carbon cycle science - eli · pdf filecarbon cycle science 15 ... petroleum, and natural gas...

Teaching Notes and Answer Keys

Carbon Cycle Science

15

Subject area: Science / Biology / Earth Science

Topic focus: The Carbon Cycle

Learning Aims:

• what carbon is and why it is important• carbon is in all four of the Earth’s spheres• how carbon moves from one sphere to another• how carbon cycles work in both the short term and

the long term • carbon sources and carbon sinks• how humans influence / change the carbon cycle

and contribute to climate changes• what a carbon footprint is and how to calculate it

Skills:

Reading: defining and describing; scanning for specificinformation; researching and evaluating informationWriting: taking notes; writing an essaySpeaking: planning and making a presentation

Carbon, p. 16

1 Review with your students that carbon is a commonelement on Earth: - have students brainstorm some of the things in their

daily lives that contain carbon (e.g. trees, cars,paper, meat, plastic objects, etc.) make a list ofthese items on the board

- double check by eliciting a list of the things that don’tcontain carbon (e.g. metals, table salt, water)

- have students work in pairs or small groups followingthe instructions

- have them go through the definitions, compare anddiscuss

- let students consider the fact that there is a limitedamount of carbon on Earth, but that the carboncontained in any one thing doesn’t stay there forever.

TR 3 - CLIL_Carbon Cycle_1

The Carbon Cycle, pp. 16-172 Focus on the picture and go over it with the students,

pointing out how carbon moves from one place toanother. Point out that the possible solutions orinformation can be found in the text on p. 17. Make surethe students realize that carbon atoms move from onething to another in the carbon cycle. Explain that partsof the carbon cycle happen very quickly, like whenplants take in carbon dioxide from the atmosphere forphotosynthesis, but that other parts of the carbon cyclehappen very slowly, like when carbon is released fromnatural geological processes.

2 1 Fossil fuel burning, 2 Photosynthesis, 3 Decomposition, 4 Respiration, 5 Biomass, 6 Aquatic biomass, 7 Coal & oil, 8 Sediments.

Balance at Risk, pp. 17-193 Spend some time analysing the picture in activity 3 in

order to elicit from students the difference betweensource (origin) and sink (container/depository).

4 First have students fill in the headings, next have themread and listen to the text in activity 4.

5 Have students work in pairs or small groups to fill in thechart.

6 Plan enough lesson time to let students organise theposter as suggested in activity 6 in order to let themvisualise what they have learnt about alterations of thecarbon cycle; give them time to prepare for apresentation to the class. The task should be assignedbefore the lesson so that students can gather andorganize visual materials for the poster.


4 1 Human Alterations, 1.1 Burning Fossil Fuels, 1.2 Deforestation,1.3 Farming;2 Dangers; 3 Researching ways to find equilibrium.

5 Model answersCarbon Sources: Deforestation, Decomposing plants, Volcanoesand other volcanic phenomena, Using cars,, Photosynthesis,Heating, Transportation, Building houses (constructions sites),Cement manufacturing, Farming, Cell respiration, Preparingmeals.Carbon Sinks: Oceans, Plants, Soil, The Earth, Lakes,Underground rocks

Your Carbon Footprint, p. 197+8 Encourage students to plan individual actions to cut

down on emissions (e.g. turn down heating by one ortwo degrees, etc.)

Check your Knowledge, p. 20The Carbon Cycle Test (test A) is focused on subjectknowledge, while the crossword activity (test B) checksstudents’ subject- specific vocabulary.

