The Carbon Cycle: a full term of science
Ten ready-to-teach lessons for Year 9 Earth and space sciences. Print this pack and the term is prepared: every lesson comes with a step-by-step plan, the questions to ask, a student worksheet, cut-out cards, game cards or exit tickets, an assessment kit and worked answers.
Start here: five minutes to Monday
- Skim the term at a glance on the next page.
- Print the lesson you need. Each lesson is three A4 sheets: plan, worksheet, and cards or tickets.
- Gather the few items under “You need” on the plan. Most come from the science prep room or the supermarket.
- Open the free interactive unit on your board or projector. Every plan tells you which picture to show and when.
- Teach straight from the plan. Timings, talk prompts, misconceptions and worked answers are all on the one page.
For any Year 9 science teacher
The pack suits an Earth science specialist and a teacher working outside their own subject alike: each plan explains the idea in plain words, lists the misconceptions students bring, and gives worked answers. The big idea of the term: Earth’s carbon is shared between four spheres, the air, living things, water and rock, and it is never made or lost; it only moves. Photosynthesis takes carbon dioxide out of the air into living things, respiration and combustion return it, the ocean dissolves it, and over millions of years shells and buried plants lock it into rock. Each process is an interaction between two spheres.
Two ways to run each lesson
Every lesson works as one 60-minute block, or as two 30-minute sessions; the split point is marked in every plan. Look ahead: Lesson 2 needs fresh spinach and a bright lamp, Lesson 4 needs three glass jars of different sizes and trays of sand, and Lesson 6 needs a bottle of soda water kept cold and one kept warm.
Safety and care in one look
Eye protection goes on whenever vinegar, indicator or a flame is used. Tea lights stand in trays of sand, long hair is tied back, and glass jars stay where they are until cool. Syringes have no needles. Balloons can be swapped for small zip bags for anyone with a latex allergy. Nothing in the science room is tasted, even the soda water.
The term at a glance
One lesson a week for a term. Each lesson stands on the ones before it, so run them in order where you can.
| # | Lesson | Students learn and do | You need (in short) |
|---|---|---|---|
| 1 | Where is Earth’s carbon? | Place twelve carbon stores in the four spheres, and test six materials for carbonate with vinegar | Vinegar, chalk, a shell, marble, granite, charcoal, sand |
| 2 | Photosynthesis: air into plants | Float spinach leaf discs in light and dark, with and without baking soda, to show plants take in carbon dioxide | Spinach, baking soda, syringes without needles, a lamp |
| 3 | Respiration: back to the air | Catch the gas from yeast in balloons, and compare three bottles | Dried yeast, sugar, small bottles, balloons |
| 4 | Combustion | Time a tea light under three jars, and work out the carbon dioxide made by burning fuel | Tea lights, three jars, sand trays |
| 5 | Joining the spheres | Sort twelve processes by what they do to the air, and draw the carbon cycle | The process cards |
| 6 | The ocean’s carbon | Test soda water with indicator, and measure how fast warm and cold soda water lose their gas | Soda water, universal indicator, a balance |
| 7 | Reading the air | Graph sixty years of carbon dioxide measurements, and link the rise to combustion | The worksheet |
| 8 | Slow carbon | Rebuild how coal and limestone form from cards, and compare the fast and slow parts of the cycle | The journey cards |
| 9 | A carbon atom’s journey | Play the carbon atom game with a die, and record the spheres and processes on the way | Dice, the station cards |
| 10 | Show what we know | Trace the carbon of a forest through a bushfire and regrowth, sit the final check and play the class quiz | The task and check, the interactive unit |
How the sequence builds
Lesson 1 finds where carbon is stored in the four spheres. Lessons 2 to 4 measure the three key processes: photosynthesis takes carbon out of the air, and respiration and combustion put it back. Lesson 5 joins the processes into the cycle, Lesson 6 adds the ocean, and Lesson 7 reads sixty years of measurements of the air. Lesson 8 follows the slow carbon locked in rock, Lesson 9 sends a single atom round the whole cycle, and Lesson 10 brings it together.
Curriculum links (Australian Curriculum V9)
The whole term teaches the Science Understanding descriptor AC9S9U03 quoted on the cover. The lessons also work these Science Inquiry and Human Endeavour descriptors:
Assessment in this pack
- Every plan ends with “Answers and look-fors”: what meeting the idea sounds like in a Year 9 voice, with working.
- The assessment sheet near the front has a class observation checklist and a three-level rubric.
- Lesson 10 is the summative pair: the forest and bushfire task, plus the “Show what we know” check.
