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All About Carbon Dioxide | A Student's Guide to Global Climate Change | US EPA

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All About Carbon Dioxide | A Student's Guide to Global Climate Change | US EPA

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Dinosaur Breath - Activity - www.TeachEngineering.org

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Dinosaur Breath - Activity - www.TeachEngineering.org

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Through discussion and hands-on experimentation, students learn about the geological (ancient) carbon cycle. They investigate the role of dinosaurs in the carbon cycle and the eventual storage of carbon in the form of chalk. Students discover how the carbon cycle has been occurring for millions of years and is necessary for life on Earth. Finally, they may extend their knowledge to the concept of global warming and how engineers are working to understand the carbon cycle and reduce harmful CO2 emissions.
This engineering curriculum meets Next Generation Science Standards (NGSS).

Pre-Req Knowledge

Students should be familiar with the main processes of the geological carbon cycle, including weathering, subduction, erosion and volcanic activity. It is also helpful if students have already been introduced to the concept of global warming and that human activity during the past 100 years has contributed to the increased emissions of carbon dioxide into the atmosphere.

Learning Objectives

After this activity, students should be able to:

Define carbon as a necessary component of the Earth that supports all forms of life.

Describe how it is possible that the carbon contained in chalk could possibly have originated from the respiration of a dinosaur living during the Jurassic Period.

Explain why engineers are working to understand and rebalance the carbon cycle.

Educational Standards
Suggest an alignment not listed above

Materials List

Each student needs:

Each group needs:

3-4 pieces of chalk (NOT dustless chalk)

rolling pin and hard surface to crush chalk

1 small sandwich bag in which to crush chalk

¼ cup vinegar (either red or white)

2 small beakers, graduated cylinders, or small glass jars

(optional) 1 small balloon

(optional) 1 tsp. baking soda (see Troubleshooting Tips)

For the entire class to share:

a few scales, to measure mass

Introduction/Motivation

Does anyone know what is contained in the piece of chalk I am holding in front of you? (Answer: Calcium carbonate.) Where would you guess this chalk is from (in terms of how it came to be "chalk")? Well, today we are going to find out! We are also going to learn why carbon is so important for life on Earth.

All living organisms, including plants and trees, fish in the ocean, and our own bodies, are made from the carbon atom. In fact, 18% of our bodies are made of carbon! Carbon atoms continually move through living organisms, the oceans, the atmosphere and the Earth's crust. This movement is known as the carbon cycle, which can take millions of years to complete.

Some carbon cycles, such as the carbon cycle that happens within our bodies when we eat, take less time to come full cycle. What did some of you eat today for breakfast? So, when you ate breakfast, you ingested carbon into your bodies in the form of carbohydrates and proteins. In your cells, oxygen combined with the food to give you energy for your day's activity. Carbon is a waste product of this process, and leaves your body when you exhale. Can anybody guess how carbon leaves our bodies when we exhale? I'll give you a hint - it's a gas, and plants and trees need it to produce energy. (Answer: Carbon dioxide, or CO ₂.)

Just as we are part of the carbon cycle, other animals are, too! Even dinosaurs that lived millions of years ago are part of the carbon cycle. Our experiment today will help us understand how the chalk that I am holding in front of you could contain carbon that was exhaled by a dinosaur that lived long ago. Can you imagine!?

First, can anyone tell me once more what chalk is made of? That's right - calcium carbonate. Can you guess where calcium carbonate/natural chalk comes from? A lot of natural chalk is mined from large rock formations such as the White Cliffs of Dover that form part of the British coastline. The Dover Cliffs are composed of calcium carbonate sediment. This sediment was created by the shells of ancient sea creatures that died and sank to the bottom of the ocean. These ancient sea creatures constructed their sturdy shells using some of the carbon that is found in the Earth's oceans. Oceans soak up a tremendous volume of carbon from the atmosphere. A long time ago, when dinosaurs walked the Earth, the Earth's oceans absorbed some of the carbon (as carbon dioxide) that was released when dinosaurs exhaled. So, it is very possible that the ancient carbon contained in a dinosaur's breath is here, in this piece of chalk today. Amazing!

You see, carbon atoms are never destroyed, they just move around and change form. Because the Earth can only tolerate so much carbon in one place at one time, it is important for scientists and engineers to understand how carbon cycles through the Earth. Today, many people are worried that human activities, particularly fossil fuel burning and deforestation are releasing unnatural amounts of carbon dioxide into the atmosphere, leading to global climate change. Humans burn fossil fuels such as coal, oil and natural gas, to produce energy to power our cars and light our houses and buildings. We practice harmful deforestation techniques when we clear cut forests for lumber. Deforestation emits carbon into the atmosphere as well.