A Model answers1 It’s the constant flowing of carbon between the Earth’sspheres; 2 It combines sunlight, water, and carbon dioxide toproduce oxygen and glucose (sugar / energy) throughchlorophyll; 3 Terrestrial and aquatic plants; 4 Throughrespiration because they use the oxygen produced by the plants;5 Non-renewable energy sources (oil, coal and natural gas)formed from the compressed sediments of decomposed plantsand animals that died long ago; 6 By combustion and volcaniceruption; 7 Burning fossil fuels, deforestation, cattle and ricefarming; 8 Burned trees, stability and temperature of soil andtillage; 9 Global warming, i.e., temperature increases, rising sealevel, changes in rainfall patterns, increased storms andorganism extinction; 10 Alternative energy sources (solar, wind,etc.), reconsidering your lifestyle (driving less, saving electricity,etc.), carbon capture and storage.

B 1 greenhouse effect, 2 carbon, 3 carbon cycle, 4 biosphere, 5 carbon footprint, 6 lithosphere, 7 atmosphere, 8 carbon sink, 9 carbon dioxide, 10 hydrosphere.

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16 Photocopiable Introduction to CLIL – Change Up! © ELI

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Science – Carbon Cycle

Carbon

The Carbon Cycle2 Look at this picture then

read the text on p. 17 andfill in the blank labels withwords from the box.

Aquatic BiomassBiomassCoal and OilDecompositionFossil Fuel BurningPhotosynthesisRespirationSediments

The EarthSystemBiogeochemistry studies how ourplanet’s spheres interact. The carboncycle is one of the processes whichinvolves the whole of the Earthsystem: it describes the storage andexchange of carbon between theEarth’s spheres.

CO2 inAtmosphere

CO2 inHydrosphere

CO2 inBiosphere

CO2 inLithosphere

Limestone

1

2

3

4 5

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8

1 What is the answer to the following questions? Match them to the answers below.Next, read and listen to the answers provided and compare them with your own.

1 What is Carbon (C)?

2 Where is Carbon found?

3 What is the Carbon Cycle and why is it important?

�� A Carbon is an element that is essential for life as we know it. Put very simply, living organisms takecarbon from their environment. When they die, carbon is returned to the non-living environment. Thecarbon cycle includes the processes of production, consumption, decomposition and storage of carbon.

�� B Carbon is a naturally abundant, non-metallic element that occurs in all organic compounds and canbe found in all known forms of life.

�� C Carbon exists in the non-living environment as: carbon dioxide (CO2) in the atmosphere anddissolved in water (forming HCO3¯, bicarbonate ion), carbonate rocks (limestone and coral =CaCO3), deposits of coal, petroleum, and natural gas derived from once-living things, dead organicmatter, e.g. humus in the soil.


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Balance at Risk

The Carbon CycleThe carbon cycle naturally consists of two parts, the terrestrial and the aquatic. In the aquatic carbon cycle carbon moves through marine ecosystems and in the terrestrial carboncycle moves through terrestrial ecosystems. The carbon cycle is based on the creation of carbondioxide (CO2), which can be found in the air in gaseous form, and in water in dissolved form. Terrestrial plants use carbon dioxide from the atmosphere to generate oxygen that sustains animallife. In much the same way, aquatic plants also generate oxygen through photosynthesis, a processby which plants and other carbon producers transform carbon dioxide and water into a complexcarbohydrate (glucose C6H12O6), under the influence of sunlight. Only plants and some bacteria havethe ability to carry out this process because they possess chlorophyll, a pigment molecule foundprimarily in green leaves, that makes it possible to “capture” solar energy and transform it.The basic chemical reaction that makes up the process of photosynthesis is:

carbon dioxide + water + solar energy —> glucose + oxygen6CO2 + 6H2O + solar energy —> C6H12O6 + 6O2