Materials for the whole term
One gathering session covers all ten lessons, and most of it is already in the science prep room or the supermarket. Three things are worth doing ahead: buy fresh spinach the day before Lesson 2, find three glass jars of different sizes for Lesson 4, and put one bottle of soda water in the fridge and one in a warm place before Lesson 6.
| Lesson | You need |
|---|---|
| 1 | for each pair: vinegar in a dropper bottle, and small pieces of chalk, seashell, marble, granite, charcoal and washed river sand on a tray; eye protection and paper towel |
| 2 | for each group: fresh spinach leaves, a drinking straw to punch discs, a 10 mL syringe without a needle, three clear cups, baking soda, a drop of dishwashing liquid, a bright lamp or a sunny window, a box to make a dark place, and a timer |
| 3 | for each group: three small plastic bottles, three balloons (or small zip bags), dried yeast, sugar, warm (not hot) water, a funnel, string and a ruler |
| 4 | tea lights, three glass jars of about 250 mL, 500 mL and 1 L, trays of sand, a long lighter for the teacher, a timer and eye protection |
| 5 | the process cards from this pack, one set per pair; scissors and glue sticks |
| 6 | a bottle of soda water kept cold and one kept warm, two clear cups, universal indicator with its colour chart, a balance reading to 0.1 g, tap water and eye protection |
| 7 | the worksheet only; the interactive unit open on the board |
| 8 | the journey cards from this pack, one set per pair; scissors and glue sticks |
| 9 | a die for each player; the station cards from this pack, cut out and placed around the room |
| 10 | the task and the final check; the interactive unit open for the class quiz |
The one-trip list
- From the prep room: dropper bottles, eye protection, syringes without needles, universal indicator, a balance, trays and timers.
- From the supermarket: vinegar, chalk, fresh spinach, baking soda, dishwashing liquid, dried yeast, sugar, balloons, tea lights and soda water.
- From home or the garden: a seashell, a piece of charcoal, three glass jars and some washed river sand.
- For Lesson 9: one die for each player.
Safety and care in one look
- Eye protection for vinegar, indicator and flames; wipe up spills.
- Tea lights in trays of sand, long hair tied back; glass jars stay put until cool.
- Syringes have no needles; small zip bags replace balloons for anyone with a latex allergy.
- Nothing in the science room is tasted, even the soda water.
Assessment without extra work
The term assesses itself. Every lesson plan ends with worked answers and look-fors, and Lesson 10 is the summative pair: the task, in which students trace the carbon of a forest through a bushfire and its regrowth, and the final check. This sheet is the place to note what you see along the way.
The three levels
| Idea | Working towards | At standard | Beyond |
|---|---|---|---|
| Spheres and stores | names where some carbon is stored | places carbon stores in the four spheres and gives the form carbon takes in each | explains why a test such as the vinegar fizz detects only some stores |
| Key processes | names photosynthesis, respiration or combustion | describes how photosynthesis, respiration and combustion move carbon, with evidence from practical work | explains each as an interaction between two spheres, with the direction of the flow |
| Representing the cycle | draws some arrows between spheres | draws and labels a carbon cycle that links all four spheres | shows fast and slow parts of the cycle, and where the cycle is out of balance |
| Data | reads values from a table | graphs and describes trends, such as carbon dioxide in the air since 1960 | calculates rates of change and links them to causes |
| Working scientifically | follows the method | uses controls and repeat trials, and records with care | evaluates a model or a game for what it shows and what it leaves out |
Class observation checklist
| Name | Spheres | Processes | Cycle | Data | Investigating |
|---|---|---|---|---|---|
A tick a lesson is plenty; the Lesson 10 task and check fill the gaps.
Word wall cards
Cut out the cards and build the wall as the words arrive: carbon cycle, atmosphere, biosphere, hydrosphere, geosphere, carbon store and carbonate in Lesson 1; photosynthesis in Lesson 2; respiration and decomposer in Lesson 3; combustion and fossil fuel in Lesson 4; dissolve in Lesson 6; ppm in Lesson 7; sediment, limestone, fast cycle and slow cycle in Lesson 8.
the movement of carbon between the four spheres
the layer of air around Earth
all the living things on Earth
all of Earth’s water: oceans, rivers, lakes and ice
the rock and soil of Earth
a place where carbon is held, such as wood, seawater or rock
carbon joined with oxygen in rocks and shells, such as limestone
plants using light to make sugar from carbon dioxide and water
living things releasing energy from sugar, giving off carbon dioxide
burning: a fuel reacting with oxygen, giving off carbon dioxide
coal, oil or natural gas, formed from living things over millions of years
a fungus or bacterium that breaks down dead material
to spread into a liquid, as carbon dioxide does in water
parts per million: how many particles in every million
layers of mud, sand or shells that settle and may harden into rock
rock made mostly of calcium carbonate from old shells
carbon moving through living things and the air in days to years
carbon moving through rock over millions of years
Dear families
This term in science, Year 9 studies the carbon cycle: how the same carbon atoms move between the air, living things, the oceans and rock. Students investigate the three key processes that move carbon, photosynthesis, respiration and combustion, and how each one links two of Earth’s spheres.