Many engineers are working on creating beneficial technologies to reduce CO ₂ emissions. For example, environmental engineers are studying carbon sequestration, which is a term used to describe processes that remove carbon from the atmosphere. Mechanical and electrical engineers design buildings, homes, cars and appliances that use less energy. They are also engineering devices such as solar panels and wind turbines that generate electricity from renewable natural sources (the sun and the wind) and do not emit CO ₂ into the atmosphere.

Vocabulary/Definitions

atmosphere: The Earth's atmosphere is a layer of gases surrounding the planet and retained by gravity; contains roughly 78% nitrogen, 0.97% argon, 0.04% carbon dioxide; protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.

carbon cycle: The exchange of carbon between the land, the oceans, the atmosphere and the Earth's interior.

Carboniferous period: A major division of the geological time scale that extends from the end of the Devonian Period (360 million years ago) to the beginning of the Permian Period (299 million years ago). Carboniferous rocks in Europe and eastern North America consist largely of limestone, sandstone, shale and coal beds. The Carboniferous coal beds provided much of the fuel for power generation during the Industrial Revolution.

erosion: The displacement of soil, mud rock and other particles by wind, water, ice and downward slope movement caused by gravity. Erosion is different from weathering because it involves movement. Although erosion is a natural process, in many places it is increased by human land use.

fossil fuels: Fossil fuels such as coal, petroleum products and natural gas are sources of ancient biomass that were formed millions of years ago from the decay of plant and animal matter.

global warming: The observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades.

Jurassic period: The Jurassic period, also known as the Age of Dinosaurs, is a major unit of the geologic timescale that extends from the end of the Triassic Period (200 million years ago) to the beginning of the Cretaceous (145 million years ago).

photosynthesis: The process by which green plants create energy by absorbing solar energy and carbon dioxide from the atmosphere to produce carbohydrates (sugars). Plants "burn" these carbohydrates during respiration, which releases the energy contained in sugars to be used as fuel. Plants then release oxygen to the atmosphere, which is used for respiration by humans and other organisms.

respiration: The process by which an organism obtains energy through the reaction of oxygen with glucose to give water, carbon dioxide and ATP (energy).

subduction zone: An area on Earth where two tectonic plates meet and move towards one another, with one sliding underneath the other and moving down into the Earth's mantle. When an oceanic plate slides underneath a continental plate, this creates a zone with many volcanoes and earthquakes.

volcanic activity: Volcanic activity is caused by openings (or ruptures) in the Earth's surface or crust, which allows hot, molten rock, ash and gases to escape from deep below the surface. Volcanoes are usually found where two to three tectonic plates pull apart or come together. Volcanoes can also be caused by "hot spots" in the Earth's mantle. Volcanoes formed by hotspots are found elsewhere in the solar system, especially on rocky planets and moons.

weathering: The process of breaking down rocks, soils and their minerals through direct contact with atmospheric conditions such as heat, water, ice and pressure.

Procedure

Before the Activity (Teacher Preparation)

Gather materials and make copies of the Student Background Reading: Life of a Carbon Atom, and the Dinosaur Breath Worksheet.

Read "Life of a Carbon Atom" and answer the investigating questions at the end of the reading.

Prepare materials for the assessment activities, if desired.

With the Students

1. Show students several carbon-containing objects to grab their interest.

2. Review the activity tasks and learning objectives before starting the hands-on experiment. Write the objectives on the board or have students write them in their notebooks.

Table 1. Activity learning objectives and the activity tasks intended to achieve the objectives.

1. Have students read the attached background information, "Life of a Carbon Atom" and then work individually or in pairs to discuss the investigating questions at the end of the reading before beginning the hands-on experiment. Allow about 20 minutes.

2. After discussing the investigating questions in small groups or as a class, prepare students for the hands-on activity by explaining the activity set-up and procedure. The teacher may choose to demonstrate the activity for the students before they begin.

3. Have groups label their two beakers or small glass containers as: Container #1 and Container #2.

4. Next, have students seal their sticks of chalk into plastic bags. Using the rolling pin and a hard surface, crush the chalk into as fine a powder as possible.

5. Have students fill Container #1 with about four tablespoons of the crushed chalk OR the crushed chalk/baking soda mixture (see Troubleshooting Tips). Have them fill Container #2 with ¼ cup of vinegar.

Figure 1. Materials for the activity set-up.

1. Using the scale(*), have students measure the mass of Container #1 and Container #2 and record on their worksheets.

2. After students record the mass of the two containers, have them pour the vinegar onto the crushed chalk and observe the chemical reaction. (Note: chalk + vinegar = CO₂ [exhaled dinosaur breath] + water + calcium compound.)

3. Have students record the mass of the reaction products (water + calcium carbonate in Container #1). (Note: the mass of the reaction products should be less than the original combined mass of Container #1 and Container #2. This is because the chemical reaction between the calcium carbonate and the vinegar released some of the carbon that was stored in the chalk into the atmosphere.)