Carbon dioxide is released back into the atmosphere during respiration of carbon consumers, whichbreaks down glucose and other complex organic compounds and converts the carbon back to carbondioxide for reuse by carbon producers. Carbon that is used by producers (green plants), consumers (animals and humans) anddecomposers (fungi and bacteria) cycles fairly rapidly through air, water and biosphere. But carboncan also be stored as biomass in the roots of trees and other organic matter for many decades. Thiscarbon is released back into the atmosphere by decomposition. Not all organic matter is immediatelydecomposed. Under certain conditions dead plant matter accumulates faster than it is decomposedwithin an ecosystem. The remains are locked away in underground deposits. When layers ofsediment compress this matter, fossil fuels will be formed after many centuries. The carbon in thesefossil fuels is slowly released into the air during long-term geological processes and volcanic eruptions;it is also released during combustion processes related to human activity. In the hydrosphere, carbon dioxide can be stored in deep sea sediments and in rocks in thelithosphere. It will take a long time before this carbon dioxide will be released, through the naturalweathering of rocks or geologic processes that bring sediment to the surface of water. Carbon dioxidethat is stored in water will be present as either carbonate or bicarbonate ions; when the sun warmsup the water, carbonate and bicarbonate ions will be returned to the atmosphere as carbon dioxide.Carbon moves through two cycles. The two systems move hundreds of billions of tons of carbondioxide into and out of the atmosphere each year.

• The short-term cycle carries carbon through surface ocean water, the atmosphere, soils andvegetation, taking tens to hundreds of years to complete.

• The long-term cycle moves carbon very slowly through the atmosphere, oceans, as well as throughunderground rocks, deep-sea sediments and volcanoes.

3 Considering the text above, look carefully at this picture and take some notes to distinguish between:- Carbon sources – activities and processes that introduce carbon dioxide into the atmosphere. - Carbon sinks – places where CO2 goes after it leaves a source.

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4 Read the following text and match these headings to the appropriate paragraphs.Then listen and check.


Dangers Burning Fossil Fuels Researching ways to find equilibriumDeforestation Human Alterations Farming

A new and risky equilibriumA complete carbon cycle can take millions of years. When the cycles are in balance or‘equilibrium’, atmospheric levels of carbon remain relatively stable.1 _________________________________________There are natural fluctuations in the carbon cycle, but humans have been changing the carbon flows on earth atan unnatural rate. The major human-induced changes in the carbon cycle result in increased carbon dioxide(CO2) and methane (CH4) in the atmosphere. The largest source of this change is burning fossil fuels, but otheractions such as deforestation, cattle farming, and rice farming also contribute to this change in the carbon cycle.

1.1 _______________________________________Humans use fossil fuels such as oil, coal, and natural gas for a variety of purposes including powering ourvehicles, producing electricity, heating and cooling our buildings, and producing goods such as plastics. Whenwe burn these fossil fuels, we take carbon that has been stored underground for a very long time and put it intothe atmosphere.

1.2 _______________________________________Deforestation causes carbon to be released into the atmosphere for a number of reasons. First, trees that arecut are often burned, which immediately releases the carbon stored in the trees into the atmosphere. Second,deforestation impacts both the temperature and stability of the soil. Since soils contain a significant amount ofcarbon, changes that affect the soil can affect the carbon stored in the soil. Deforestation results in more soilerosion because trees are no longer there to stabilize the soil. Eroded soil and the carbon it contains often endup in rivers and streams and eventually in the oceans, bringing carbon from the land into the hydrosphere.Soils in deforested areas are not only eroded because of the lack of trees, but they are also often tilled foragriculture. Tillage* turns over the soil, releasing carbon dioxide gas contained in the soil to the atmosphere.

1.3 _______________________________________Cattle farming and rice farming both release methane gas to the atmosphere. This also occurs in naturalwetlands. Both cattle and rice farming are on the rise worldwide and thus these sources of greenhouse gasesare becoming more and more of a concern. Methane emissions are also especially concerning because methaneis a much stronger greenhouse gas than carbon dioxide, meaning that each molecule of methane warms theearth substantially more than each molecule of carbon dioxide.

2 _________________________________________Carbon dioxide (CO2) and methane (CH4) are ‘greenhouse gases’, that is gases which tend to raise thetemperature of a gaseous atmosphere when irradiated with UV radiation. Therefore, it has been conjectured bymany scientists that human-induced increases in atmospheric carbon levels are resulting in an artificial climatechange on our planet. This change includes temperature increases, rising sea level, changes in rainfall patterns,increased storms, and organism extinctions.