Along the way your student will test rocks and shells for stored carbon, float spinach leaf discs that photosynthesise, catch the gas from yeast in a balloon, time a candle in a jar, graph sixty years of measurements of the air, and follow a single carbon atom around the planet with a die.
Try this at home
- Put a little baking soda in a cup and add vinegar. The gas is carbon dioxide: where else does it come from in your home?
- Open a cold and a warm bottle of soda water. Which fizzes more, and why?
- Watch bread dough rise. What are the yeast doing, and what is the gas?
- Find something in your home that stores carbon from the biosphere, and something that stores carbon from the geosphere.
What to ask your scientist
- What are the four spheres, and where is carbon stored in each?
- Which processes take carbon out of the air, and which put it back?
- Why does burning coal or petrol add carbon to the air faster than nature removes it?
- How can a carbon atom in a car’s exhaust end up in a tree, and then in a shell?
A small note on care: students wear eye protection when using vinegar, indicator or flames, candles stand in trays of sand, and nothing in the science room is tasted.
Warm regards,
The Year 9 science team
Printed from the free seegongsik The Carbon Cycle teaching pack · seegongsik.com/au/y9/earth-and-space/AC9S9U03/pack
Where is Earth’s carbon?
Earth’s carbon is shared between four spheres. In the atmosphere it is mostly carbon dioxide gas; in the biosphere it is built into the bodies of living things; in the hydrosphere it is dissolved in water; and in the geosphere it is locked in rocks such as limestone, and in coal, oil and gas. Most of Earth’s carbon is in rock. Students place twelve carbon stores in their spheres, then test six materials with vinegar: a fizz shows carbonate, carbon held with oxygen in rocks and shells, giving off carbon dioxide.
We are learning to
- name Earth’s four spheres and describe what each is made of,
- identify carbon stores in each sphere, and the form the carbon takes,
- test materials for carbonate, and say what the test cannot show.
Success criteria
- I can place twelve carbon stores in their spheres.
- I can explain why charcoal does not fizz, even though it is almost pure carbon.
You need
- for each pair: vinegar in a dropper bottle, and small pieces of chalk, seashell, marble, granite, charcoal and washed river sand on a tray; eye protection,
- the worksheet (next sheet), one per student, and the exit tickets (third sheet).
Safety: eye protection on; vinegar stings eyes; wipe up spills and wash hands afterwards.
Lesson flow (about 60 minutes)
| 5 min | Carbon all around Ask: “Your body, the air you breathe and the pencil in your hand all contain carbon. Where else is it?” |
| 10 min | On the board Show the board (see the box). Add carbon cycle, the four spheres and carbon store to the word wall. |
| 15 min | Twelve stores Students write the sphere for each carbon store in Part A. |
| 30 min | The fizz test Pairs predict, then put two drops of vinegar on each material and watch for bubbles with their eyes level with the tray. They record in Part B and answer Part C. Add carbonate to the word wall. Ask: “Charcoal is nearly pure carbon. Why did it not fizz?” |
Running two half-sessions instead? Do the opening, the board and the stores in Session A, and the fizz test in Session B.
Watch for these ideas
- “Carbon is only in living things.” It is in all four spheres, and most of it is in rock.
- “All carbon is carbon dioxide.” Carbon is also in sugar, wood, shells, limestone, coal and much more.
- “No fizz means no carbon.” Vinegar shows only carbonate; charcoal is carbon that is not carbonate.
Make it easier, make it bigger
- Easier: write the four spheres on the board with a picture beside each, and sort the stores together for the first four.
- Bigger: a seagrass meadow takes carbon from seawater and buries some of it in the sea floor. Which spheres does a seagrass meadow link?
Answers and look-fors
- Part A: carbon dioxide in the air, atmosphere; limestone cliffs, geosphere; the wood of a river red gum, biosphere; carbon dioxide dissolved in the ocean, hydrosphere; the body of a whale, biosphere; coal in the ground, geosphere; a meadow of seagrass, biosphere; methane in the air, atmosphere; oil deep under the sea floor, geosphere; carbon dioxide breathed out by a runner, atmosphere; carbon dissolved in river water, hydrosphere; natural gas trapped in rock, geosphere.
- Part B: fizzed: chalk, a seashell, marble chip; no fizz: granite chip, charcoal, washed river sand.
- Part C: 1. Carbon dioxide: the carbonate reacts with the acid in the vinegar. 2. They are made of calcium carbonate, carbon stored with oxygen. 3. Charcoal is carbon that is not joined to oxygen as carbonate, so vinegar does not react with it. 4. Shells built by sea creatures pile up on the sea floor and harden into limestone; heat and pressure can turn limestone into marble.