* Alternative Procedure: If scales are not available, the release of carbon from the crushed chalk can be observed by placing a balloon securely around the mouth of Container #1, very quickly after the vinegar has been added (see Figure 2).The balloon will fill with carbon dioxide; however, for the balloon to fill a noticeable amount, use a crushed chalk/baking soda mixture (see Troubleshooting Tips).

Figure 2. Alternate method to observe carbon release from chalk.

1. Have students describe the chemical reaction in qualitative terms - how did the reaction look, smell and sound? - on their worksheets.

2. Give students time to clean up their workspaces and finish their worksheets.

3. Conduct the creative writing post-activity assessment with the students or assign it as homework (see description in the Assessment section). Students need a sheet of paper and a writing utensil; markers, colored pencils and paint are optional.

Attachments

Safety Issues

Students should wear splash-proof goggles if conducting the activity using the Alternative Procedure.

Troubleshooting Tips

Because much of the chalk we use today is not natural chalk (pure calcium carbonate), the chemical reaction with chalk and vinegar is not as dramatic as it could be. One idea to evoke more of a "wow" reaction from the students is for the teacher to have the students crush the chalk and place it in a glass container, as described in the Procedures, and then add to the crushed chalk about one teaspoon of baking soda (sodium bicarbonate). The chemical reaction with the vinegar still produces CO ₂, but the reaction is more pronounced. Follow the rest of the procedures as written - that is, students should still record the mass of the chalk/baking soda mixture and determine how much carbon was released from the mixture as CO ₂. If conducting the alternative procedure, make sure students wear splash-proof goggles.

Assessment

Pre-Activity Assessment

Toss-A-Ball: Play a game to learn students' prior knowledge related to this activity. Divide the class into two teams and have one team start out with the ball. Ask one person from the team one of the questions from the list below. The teacher may want to ask additional questions to assess students' understanding of geological processes, global warming, carbon emissions into the atmosphere, and other real-world applications of the carbon cycle. If a team member answers the question correctly, his/her team receives one point and s/he has the opportunity to answer another question. If /when the team member answers incorrectly, s/he throws the ball to one of his/her teammates. If the teammate answers incorrectly, the ball is thrown to a person on the other team to give it a try.
Sample Questions 1. During what geological time period did dinosaurs live?
(Answer: Dinosaurs lived throughout the Mesozoic Era, which began 245 million years ago and lasted for 180 million years. It is sometimes called the Age of the Reptiles. The era is divided into three periods - the Triassic, Jurassic and Cretaceous.)
2. What element is the building block of life on Earth?
(Answer: Carbon)
3. What does the term "weathering" mean?
(Answer: Weathering is the process of breaking down rocks, soils and their minerals through direct contact with atmospheric conditions such as heat, water, ice and pressure.)
4. What is a subduction zone?
(Answer: A subduction zone is an area on Earth where two tectonic plates meet and move towards one another, with one sliding underneath the other and moving down into the Earth's mantle. When an oceanic plate slides underneath a continental plate, this creates a zone with many volcanoes and earthquakes.)
5. What is erosion?
(Answer: Erosion is the displacement of soil, mud rock and other particles by wind, water, ice and downward slope movement caused by gravity. Erosion is different from weathering because it involves movement.)
6. What is volcanic activity? What causes it?
(Answer: Volcanic activity is caused by openings (or ruptures) in the Earth's surface or crust, which allows hot, molten rock, ash and gases to escape from deep below the surface. Volcanoes are usually found where two to three tectonic plates pull apart or come together.)

Activity Embedded Assessment

Worksheet: Have students record measurements and follow along with the activity on their worksheet.s After students have finished their worksheets, have them compare answers with their peers.

Post-Activity Assessment

Worksheet Discussion: Discuss the results of the activity with students by reviewing the worksheet answers as a class. Did students find that adding vinegar to crushed chalk released some of the carbon contained in the chalk? Do they understand the chemical reaction? How is it possible that the carbon contained in the chalk is the same carbon that was exhaled by a dinosaur that lived long ago? Where is this carbon now? Why are engineers concerned about carbon in the atmosphere? What is global warming, and what can you do to help?

Creative Writing Practice: Have students write letters to a brontosaurus living the Jurassic Period from the perspective of a carbon molecule that was ingested by the brontosaurus in the form of a leafy fern and has recently found itself helping engineers to create technologies to help conserve energy. Ask students to explain the following:

Where is this carbon molecule today? For example, is the carbon molecule in an object, in the atmosphere, or in the process of moving from one place to another?

How did the carbon molecule arrive at its present state? Describe the events that occurred in the carbon molecule's life from the time of ingestion by the dinosaur to today. Was the carbon molecule previously in the atmosphere, as a CO ₂ molecule emitted from a respiring animal, a pile of decomposed wood or a power plant? Was the carbon molecule in a plant stalk or a human body?

