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A water cycle of many paths
by Matthew Vick
T
here is much more to learning the water cycle
than memorizing the definitions of evaporation,
condensation, and precipitation. The following
activity allows students to explore the complexity
of the water cycle, create their own model of it, and
connect it to the processes that drive it. This activity works best after students have reviewed the basic
water cycle and how states of matter change. They
should understand how the Sun provides energy to
change states of matter and how gravity pulls objects,
including water, toward the center of the Earth.
This activity addresses the Next Generation Science Standard (NGSS) MS-ESS2-4, which requires
students to create models of the hydrologic cycle
and identify water in different states of matter as it
moves through various pathways driven by the Sun
and gravity (NGSS Lead States 2013). Additionally,
this activity engages students in the science and engineering practice Developing and Using Models as
they describe phenomena and unobservable mechanisms. This activity also addresses disciplinary core
idea ESS2.C: The Roles of Water in Earth’s Surface
Processes: “Water continually cycles among land,
ocean, and atmosphere via transpiration, evaporation,
condensation and crystallization, and precipitation,
as well as downhill flows on land” (NGSS Lead States
2013). The crosscutting concept Energy and Matter:
Flows, cycles, and conservation is also linked to this
activity (see standards sidebar on p. 63). This complex water-cycle activity follows a 5E/7E format (Bybee 1997; Eisenkraft 2003).
This game and reflection have some similarities with
the FOSS water-cycle activity used in the FOSS Weather
and Water Middle School Course and the FOSS Weather
on Earth Grade 5 Third Edition Module, which FOSS in
turn adapted from an activity created by Patty W. Watts
and Eric A. Pani (1999). The activity described in this
paper was developed independently and does have differences (as confirmed by FOSS staff).
Elicit/Engage
Begin by asking students to draw a diagram of the water
cycle. Most draw a simple diagram with three or four
steps, such as a lake with an arrow pointing upward
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toward a cloud and rain falling from the cloud back to
Earth. Typically, they label the arrow as evaporation, the
cloud as condensation, and the rain as precipitation. Occasionally, they include water seeping into the ground
(and possibly include groundwater). When asked what
the state of matter of the water is in while in the cloud,
students most often describe it as being a “gas” or “water
vapor,” a common misconception identified by Keeley,
Eberle, and Dorsey (2008, p. 159).
Ask students to share the parts of their diagrams
and compare their diagrams to each other’s. These initial diagrams often look similar to the public-domain
graphic shown in Figure 1, which depicts a single cycle
involving only evaporation, condensation, and precipitation. You can now challenge this conception.
Explore
In this activity, students travel through the “life” of a
drop of water in a complex manner that shows them
water molecules do not simply flow through a single,
predictable cycle of evaporation, condensation, and
precipitation. While any number of stations can be
created by the teacher, I chose to set up 11 stations
around the classroom. Each station represents a different location where water exists and is symbolized by a
different color: an ocean (dark blue), the air (yellow),
a cloud (white), a lake (light blue), an animal (orange),
the ground (green), groundwater (brown), human use
(black), a factory (gray), the human body (red), and
a plant (violet). I chose stations that helped students
realize how water is used by a variety of organisms
(animals, plants, and humans). A summary of the stations and station directions, which are written on cards
placed at each, can be found in Figure 2. Students keep
track of the stations through which they progress by
either coloring a strip of paper or adding beads to a
string, using colors that correspond to the stations they
visit. The beads are slightly more efficient in terms of
time, but these must be bought, as opposed to crayons
and paper, which are readily available in classrooms.
You can re-collect and re-sort the beads to use in the
future, if desired. If you are using beads, put about 20
of the corresponding color in a cup at each station. If
you are using crayons, place a few of the correspond-
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ing color at each station. (Safety note: If using beads,
be sure to remind students that they are a choking hazard and should not be played with.)
Before starting, students are given a die to carry
with them throughout the activity. If using colored
beads, also give students a piece of string about 30
cm long. Otherwise, give each student a strip of paper
about 30 cm long by about 5 cm wide. Each student is
then randomly assigned a station at which to start. I
usually have students move to one of their choice, with
a limit of no more than three people at a station. Students place a bead the same color as their station on
the string or color about 2.5 cm of the strip of paper the
same color as the station.
Students are now ready to independently begin the
activity. They roll their die and then follow the directions at their station that correspond to the die number rolled. For example, if a student who starts at the
Orange Station (Animal) rolls a 1 or 2, the animal exhales the water into the air as vapor, and the student
proceeds to the Yellow Station (Air) and adds a yellow
bead to their string. The student would then roll the die
at the Yellow Station and continue in a similar manner.
