main elements in object
ice cube
H, O
ice cube
H, O
tree
C, H, O
tree
C, H, O
bicycle tire
C, H
bicycle frame
Fe, C, Ti
leaf
C, H, O
dirt
Si, O
grass
C, H, O
lamp post (steel)
Fe, C
plastic bottle
C, H
glass window
Si, O
soda can
Al
sidewalk
Si, O
paper
C, H, O
chewing gum
C, H, O
penny coin
Zn, Cu
nickel coin
Cu, Ni
sun
H, He
body of a car
Fe, C
cigarette butt (filter)
C, H
sand
Si, O
dime
Cu, Ni
silver earring
Ag, Cu
salt
Na, Cl
Total # of unique
elements found
15 out of 15
Total # of unique
elements found
3 out of 15
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a student points to an object, I will be able to analyze
the main elements that are found within the object and
report my findings. Second, I tell students that they must
guide me to a specific object and that I, as the elemental
analyzer, will only listen to one person at a time. Also,
the elemental analyzer will only function with the class
huddled around it in one group and quiet during its analysis. Once the analyzer has given its report, students are
to record the data in a table in their journal. Third, each
student will have the opportunity to point to at least one
object before any student can point to a second object.
Fourth, I show a map of the school and surrounding
area and identify the perimeter boundary of where we
can go on the walk. Lastly, I provide an end goal to the
activity; students must point to enough objects until the
total number of unique elements that they have found is
15 (see Figures 1 and 2).
Taking The Element Walk
When we get outside, I hang an “Elemental Analyzer”
sign on my neck and make a buzzing noise to indicate
that the analyzer is on and ready to begin its work. In
their excitement, my students usually forget most of
the rules. They begin talking all at once and pointing to
all sorts of things. When I stand motionless and do not
respond, they ask me why I won’t answer. Being prepared, I pull the list of five rules for The Element Walk
out of my pocket, hand it to one student, and point to
the direction at the top that says, “Read this out loud to
your classmates.” After this student reads the rules, the
class guides me to one object and has one student point
to it. When they all get quiet, I touch the object, close
my eyes, and say, “Analyzing object” in a robotic voice. I
then tell them the elements contained in the object. For
example, if a student points to a tree, I do my “analyzing
object” bit and say, “Carbon, hydrogen, and oxygen…
C, H, and O.” Or if a student points to a rock, I reply,
“Silicon and oxygen…Si and O.” Or if a student points
to a bicycle, I reply, “Which part?” If students points to
the tire, I say, “Carbon and hydrogen…C and H.” If a
student points to the frame, I say, “Iron, carbon, and titanium…Fe, C, and Ti.”
At this point, you may be wondering how it is that
I know the main elements that are contained in any
object to which they point. As you will see in the example data that students collect, there are patterns
(and thus rules) that I use to identify the elements.
There are times when these rules do not work, and,
frankly, I am uncertain about the elements that exist
in a particular object. In those few instances, I simply
say something like, “Insufficient data for analysis” and
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move away from the object. Students tend to find this
answer hilarious.
Some of the rules for identifying elements become
apparent to students during the walk. For example, after
about the sixth or seventh time that students point to some
type of living object and get the same answer, “Carbon,
hydrogen, and oxygen…C, H, and O,” the class groans.
Students show frustration because they need to find 15
new unique elements, and pointing to plants or animals
does not lead them closer to this goal. Students begin to
direct each other not to point to any living object because
they all contain C, H, and O. The same thing begins to
happen with plastics (all contain C and H) and rock-like
objects (all contain Si and O).
I have found that about 15 minutes into The Element
Walk, students usually get stuck at the 8 to 10 unique
elements, and get a little frustrated that ever ything
around them seems to contain the same few elements.
Eventually, a student thinks to point to a silver earring
or a gold bracelet or a coin. To the relief of my students,
these choices quickly add several more elements to the
tables in their journals: Ag, Au, Zn, Cu, and Ni. If this
does not complete the list, I start gulping air and begin
analyzing it, happy to report that there is N, O, and Ar.
This reporting usually completes students’ lists and we
are able return to the classroom. An example list of our
findings is presented in Figure 2.