What are the carbon molecule's plans for the future? Where is the best place for the carbon molecule to be if it does not want to contribute to global climate change? Have students imagine a technology that could be created by engineers to help reduce carbon emissions into the environment. How would this help reduce global warming?

Activity Extensions

Carbon Sleuth: Give each student a carbon-containing object or an image of that object and ask them to figure out how the carbon exists in the object and where the carbon came from. Suggested objects: chalk, leafy plants, sea shells, a piece of wood, humans and other animals, pencil lead, a diamond, coal, a balloon full of air, etc. Students may take this activity home to conduct independent research and/or use the school library or Internet, if available. See the References section for some appropriate student websites.

Activity Scaling

For more advanced students, have them draw two carbon cycles - the geological carbon cycle and the biological/physical carbon cycle. Ask them to explain the differences between the two cycles, how they are interconnected, and the human role in each cycle. Have them explain why engineers and scientists are working to understand and rebalance the carbon cycle.

References

Wilson, Jim. National Aeronautics and Space Administration. Accessed May 25, 2007 http://earthobservatory.nasa.gov/

U.S. Environmental Protection Agency, Kids Site, October 23, 2006. Accessed May 29, 2007. http://www.epa.gov/climatechange/kids/

University Center for Atmospheric Research, Global Climate Change. Accessed October 14, 2006. http://www.ucar.edu/learn/1_4_2_16t.htm

Other Related Information

This activity was selected to be part of the Climate Literacy & Energy Network (CLEAN) reviewed and annotated digital library collection. CLEAN, an NSF National Science Digital Library (NSDL) Pathway, seeks out exemplary digital resources that relate to key climate and energy concepts, are scientifically robust and current, and are easily accessible online. The focus is on strong learning activities, with solid pedagogical scaffolding for grades 6-16. This resource passed a rigorous peer-review process as part of being selected to be included in the collection in April 2011. For the complete review, see: http://cleanet.org/resources/41913.html .

Contributors Lauren Cooper; Malinda Schaefer Zarske; Janet Yowell

Copyright © 2007 by Regents of the University of Colorado

Supporting Program Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

Acknowledgements

The contents of this digital library curriculum were developed under grants from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and the National Science Foundation (GK-12 grant no. 0338326). However, these contents do not necessarily represent the policies of the Department of Education or the National Science Foundation, and you should not assume endorsement by the federal government.

Last modified: March 22, 2018

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Through discussion and hands-on experimentation, students learn about the geological (ancient) carbon cycle. They investigate the role of dinosaurs in the carbon cycle and the eventual storage of carbon in the form of chalk. Students discover how the carbon cycle has been occurring for millions of years and is necessary for life on Earth.

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Carbon Cycles - Lesson - www.TeachEngineering.org

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Carbon Cycles - Lesson - www.TeachEngineering.org

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Students are introduced to the concept of energy cycles by learning about the carbon cycle. They learn how carbon atoms travel through the geological (ancient) carbon cycle and the biological/physical carbon cycle. They consider how human activities disturb the carbon cycle by emitting carbon dioxide into the atmosphere. They discuss how engineers and scientists are working to reduce carbon dioxide emissions. Lastly, students consider how they can help the world through simple energy conservation measures.
This engineering curriculum meets Next Generation Science Standards (NGSS).

Learning Objectives

After this lesson, the student will be able to:

Identify the main differences between the geological carbon cycle and the biological/physical carbon cycle.

Describe how human activities have affected the carbon cycle.

Explain how engineers are working to understand and rebalance the carbon cycle.

Educational Standards
Suggest an alignment not listed above

Introduction/Motivation

Who can tell me what element is found in all living things? Carbon! Carbon is the essential element for life on Earth. Not only is carbon found in all living things, this element is present in the atmosphere, in layers of limestone sediment on the ocean floor, and in fossil fuels like coal. (This would be a good time to give students the Carbon Cycle Reference Sheet to help them follow along with the lesson. It would also be helpful to have several carbon-containing objects to show the students - a sea shell, a sedimentary rock (limestone), some chalk, a plant, maybe even a lump of coal.) The majority of sea shells contain carbon as calcium carbonate (CaCO ₃), or calcite, which is one of the most widely distributed minerals on the Earth's surface. It is found in sedimentary rocks (especially limestone) and in this piece of chalk that I am holding in front of you. A leafy green plant absorbs carbon dioxide from the atmosphere and uses it, combined with water from the soil, to make the substances it needs for growth.