If the student rolls a 3 or 4 at the Orange Station, the
water remains in the animal’s body and another orange
bead is added to the string. Finally, if the student rolls
a 5 or 6 at the Orange Station, the water is excreted
by the animal and the student proceeds to the Green
Station (Ground), where a green bead should be put
on the string. The student would then roll the die and
follow the directions at the Green Station in the same
manner. The beads accumulate as students move from
station to station, showing the “path” that they took.
It may take several rolls before the students leave
their present stations, as many of the stations’ directions have options to remain there if certain numbers
are rolled. Student should continue rolling and moving
from station to station until they find their way back
to their original station. At that point, they either tape
the strip of paper together or tie off the string to make
bracelets representing a water cycle. Usually, 5–10
minutes is long enough for most students to return to
their point of origin. If students finish quickly (due to
the random chance of their dice rolls), they can perform a second cycle, which will undoubtedly differ
from the first. If students do not return to their point of
origin by the end of class, they can tie off their string to
create a strand, which will indicate that their cycle has
yet to come to an end. Both short and long cycles will
be examined during the discussion phase.
FIGURE 1
Simple water cycle similar to the
drawings of many students
HTTP://COMMONS.WIKIMEDIA.ORG/WIKI/FILE:SIMPLE_WATER_CYCLE.JPG
The teacher should make the following classroom
management considerations when organizing this activity. First, clearly model what to do at a station (take
a bead or color the paper, then roll the die, then follow the directions about which station to go to next).
Second, remind students about the appropriate volume
of voices expected during the activity. Third, move
around the room during the activity to make sure students are on task. They may get frustrated if they get
“stuck” at one station due to their die rolls, but let them
know that this is modelling what really happens in the
water cycle.
Explain
• After the Explore Phase, I ask students to answer
the following questions in groups of four to guide
their thinking: Compare your string/paper to
those of the other people in your group. Do you
have the same number of beads/markings? Are
they in the same order? What does that mean?
• Did anyone get stuck at one of the stations (does
anyone have many of the same-color beads/
markings in a row)? For how long? What does
that mean in real life?
• How does this activity challenge the water cycles
you all drew earlier?
• Which of the station changes in water’s state of
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matter does the Sun “drive” in your cycles? [Give
students a handout with a list of the stations to
refer to.]
• Which of the station changes does gravity “drive”
in your cycles?
Students usually recognize that there are many pos-
FIGURE 2
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sible water cycles that a drop of water can follow. They
also come to realize that the traditional, three-step
water cycle is limited compared to the many different
factors that actually affect the cycle. Some students
point out that there are smaller cycles within an overall
cycle. Often, they remark that they have never thought
about how complex the water cycle is.
Directions for the stations
Dark Blue Station: Ocean
1,2,3: You evaporate and go into the air. (Go to Yellow Station.)
4,5,6: You remain a part of the ocean.
Yellow Station: The air
1,2,3: You condense (turn into liquid) and become part of a cloud. (Go to White
Station.)
4,5,6: You remain water vapor in the air.
White Station: Cloud
1,2: You remain in the cloud.
3,4: You fall as rain onto the ground. (Go to Green Station.)
5: You fall as rain into a lake. (Go to Light Blue Station.)
6: You fall as rain into the ocean. (Go to Dark Blue Station.)
Light Blue Station: Lake
1,2: You evaporate and become part of the air. (Go to Yellow Station.)
3,4: An animal drinks you. (Go to Orange Station.)
5,6: Humans process you into drinking water. (Go to Black Station.)
Orange Station: Animal
1,2: The animal exhales you into the air as vapor. (Go to Yellow Station.)
3,4: You remain in the animal’s body.
5,6: You are excreted by the animal. (Go to Green Station.)
Green Station: Ground
1: You soak into the ground and become groundwater. (Go to Brown Station.)
2: You run off into a nearby lake. (Go to Light Blue Station.)
3,4: You soak into the ground and are pulled into a plant by its roots. (Go to Violet
Station.)
5,6: You evaporate back into the air. (Go to Yellow Station.)
Brown Station: Groundwater
1,2,3: You remain underground.
4,5,6: Humans pump you up. (Go to Black Station.)
Black Station: Human use
1,2,3: You are drunk by humans. (Go to Red Station.)
4,5,6: You are used in a factory to cool machinery. (Go to Gray Station.)
Gray Station: Factory
1,2,3: You continue to cycle around the pipes in a factory.
4,5,6: You are released into the air as water vapor (gas) and steam (liquid). (Go to
Yellow Station.)
Red Station: Human body
1,2: You are exhaled into the air. (Go to Yellow Station.)
3,4: You remain in a human’s body.