Looking for patterns
When we get settled back in the classroom, I ask the class
to look for patterns in the data that were collected during the walk. I have students work in groups and write
down a list of rules that they think the elemental analyzer
used to identify the elements in the objects to which they
pointed. Once they have done so, we create a class list of
these rules on the board. Students typically begin with
FIGURE 3
Rules for identifying elements
in objects
Elemental Analyzer Rules
Living objects contain C, H, O
Once-living objects contain C, H, O
Rock-like things (dirt, glass, sand, concrete, etc.)
contain Si, O
Things made of steel contain Fe, C
Plastics mostly contain C, H
Most coins contain Cu, Ni (pennies—Cu, Zn)
Air contains N, O, Ar
Salt contains Na, Cl
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the rule that “living things contain carbon, hydrogen, and
oxygen.” An example list of rules is found in Figure 3.
Checking for understanding
At the end of the lesson, I ask students to return to the
initial learning goal, and we collectively use the newly
written rules to identify the elements in the eight objects
presented at the beginning of the lesson. Then, to check
that students understand how to apply these rules in a
new context, I tell them that I will be assessing their newfound skills with five new objects. I also inform them that
they will be assessed as a whole class. For this wholeclass assessment (Gallagher-Bolos and Smithenry 2008),
I tell students that I will be presenting them with one
of the five new objects for which they must identify the
main elements. I also tell them that for each object, they
will have up to five minutes to talk as a whole class to apply the rules and make their identification. At the end of
the five minutes (or when they indicate they are ready),
I will randomly select one student to provide an answer
(1 point) and to explain how he or she arrived at the answer (1 point). I indicate that every student in the class
will receive the same grade (out of two points) based on
this student’s response. Lastly, I tell them that this process will be repeated for each of the five objects, so the
class has the opportunity to earn a score up to 10 points.
After I take a few questions about how the whole-class
assessment will work, I place one of the five new objects
in front of the class. Upon doing so, students begin talking
immediately. For example, when I place a glass bottle on
the table, I typically hear several statements such as, “Glass
is made of sand,” “Sand comes from a rock,” “Rocks are
silicon and oxygen.” What’s great about this discussion is
that I get to hear students’ thinking. Of course, all students
can’t make a vocal contribution to this discussion. Yet, even
with only one-third of the class verbalizing its thoughts, the
nonvocal students can listen to the vocal students’ logic and
review the rules we developed earlier.
After a few minutes, a student tells me that the class
is ready (they rarely take the full five minutes). I draw
a student’s name. This student then tells me that the
main elements in the glass bottle are silicon and oxygen
because it is made from sand, which is a form of a rock.
The student finishes by saying, “And we know that rocks
contain silicon and oxygen.” In the several times that I
have conducted this lesson, there has only been one time
when the randomly chosen student could not successfully
identify the correct elements contained within a particular
object. I believe that this success rate speaks to both the
power of The Element Walk and the subsequent discussions during the whole-class assessment.
Taking it a few steps further
I try to take The Element Walk several steps further by
making connections between objects that contain similar
elements. For example, I ask students to tell me if they
know how plastic is made. If they don’t know, I inform
them that plastics are derived from petroleum, which is
a fossil fuel. I ask them to think about what fossil means.
They respond that fossils come from plants and animals.
Once this is said, it dawns on students that plastics ultimately come from ancient plants and animals. I drive
this point home by telling them it is quite possible that
some of the atoms in a plastic water bottle could have
existed in a dinosaur or a prehistoric plant. Students are
impressed with this bit of information and chatter about
it for the next few days! This connection is just one of
many that I use in my attempt to breathe life into the
periodic table of elements.
Building upon The Element Walk
By taking The Element Walk with your class, you can
teach your students how elements are a part of their daily lives. So now when you ask a question such as, “What
are the main elements in that wooden chair you are sitting in?” you won’t get blank stares. Instead, you will get
students who quickly respond, “Carbon, hydrogen, and
oxygen!” And now that your students have a situated understanding of the elements around them, you can move
them on to more challenging topics. For example, students can research how the three elements of carbon,
hydrogen, and oxygen combine and bond to form the
long cellulose molecules that allow the wooden chair to
be sat upon without buckling. Or, ask students to find
out how silicon and oxygen bond together to form a
glassy solid. Another idea is to have students explore the
way that carbon and hydrogen bond together to form
the polymers that make up a polyethylene bottle. These
are just a few ideas that can help you and your students
build upon The Element Walk.
References
Gallagher-Bolos, J.A., and D.W. Smithenry. 2008. Wholeclass inquiry assessments. The Science Teacher 75
(6): 39–44.
National Research Council (NRC). 1996. National science
education standards. Washington, DC. National Academies Press.
Dennis Smithenry ([email protected]) is an
assistant professor of education in the Department of
Education at Elmhurst College in Elmhurst, Illinois.
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