What about coal? The carbon that is contained in a lump of coal is actually carbon from a very long time ago - a time when dinosaurs walked the Earth. Millions of years ago, much of the world was covered with thick vegetation and swamps. When the climate changed, this vegetation died and sunk underwater, where it lost all of its oxygen atoms, leaving sediment - containing a high percentage of carbon - on the ocean floor. As time passed, layers of sand and mud from the water settled over some of these sediments. The pressure of these overlying layers, as well as movements of the Earth's crust, compressed and hardened the deposits and produced coal. Coal, oil and natural gas are all carbon-containing substances that we call fossil fuels. Can anybody guess why we call them fossil fuels? That's right, because they were created millions of years ago, around the same time when fossils were formed.

Now that you have learned about some carbon-containing objects, let's talk about the carbon cycle. Can anybody explain what a cycle is? A cycle is a sequence of changing states that produces a final state identical to the original one. So, the carbon cycle can be described as the exchange of carbon between the land, the oceans, the atmosphere and the Earth's interior. There are two types of carbon cycles that we are going to learn about.

The first carbon cycle is the geological carbon cycle, which has been occurring over the past 4.5 billion years since our planet was born. In the geological carbon cycle, carbon moves between rocks and minerals, the oceans and the atmosphere. The processes of weathering, erosion and volcanic activity are the forces that actually move the carbon around in this cycle. This cycle can take millions of years to come full circle, and it is happening continuously all around us.

In contrast, it only takes a few days to thousands of years for the second type of carbon cycle, the biological/physical cycle, to come full circle. This is a much shorter time period than the geologic carbon cycle, and depends on which type of biological/physical carbon cycle you are looking at - carbon as it goes through the atmosphere, biosphere, hydrosphere or geosphere. Did you ever think that you might have a carbon cycle occurring inside your own body? Well, you do, and your body depends on it! When we eat, we ingest carbon in the form of carbohydrates and proteins. In our cells, the carbon combines with oxygen in our blood to produce the energy we need. Have you ever taken a deep breath after eating a big meal? Well, you are actually exhaling carbon, or carbon dioxide, as a waste product of digestion.

So, the geological carbon cycle and the biological/physical carbon cycles are the two types of cycles we are going to consider today. Fortunately, nature does a very good job at balancing these two carbon cycles - she works hard to make sure that too much carbon does not accumulate in one place. It is important that we as humans help nature do this. Over the past 100 years, humans have been upsetting the carbon cycle by adding ever-increasing amounts of carbon into the atmosphere in the form of carbon dioxide, or CO ₂. One way we release carbon into the atmosphere is by burning fossil fuels for energy to light our houses, drive our cars and even play our stereos.

Many people believe that burning fossil fuels and adding extra carbon into the atmosphere is causing a problem known as global warming. Global warming is the observed increase in the average temperatures of the Earth's atmosphere and oceans. Sure, it is okay if the Earth's temperatures rise above normal levels for a few days; however, when temperatures continue to rise over long periods of time, the Earth will start to change. This type of climate change can negatively affect human health, animal health and the environment by disturbing ecosystems, causing drought and changing crop growing seasons.

Engineers are working to reduce the carbon emissions into the atmosphere by developing technologies that use less fuel and are more sensitive to the balance of the carbon cycles. We as consumers of energy can also make a big difference by conserving energy. What are some ways that we can conserve energy? (Allow students time to brainstorm and call out answers.) That's right - we can remember to turn off our lights, computers and stereos. We can take shorter showers, ride a bike or walk when we can, and adjust our thermostats a little bit during the winter (heater) and summer (air conditioner), and just as important, we can talk to our family about recycling.

Lesson Background and Concepts for Teachers

Carbon (C) is the building block of all living things and is the fourth most abundant element in the universe after hydrogen (H), helium (He), and oxygen (O). On Earth, carbon cycles through the atmosphere, land, ocean and the Earth's interior. The global carbon cycle can be divided into two categories: the geological, which spans millions of years, and the biological/physical, which spans shorter time scales (days to thousands of years).

The Geological Carbon Cycle

All of the carbon that cycles through the Earth's systems today was actually present 4.5 billion years ago, when our solar system was born. During this time, planetesimals (small bodies that formed the solar nebula) and carbon-containing meteorites bombarded the Earth's surface. The result of the collision between these objects and the Earth was a steady increase of the carbon content of the solid Earth, which has made life here possible.

In the geological carbon cycle, carbon moves between rocks and minerals, the Earth's oceans, and the atmosphere. Carbon dioxide in the atmosphere reacts with different minerals to form the mineral calcium carbonate (limestone) through a process called weathering. Limestone is dissolved (eroded) by rainwater and carried to the oceans, where it precipitates out of the ocean water and forms layers of sediment on the ocean floor. As the Earth's plates move through the process of tectonics, these sediments are subducted (taken away) under the continents. The tremendous amount of heat and pressure beneath the Earth's surface causes the limestone to melt and react with other minerals, releasing CO ₂ in the process. Through volcanic eruptions, this carbon dioxide is re-released into the atmosphere. Nature's balance between weathering, subduction, erosion and volcanic activity is very important in controlling CO ₂ concentrations in the atmosphere.