5: You are excreted. You go into a lake. (Go to Light Blue Station.)
6: You are excreted. You go into groundwater. (Go to Brown Station.)
Violet Station: Plant
1,2: You remain a part of the plant.
3: An animal eats part of the plant. (Go to Orange Station.)
4: A human eats part of the plant. (Go to Red Station.)
5,6: You are evaporated through the plant’s leaves. (Go to Yellow Station.)
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Elaborate/Evaluate
Now ask students to draw a revised water-cycle diagram based on the activity. While each student’s activity path, as recorded by the beads or markings, can be
a starting point, students should be directed to draw a
water cycle that involves all 11 stations. They should
be incorporating information about the path they took
through the station as well as those of their peers when
constructing the diagram. In other words, students
should include examples of the stations they visited
(such as a factory using water). Additionally, students
are asked to identify the processes involved and whether each stage of the water cycle is driven by the Sun or
by gravity. They should be able to draw on background
knowledge about phase changes. Guiding questions
to ask students include: “Is the Sun involved when water freezes? When it evaporates? When it condenses?”
FIGURE 3
Student diagrams should look more like a web than a
simple circle. You can also ask students: “Where in the
water cycle did transpiration, evaporation, condensation and crystallization, and precipitation occur?” Have
students label these processes on their water cycle
as called for by NGSS ESS2-4. Depending on their
background knowledge, you may have to review the
definitions of these terms. Some of the stations will
be difficult for students to label (such as what draws
groundwater into roots or how water is cycled around
a factory for cooling).
Students should then label the driving forces for
each of the transitions. This can be done on their water-cycle diagram or in a separate table. Students can
use informational texts or online resources to find
ways to describe what is happening. Textbooks usually have sufficient definitions of transpiration, evapo-
Processes and driving forces for water-cycle stages
Starting station
Ending station
Process
Driving force
Ocean
Air
Evaporation
Sun
Air
Cloud
Condensation/crystallization
Temperature/altitude
Cloud
Rain
Precipitation
Gravity
Lake
Air
Evaporation
Sun
Lake
Animal/human
Drinking
Physiological forces
Animal
Air
Respiration/exhaling
Physiological forces
Animal
Ground
Excretion
Physiological forces/gravity
Ground
Groundwater
Percolation/filtering
Gravity
Ground
Plant
Capillary action/transpiration
Water cohesion/osmotic pressure
Ground
Air
Evaporation
Sun
Ground
Lake
Runoff
Gravity
Groundwater
Humans
Pumping
Displacement or gravity
Humans
Humans
Cooling factory equipment
Displacement or gravity
Human
Air
Respiration/exhaling
Physiological forces
Human
Lake
Excretion
Physiological forces
Human
Groundwater
Excretion
Physiological forces/gravity
Plant
Animal/human
Digestion
Physiological forces
Plant
Air
Transpiration
Sun
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ration, condensation, and precipitation for students to
use. The American Chemical Society’s online middle
school resources also have a good interactive site for
phase changes (see Resources). Figure 3 summarizes
the processes and driving forces for the changes in water’s state of matter during the activity. (The rubric for
the student-constructed water cycle is available with
the online version this article, located at www.nsta.org/
middleschool/connections.aspx.)
Finally, students should write a brief reflection on
how their model of the water cycle shows its complexity. A good prompt is: “How is this model of the water cycle more complex than the one you previously
learned about?” Follow up with questions that relate to
the NGSS science and engineering practice Developing and Using Models, such as: “How does this model
accurately describe the real world? What are its limitations?” The crosscutting concept Energy and Matter
relating to natural systems is addressed when students
can describe the processes that drive the changes in
water’s state of matter. Ask students: “How do the Sun
and gravity drive the changes in the state of matter of
water as it travels through its cycle?” Additional assessment tools for water-cycle content knowledge can be
found online. The Environmental Protection Association (EPA) provides a free, 25-question quiz with immediate feedback about the water cycle and water usage
(see Resources).
Students can also construct an argument to answer
the questions: “How can humans alter part of the water
cycle? What effect will this have?” Students need to defend their response with research from informational
texts or websites. For example, you can ask them how
the water cycle modeled in the game would be impacted if humans decreased the amount of water percolating into the soil by paving land for streets and parking
lots. Other questions requiring higher-order thinking
include:
• How can humans impact the driving forces for
parts of the water cycle?
• How would a hurricane impact the water cycle?
• How do severe thunderstorms affect parts of the
water cycle?
Extension
Students are now ready to write their own questions
about the water cycle based on the activity and then conduct research to answer their question using books and
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media resources. For example, after drawing the water
cycle and discussing it, students have asked, “Is the water cycle the same everywhere on Earth?” and “Does
anything change the water cycle?” Students should seek
websites and books to answer their questions. Questions can also be posed that connect the water cycle to
other science topics. Such questions include:
• How do ice ages affect the water cycle?
