Cycling of Matter
Matter and Energy
Cycling Matter
Part I: Water’s Trip Around the World
Transpiration
What is the Water Cycle?
Three of the key processes in the water cycle are
evaporation, condensation, and precipitation. In the water
cycle, water moves from the land to the air through the
process of evaporation. In order for water to change phase
from a liquid on the land to a gas in the atmosphere, heat
energy must be added to water. The Sun is the usual source
of heat in the water cycle. Another way to think about
evaporation is that it’s one of the processes that connects
the atmosphere to the living systems on Earth. Some of the
water that enters the atmosphere comes from plants through
a process known as transpiration.
Earth’s water is not evenly distributed throughout
the water cycle. Instead there are parts of the cycle
that serve as large water reservoirs, locations
where water is stored for long periods of time
before transferring to other locations. By far, the
largest reservoir in the water cycle is the ocean
which contains about 97% of all Earth’s water.
Other reservoirs are the frozen water in glaciers
and the groundwater found in Earth’s crustal rocks.
Water molecules can be stored for millions of years
in one of these reservoirs before they reenter the
water cycle.
Start a “Cycles Travel Journal” by reading the
postcard that your teacher gives you from Water. In
the postcard, Water will tell you about its journey
around the world. Then tape the postcard in the
space provided and answer the questions in your
Student Journal.
Tape the postcard in the space provided and answer the questions in your Student Journal.
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Cycling of Matter
Matter and Energy
Part II: Nitrogen’s Trip Around the World
You may find it interesting that most of Earth’s atmosphere
is actually composed of nitrogen. In fact, over 78% of our
atmosphere is made of nitrogen! Is there evidence that
nitrogen cycles to other parts of the Earth? Nitrogen is
required by all organisms for the basic processes of life to
make proteins, to grow, and to reproduce, but most
organisms cannot use the nitrogen directly from the air.
One family of plants, called legumes, are especially
important for taking nitrogen from the atmosphere and
making it available to all living organisms. Legumes
connect the atmospheric nitrogen to the nitrogen chemicals
that plants and animals can use. Peas, beans, lentils,
peanuts, alfalfa, soybeans, and clover are all classified as
legumes.
A form of nitrogen called nitrates is used by plants and
animals. Nitrates are returned to the soil in the form of
animal feces (waste) and decaying plant and animal
matter. The decaying process is the action of bacteria and
fungi that decompose the plant and animal waste, forming
a nitrogen-rich layer of matter in the soil called humus.
Over time other bacteria continue to break down the
nitrogen-rich matter into simpler forms, thus releasing
nitrogen back into the atmosphere, thereby completing
the cycle. One place that this process can be observed
is in a compost bin.
Continue to the next page.
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Cycling of Matter
Matter and Energy
Part II: Nitrogen’s Trip Around the World, continued
1.  Continue your “Cycles Travel Journal” with the adventures of nitrogen.
2.  This time you write the postcard as if you where the element nitrogen. Refer to the postcard
that your teacher gave you from Water to use as a postcard example.
3.  Since you are “Nitrogen,” use the Nitrogen Cycle Diagram to help describe your travels around
the world. Nitrogen’s journey will be very different from Water’s journey.
4.  Your teacher will give you an index card that you will use to write your postcard.
5.  Be creative about your travels as “Nitrogen” yet accurate with regard to how and where you
traveled. Your postcard must include at least five separate places that you visited in your
journey.
6.  Exchange your postcard with your partner. Discuss any differences in your journeys.
7.  Then tape your postcard in place and answer the questions about the nitrogen cycle in your
Student Journal.
Nitrogen Cycle
Diagram
Tape the postcard in the space provided and answer the questions in your Student Journal.
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Cycling of Matter
Matter and Energy
Part III: Carbon’s Trip Around the World
The element carbon is one of the most important elements on our planet. All living organisms
contain carbon, making it an essential component of all life on planet Earth. In fact, the element
carbon makes up close to half of the biomass of all living things! Biomass is a source of energy
composed of plant materials or animal waste.
So where does all of this carbon come from, and how does it move around? Carbon is freely
cycled between the living systems and the atmosphere. Carbon is found in our atmosphere in
forms such as carbon dioxide. Carbon is found in rocks and volcanic materials. Carbon is found in
all living organisms. When organisms die, it is returned to the soil through the process of decay.
Carbon is also found in fossil fuels such as natural gas and oil, and when these fuels are burned,
carbon is returned to the atmosphere.
Carbon’s Trip Around the World
Continue to the next page.
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Cycling of Matter
Matter and Energy
Part III: Carbon’s Trip Around the World, continued
1.  Continue your “Cycles Travel Journal” with the adventures of Carbon.
2.  Complete another postcard, this time as if you were “Carbon.”
3.  Be creative about your travels as “Carbon” yet accurate with regard to how and where you
traveled. Your postcard must include at least five separate places that you visited in your
journey.
4.  Exchange your postcard with your partner. Discuss any differences in your journeys.
5.  Then tape your postcard in place and answer the questions about the carbon cycle in your
Student Journal.
The Carbon Cycle
Tape the postcard in the space provided and answer the questions in your Student Journal.
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Cycling of Matter
Matter and Energy
Part IV: The Compost Bin: Linking the Nitrogen Cycle, Water Cycle, and
Carbon Cycle Together
In order to understand how water, carbon, and nitrogen all play a major role in some important
biological processes, such as decomposition, you need to focus on the bacteria. Composting is an
example of a process that relies on bacteria as decomposers. Although composting sets up
conditions similar to those in humus-rich soils found in forest floors, composting is a process that
we use to speed up the natural rate of decomposition of matter. Bacteria play a major role in the
decomposition process. Therefore, it is not an exaggeration to say that whatever is good for
bacteria is good for the compost bin!
How to Nurture Your Class Compost Columns
Bacteria, like all other organisms need food, water, and shelter. Too much or too little of these three
variables will affect the bacterial activity in the soil or in the compost bin. To provide the best
environment for bacteria to grow and reproduce, it is important to control the moisture content,
temperature, oxygen, carbon, and nitrogen in the compost.
Water: Bacteria need water to survive so if the
compost is too dry, bacterial activity will be very
slow. On the opposite end of the scale, too much
water will limit the amount of oxygen moving
through the small pore spaces of the soil.
Oxygen: Many types of bacteria need oxygen.
If there is not enough oxygen present (or too much water),
the only types of bacteria that can grow are the types
that produce unpleasant odors, making the compost bin offensive.
Water Nitrogen Temperature: The best composting temperatures are in the range between 49° C and 66° C (120°
F and 150° F). This warm environment stimulates rapid growth of heat-loving bacteria that promote
decomposition of matter.
Please continue to the next page.
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Cycling of Matter
Matter and Energy
Part IV: The Compost Bin: Linking the Nitrogen Cycle, Water Cycle, and
Carbon Cycle Together, continued
Nutrition: Like all living things, bacteria need carbon and nitrogen to grow and reproduce. Most
bacteria need a food source that contains about 25 times as much carbon as nitrogen. If there is
too much nitrogen compared to the amount of carbon, the extra nitrogen will be released into the
air in the form of ammonia.
Worms: Worms are important too! Worms are detritivores, which means they
consume decomposing material for energy. Worms will produce carbon
dioxide when they breathe (respiration). They also rely on the calcium and
carbon found in rocks and egg shells. They release nitrogen into the
ground through their feces.
Use your knowledge of the water cycle, the nitrogen cycle, and the carbon cycle and your
observations of the compost column created by your class to answer the questions in your Student
Journal.
Answer the Part IV questions in your Student Journal.
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