The Biological/Physical Carbon Cycle

In contrast to the geological carbon cycle, which can take millions of years to come full circle, the biological/physical carbon cycle takes much less time (days to thousands of years). The biological/physical carbon cycle can be described as the process by which carbon is exchanged between the four main carbon reservoirs - the atmosphere, biosphere, hydrosphere and geosphere. These four main reservoirs of carbon are interconnected by pathways of exchange. Over the past 100 years, we have been upsetting the biological/physical carbon cycle by emitting unnatural amounts of CO ₂ into the atmosphere.

Carbon in the Atmosphere - Carbon exists naturally in the Earth's atmosphere primarily as the gas carbon dioxide (CO ₂) and makes up about 0.04% of the total gas composition in the atmosphere. Other atmospheric gases that contain carbon are methane and chloroflourocarbons, which are artificial (human-produced) gases. These three gases are typically referred to as greenhouse gases, whose rising concentration is thought to contribute to global warming.

As shown in Figure 3, carbon is transferred to the atmosphere from the biosphere primarily through respiration and the burning of biomass.

Much carbon is transferred from the biosphere to the atmosphere through respiration. Our respiratory system consists of the airways, the lungs and the respiratory muscles that control the movement of air (oxygen) into and out of the body. Within the lungs, molecules of oxygen and CO ₂ are exchanged between the inhaled gas and the blood. The respiratory system oxygenates the blood and removes carbon dioxide from the circulation, which is released into the atmosphere when we exhale, as illustrated in Figure 4.

Biomass is also an important part of the carbon cycle. In the energy production industry, biomass refers to living and recently living biological material (i.e., trees, plants and animal matter) which can be used as fuel to produce energy. All living (or once-living) organisms contain carbon. When the biological matter is combusted, the carbon contained in the biological matter is released back into the atmosphere. For example, dry wood is about 50% carbon. When we burn a bundle of wood, energy is released as heat. This combustion process also produces CO 2 (along with methane, carbon monoxide and smoke), which is released into the atmosphere. Although biomass is a renewable fuel, it still contributes to global warming when the amount of biomass removed from the biosphere is not replaced by an equal amount of vegetation. Both deforestation (the removal of forest cover, either intentionally - e.g., agriculture or development, or via natural consequences - e.g., forest fires, floods, etc.; see Figure 5) and the urbanization of green sites disturb the natural carbon cycle by removing biomass and ultimately transferring CO 2 into the atmosphere.

Carbon in the Geosphere - Fossil fuel is a general term for buried geologic deposits of organic material, formed from plants and animals that decayed millions of years ago. Fossil fuels such as coal, petroleum products and natural gas are sources of ancient biomass that were formed during the Carboniferous Period (360 - 286 million years ago). At that time, the land was covered with swamps filled with huge trees, ferns and other large leafy plants. As this carbon-containing vegetation died, it sank to the bottom of the swamps of oceans and formed layers of a spongy material called peat (see Figure 6).

Over many hundreds of years, the peat was covered by sand and clay and other minerals, which turned into sedimentary rock. More layers of rock piled on top and began to press down on the peat. The peat was squeezed until the water came out of it, and eventually, over millions of years, it turned into coal, oil or petroleum, and natural gas.

The utilization of fossil fuels has enabled large-scale industrial development around the world. The combustion of fossil fuels greatly disturbs the carbon cycle because they have been "out" of the cycle for a long time. The burning of fossil fuels is a major contributor to the rising carbon dioxide levels in the atmosphere. Figure 7 shows the prediction of how global carbon emissions from fossil fuels will continually increase the Earth's temperatures over the next 300 years.

Carbon in the Biosphere - Carbon is found everywhere in the biosphere and plays a crucial role in the structure, biochemistry and nutrition of all living cells. All living organisms are based on the carbon atom, and they depend on the production of sugars from solar energy and carbon dioxide (photosynthesis) to produce the chemical energy that facilitates cell growth and reproduction. The most common way that carbon is transferred to the biosphere is from the atmosphere via photosynthesis.

Photosynthesis

During photosynthesis, green plants absorb solar energy (see Figure 8) and carbon dioxide from the atmosphere to produce carbohydrates (sugars). Plants "burn" these carbohydrates during respiration, which releases the energy contained in sugars to be used as fuel. Plants then release oxygen to the atmosphere, which is used for respiration by humans and other organisms.

Photosynthesis plays a crucial role in balancing the carbon cycle by absorbing CO ₂ from the atmosphere. This process is known as "carbon sequestering." For the carbon cycle, the most important plants are trees in forests and phytoplankton in the Earth's oceans. Recently, scientists and engineers have been exploring a variety of means to artificially capture and store carbon and to enhance the natural sequestration process.