• How does the water cycle affect water salinity in
different regions of the Earth?
• How is the water cycle used to preserve food?
• How does the water cycle cleanse water?
• How is pollution affected by the water cycle?
• How do specific animals (such as beavers) affect
the water cycle?
The Drop in My Drink: The Story of Water on Our
Planet (Hooper 1998) from the National Science Teachers Association’s Outstanding Science Trade Books for
Students K–12 (see Resources) is a great picture book
that describes the history of water on Earth, beginning with the formation of the planet. Another book
from this list, Our World of Water: Children and Water
Around the World (Hollyer 2008), is also a good starting point to link the activity described in this article
to other subjects. It can help students to analyze how
various cultures use water and how its scarcity affects
them. Students can link the concepts from these texts
to their constructed water cycles by determining the
parts of the water cycle that are affected by geography
or human activity.
More than vocabulary
This activity should not be seen as an end unto itself.
The most important part of the lesson is in the discussion after the activity, in which students process the
way their traditional, simplistic view of the water cycle
has been challenged. From there, they create their
own visual model to demonstrate their understanding
of the multiple pathways present in the water cycle,
the processes involved, and the forces that drive
them. Like all models, the water cycle is never a complete replica of nature; it can be modeled with different levels of complexity that serve as a “good enough
model” for the question being asked (Gustafson and
Mahafy 2011). ■
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References
Bybee, R.W. 1997. Achieving scientific literacy: From
purposes to practices. Portsmouth, NH: Heinemann.
Eisenkraft, A. 2003. Expanding the 5E model: A proposed
7E model emphasizes “transfer of learning” and the
importance of eliciting prior knowledge. The Science
Teacher 70 (6): 56–59.
Gustafson, B., and P. Mahaffy. 2011. The concept of a
model: Ways to teach students the meaning behind
models and not just what they represent. Science and
Children 49 (1): 73–77.
Hollyer, B. 2008. Our world of water: Children and water
around the world. New York: Henry Holt Books for Young
Readers.
Hooper, M. 1998. The drop in my drink: The story of water
on our planet. New York: Viking.
Keeley, P., F. Eberle, and C. Dorsey. 2008. Uncovering
student ideas in science: Another 25 formative
assessment probes. Arlington, VA: NSTA Press.
NGSS Lead States. 2013. Next Generation Science
Standards: For states, by states. Washington, DC:
National Academies Press. www.nextgenscience.org/
next-generation-science-standards.
Watts, P.W., and E.A. Pani. 1999. Water-cycle game:
Learning about the hydrologic cycle and global
climate change: A demonstration. Fifth International
Conference on School and Popular Meteorological and
Oceanographic Education: Weather, Ocean, Climate.
Australian Meteorological and Oceanographic Society
5–9: 206–209.
Resources
EPA water-cycle quiz—www.epa.gov/ogwdw/kids/flash/
flash_qagame.html
Outstanding Science Trade Books for Students K–12—
www.nsta.org/publications/ostb
Phase-change resources—www.middleschoolchemistry.
com/multimedia/chapter2/lesson3
Matthew Vick ([email protected]) is an assistant
professor at the University of Wisconsin–Whitewater in Whitewater, Wisconsin.
Connecting to the Next Generation Science Standards (NGSS Lead States 2013)
Standard
MS-ESS2: Earth’s Systems www.nextgenscience.org/msess2-earth-systems
Performance Expectation: The materials/lessons/activities outlined in this article are just one step toward reaching
the Perfomance Expectation listed below.
MS-ESS2-4. Develop a model to describe the cycling of water through Earth’s systems driven by energy from the
Sun and the force of gravity.
Matching student task or question taken directly
from the activity
Dimension
Name or NGSS code/citation
Science and
Engineering Practice
Developing and Using Models
How does this model accurately describe the real
world? What are its limitations?
Disciplinary Core Idea
ESS2.C: The Roles of Water in
Earth’s Surface Processes
Where in the water cycle did transpiration,
evaporation, condensation and crystallization, and
precipitation occur?
• Water continually cycles among
land, ocean, and atmosphere
via transpiration, evaporation,
condenstation and crystallization, adn precipitation as well as
downhill flows on land.
Is each stage of the water cycle is driven by the Sun
or by gravity?
• Global movements of water and
its changes in form are propelled
by sunlight and gravity.
Crosscutting Concept
Energy and Matter
How do the Sun and gravity drive the changes in the
state of matter of water as it travels through its cycle?
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