3 _________________________________________People are currently taking many different actions in an attempt to slow climate change. They areendeavouring both to lessen the amount of carbon that is emitted to the atmosphere and to take carbon out ofthe atmosphere and store it elsewhere. Some of the ways we can decrease the amount of carbon emitted into theatmosphere include driving less, using energy efficient appliances, switching to solar and wind power, andcapturing carbon from power plants and other stationary sources and pumping it underground for storage. Thisis called carbon capture and storage. People have been using this technique in oil fields for a long time.Scientists are currently researching carbon capture and storage methods to try to determine whether thistechnique can be used on a large scale. Mitigating climate change by actually taking carbon out of theatmosphere can be accomplished by several different methods. Simply planting more trees takes carbon out ofthe atmosphere, because plants take carbon from the atmosphere to perform photosynthesis. Other methods fortaking carbon dioxide out of the atmosphere include capturing carbon dioxide gas and converting it back intousable fuel. This is an ongoing research topic and although there are currently many viable options fordecreasing the amount of carbon in the atmosphere, the future may hold other possibilities as well.

___________

* Tillage: working the land by ploughing to make it ready for growing crops

Footprints, in general, can be verydestructive to delicate environmentslike nature reserves. A carbon footprintis a representation of your personalcontribution to global warming. It ismeasured by the greenhouse gasemissions that result from the choicesyou make: for instance, when youchoose to drive to school instead ofwalking or taking public transport youare choosing to emit moregreenhouse gases and are thusincreasing your footprint. Being awareof your footprint will help focusattention on what you can do todiminish the negative impacts on ourglobal environment.

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19Introduction to CLIL – Change Up! © ELI Photocopiable

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5 Fill in the chart taking into consideration your notes from activity 3 and what you read in the text in activity 4.

Carbon Sources Carbon Sinks

Electricity Generation

_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Deposits of Fossil fuels (coal, oil,etc.)

Atmosphere / air

Rivers

_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

6 Make a poster showing the alterations of the carbon cycle and its consequences for the Earth, then present it to the class.

Your Carbon Footprint7 Do you know what is meant by “carbon footprint”? Discuss your ideas with a partner. Next, read this text and

compare with your own answers.

8 Essay Writing

What can humans do to decrease the amount of carbon being released into the atmosphere?

How do you and your family use energy? How do you usually travel?

Calculate your carbon footprint athttp://www.carbonfootprint.com/carbonfootprint.html

and discuss the results: How can you reduce your carbon footprint?

You should be able to find plenty ofinformation on reducing your own carbonfootprint on the Internet.

Some suggested starting points are http://www.safeclimate.net/action/

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Check your knowledgeA The Carbon Cycle Test

1 What is the carbon cycle? 2 What does photosynthesis do in the carbon cycle?3 What are carbon producers? 4 How do carbon consumers release carbon dioxide into the air ? 5 What are fossil fuels? 6 How do fossil fuels release carbon dioxide into the atmosphere? 7 What human activities can alter the equilibrium of the carbon cycle?8 How is deforestation responsible for the release of carbon dioxide?9 What are the consequences of changes in the carbon cycle?

10 What ways have been found to lessen the amount of CO2 being released?

B Crossword 1

2

3

4

5

6 7

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9

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1 The result of excess carbon dioxide in the atmosphere causing climate changes.

2 Non-metallic chemical element found in all organic compounds.

3 The continuous process by which carbon is exchanged between the 4 spheres of the Earth system.

4 All living things.5 Refers to the amount of carbon dioxide

emitted.6 The Earth’s crust.7 Air surrounding the Earth.8 Area that absorbs carbon in water or land

and doesn’t recycle.9 Gas used in plants for photosynthesis.

10 Bodies of water on the Earth.

carbon cycle science - eli · pdf filecarbon cycle science 15 ... petroleum, and natural gas...

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