Human Activity and the Carbon Cycle

Photosynthesis, respiration and CO ₂ absorption/release from the ocean surfaces are all examples of natural fluxes of carbon through the Earth's systems. Human activities, particularly fossil fuel burning and deforestation, disrupt this natural flux by releasing CO ₂ into the atmosphere. When we mine coal and extract oil from the Earth and then burn these fossil fuels for transportation, heating, cooking, electricity and manufacturing, we are effectively moving carbon more rapidly into the atmosphere than is being removed from the atmosphere naturally through the sedimentation of carbon. This causes the concentration of CO ₂ in the atmosphere to increase, which leads to global warming. Also, by clear-cutting forests to support agriculture, we are transferring carbon from living biomass into the atmosphere. Because of this, the CO 2 concentration in the atmosphere is higher than it has ever been.

Vocabulary/Definitions

atmosphere: The Earth's atmosphere is a layer of gases surrounding the planet and retained by gravity; contains roughly 78% nitrogen, 0.97% argon, 0.04% carbon dioxide; protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.

In the energy production industry, biomass refers to living and recently living biological material which can be used as fuel for industrial production.

The outermost part of the Earth's shell, including land, surface rocks and the water within which life occurs.

carbon cycle: The carbon cycle can be described as the exchange of carbon between the land, the oceans, the atmosphere and the Earth's interior.

fossil fuel: Fossil fuels such as coal, petroleum products and natural gas are sources of ancient biomass that were formed millions of years ago from the decay of plant and animal matter.

The solid part of the Earth which is mostly rock and regolith (a layer of loose, heterogeneous material covering solid rock); the main divisions of the geosphere are the crust, mantle and core.

global warming: The observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades.

photosynthesis: The process by which green plants create energy by absorbing solar energy and carbon dioxide from the atmosphere to produce carbohydrates (sugars). Plants "burn" these carbohydrates during respiration, which releases the energy contained in sugars to be used as fuel. Plants then release oxygen to the atmosphere, which is used for respiration by humans and other organisms.

respiration: The process by which an organism obtains energy through the reaction of oxygen with glucose to give water, carbon dioxide and ATP (energy).

Associated Activities

Dinosaur Breath - Students investigate how the carbon cycle has been occurring for millions of years and is necessary for life on Earth. They also learn about the danger of heavy CO2 emissions into the atmosphere and why engineers are working to understand the carbon cycle and reduce CO2 emissions.

Lesson Closure

Today we learned that carbon is a very important part of our Earth. In fact, carbon makes life on Earth possible and exists in many different forms. What are some carbon-containing objects? That's right - seashells, plants, the atmosphere and coal. We also learned about the carbon cycle, which can be described as the exchange of carbon between the land, the oceans, the atmosphere and the Earth's interior. There are two carbon cycles to keep in mind: 1) the geological carbon cycle started billions of years ago, when our solar system was born. In the geological carbon cycle, carbon moves between rocks and minerals, the world's oceans, and volcanoes, which release carbon into the atmosphere. 2) In contrast, the biological/physical carbon cycle takes much less time (days to thousands of years). In this shorter cycle, carbon is exchanged between the atmosphere, biosphere, hydrosphere and geosphere. Some ways in which carbon is released into the atmosphere are: respiration, burning of biomass, deforestation and combustion of fossil fuels.

Can anyone tell me how human activities have been releasing too much carbon into the atmosphere? Yes, activities such as fossil fuel combustion and deforestation, are releasing unnatural amounts of carbon dioxide into the atmosphere. Today, people are concerned that the high level of CO ₂ in the atmosphere is contributing to global climate change. Engineers are working to rebalance the carbon cycle by reducing CO ₂ emissions. For example, environmental engineers are studying how to remove carbon from the atmosphere (carbon sequestration), and mechanical and electrical engineers design buildings, homes, cars and appliances that use less energy. How can you help engineers and scientists solve the global problem of climate change? You can remember to turn off the lights, computers and stereos when you are finished, take shorter showers, ride a bike or walk, and talk to your family about recycling and other energy conservation measures. Global warming is not a problem that we can leave for the scientists and engineers - solving this problem requires everyone working to save energy and reduce our consumption of energy.

Attachments

Assessment

Pre-Lesson Assessment

Know / Want to Know / Learn (KWL) Chart: Create a classroom KWL chart to help organize learning about a new topic. On a large sheet of paper or on the classroom board, draw a chart with the title "The Carbon Cycle" Draw three columns titled, K, W and L, representing what students Know about the carbon cycle, what they Want to know about the carbon cycle and what they L earned about the carbon cycle. Fill out the K and W sections during the lesson introduction as facts and questions emerge. Fill out the L section at the end of the lesson.

Post-Introduction Assessment

Reference Sheet: With the students, review the attached Carbon Cycle Reference Sheet. Suggest that students keep the sheet handy in their desks, folders or journals.

List it! Have students make a list of all the everyday things they can think of that would help conserve the amount of carbon being emitted into the atmosphere.

Lesson Summary Assessment

Think Like an Engineer! Engineers are working to rebalance the carbon cycle by reducing CO ₂ emissions. For example, environmental engineers are studying how to remove carbon from the atmosphere, and mechanical and electrical engineers are working to design buildings, homes, cars and appliances that use less energy. Engineers are also working to create technologies to capture and store carbon found in forests, oceans and soils. Have the students work in pairs to brainstorm a new invention that would help reduce carbon emissions into the atmosphere by reducing the energy used by people during an everyday activity (such as washing clothes, cooking a meal or driving a car).

Global Warming Quiz: Ask the students the following questions:

What does not contribute to global warming?

1. Burning trees

2. The hole in the ozone layer

3. Industrial pollutants

4. Auto emissions

(Answer: b; the atmosphere traps heat from the sun, much like a greenhouse. The ozone hole lets harmful ultraviolet rays in but does not contribute to global warming.)

What are greenhouse gases?

1. Other words for inert gases

2. Fuel used by farmers

3. Vapors rising off greenhouses

4. Heat-trapping atmospheric gases

(Answer: d; the primary greenhouse gases are water vapor, carbon dioxide, methane and ozone.)

Which activity does not help conserve energy?

1. Recycling

2. Using a power strip for electronics

3. Driving an electric car

4. Leaving a computer on

(Answer: d; save money and reduce emissions by turning off electronics when not in use.)

Does global warming mean that every place on Earth is getting warmer?

1. No, just the summers are warmer

2. No, but the world average is rising

3. Yes, every spot on Earth is hotter

4. No, only certain spots are hotter

(Answer: b; experts estimate that the average temperature will rise 2.5 to 10.4 degrees Fahrenheit by 2100.)

Lesson Extension Activities

Educational Poster: Have students work individually or in small groups to create posters to educate their peers about global warming and climate change. Students can research the top contributors to global warming to create a bar graph or pie chart emphasizing what percentage each contributes. Ask students to draw/write examples of ways that they can make a difference through energy efficiency and conservation. Students might find the attached Carbon Cycle Reference Sheet helpful for this exercise. This could also be assigned as homework.

Additional Multimedia Support

Games, links, climate animations and teaching materials: https://archive.epa.gov/climatechange/kids/index.html

References

Energy Information Administration, U.S. Department of Energy, Energy Kid's Page, "Energy Facts," accessed May 29, 2007. http://www.eia.doe.gov/kids/energyfacts/sources/renewable/images/photosynthesis1.gif

U.S. Department of Health and Human Services, Office on Women's Health, National Women's Health Information Center (NWHIC), GirlsHealth.gov, Body - Becoming a Woman, "Learn about your whole body - from your heart to your bones," March 2006, accessed May 25, 2007. http://www.childrencomefirst.com

U.S. Environmental Protection Agency, Kids Site, October 23, 2006, accessed May 29, 2007. http://www.epa.gov/

University of California, Lawrence Livermore National Laboratory, May 24, 2007, accessed May 29, 2007. https://publicaffairs.llnl.gov/news/news_releases/2005/images/climate_change375x275s.jpg

Wilson, Jim. National Aeronautics and Space Administration, accessed May 25, 2007. http://www.nasa.gov/images/content/104882main_gorilla-pic4-high.jpg

Wilson, Jim. National Aeronautics and Space Administration, accessed May 25, 2007. http://earthobservatory.nasa.gov/

Contributors Lauren Cooper; Malinda Schaefer Zarske; Janet Yowell

Copyright © 2007 by Regents of the University of Colorado

Supporting Program Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Last modified: April 18, 2018

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Students are introduced to the concept of energy cycles by learning about the carbon cycle. They learn how carbon atoms travel through the geological (ancient) carbon cycle and the biological/physical carbon cycle. They consider how human activities disturb the carbon cycle by emitting carbon dioxide into the atmosphere.

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MS-LS2-3 Teaching Bundle: Matter Cycles Matter: The Case of Carbon (Middle School) | NASA Wavelength Digital Library

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MS-LS2-3 Teaching Bundle: Matter Cycles Matter: The Case of Carbon (Middle School) | NASA Wavelength Digital Library

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MS-LS2-3 Teaching Bundle: Matter Cycles Matter: The Case of Carbon (Middle School)

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Designed for middle school classrooms, these resources work together as a 5E lesson sequence to build understanding about the carbon cycle and its importance to our changing climate. This bundle supports NGSS performance standard MS-LS2-3. Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.