- Bigger: the biosphere (the living seagrass), the hydrosphere (the seawater it takes carbon from) and the geosphere (the sea floor it buries carbon in).
- Exit tickets: 1. Atmosphere, biosphere, hydrosphere, geosphere. 2. The geosphere. 3. Carbonate, giving off carbon dioxide.
Where is Earth’s carbon?
A. Twelve carbon stores
Write the sphere for each store: atmosphere, biosphere, hydrosphere or geosphere.
| Carbon dioxide in the air | |
| Limestone cliffs | |
| The wood of a river red gum | |
| Carbon dioxide dissolved in the ocean | |
| The body of a whale | |
| Coal in the ground |
| A meadow of seagrass | |
| Methane in the air | |
| Oil deep under the sea floor | |
| Carbon dioxide breathed out by a runner | |
| Carbon dissolved in river water | |
| Natural gas trapped in rock |
B. The fizz test
| Material | Prediction: fizz or not? | Result |
|---|---|---|
| Chalk | ||
| A seashell | ||
| Granite chip | ||
| Marble chip | ||
| Charcoal | ||
| Washed river sand |
C. Questions
Exit tickets
Cut out one ticket for each student.
1. Name Earth’s four spheres.
2. Which sphere holds most of Earth’s carbon?
3. What does a fizz with vinegar show?
1. Name Earth’s four spheres.
2. Which sphere holds most of Earth’s carbon?
3. What does a fizz with vinegar show?
1. Name Earth’s four spheres.
2. Which sphere holds most of Earth’s carbon?
3. What does a fizz with vinegar show?
1. Name Earth’s four spheres.
2. Which sphere holds most of Earth’s carbon?
3. What does a fizz with vinegar show?
Photosynthesis: air into plants
Photosynthesis moves carbon from the atmosphere into the biosphere: plants take in carbon dioxide and water and, using the energy of light, make glucose and give off oxygen. Leaf discs let students watch it happen. Discs punched from a spinach leaf have air in the spaces inside them; drawing the air out with a syringe makes them sink. In water with baking soda, which supplies dissolved carbon dioxide, and in bright light, the discs photosynthesise, the spaces fill with oxygen and the discs float up. Students run three cups, two of them controls, and count the floating discs every two minutes.
We are learning to
- describe photosynthesis as a flow of carbon from the air into living things,
- use controls to show what a process needs,
- graph counts over time and read a half-way time from them.
Success criteria
- I can graph the three cups and find when half the discs in cup A floated.
- I can say what each control cup shows.
You need
- for each group: fresh spinach leaves, a drinking straw to punch discs, a 10 mL syringe without a needle, three clear cups, baking soda, a drop of dishwashing liquid, a bright lamp or a sunny window, a box for a dark place, and a timer,
- the worksheet (next sheet), one per student, and the exit tickets (third sheet).
Safety: the syringes have no needles. Keep water away from the lamp and its cord, and wipe up spills.
Lesson flow (about 60 minutes)
| 5 min | A tree’s mass Ask: “A gum tree can weigh many tonnes. Where did most of that mass come from: the soil, the water or the air?” |
| 10 min | On the board Show the board (see the box). Add photosynthesis to the word wall. |
| 30 min | Three cups Stir a pinch of baking soda and one drop of dishwashing liquid into a cup of water. Punch 30 discs with the straw. Put 10 discs and some solution in the syringe, cover the tip with a finger and pull the plunger to draw the air out of the discs; repeat until they sink. Cup A: 10 sunk discs in the solution, in bright light. Cup B: the same, in a dark box. Cup C: 10 discs sunk in plain water with the detergent, in bright light. Count the floating discs every 2 minutes for 12 minutes. Ask: “What is each of cups B and C there to test?” |
| 15 min | What the cups say Students graph the counts in Part B and answer Part C. |
Running two half-sessions instead? Do the opening, the board and the cups in Session A, and Parts B and C in Session B.
Watch for these ideas
- “Plants get their food from the soil.” Plants make their own food, and most of a plant’s dry mass is carbon taken from the air.
- “Plants breathe in carbon dioxide instead of respiring.” Plants photosynthesise in light, and they respire all the time, as animals do.
- “The discs float because light makes them lighter.” They float because oxygen from photosynthesis fills the spaces inside them.
Make it easier, make it bigger
- Easier: set up cup A only, and use the example counts for the two controls.
- Bigger: in cup C, one disc floated by minute 10. Suggest two reasons, and how you would test one of them.
Answers and look-fors
- Part A, example: in cup A half the discs floated at about 6.7 minutes and all 10 by 12 minutes; cup B, none; cup C, 1.
- Part B: cup A rises slowly, then steeply, then levels off at 10; cup B stays at zero; cup C stays near zero.
- Part C: 1. Cup B shows that light is needed; cup C shows that carbon dioxide is needed. 2. Oxygen, made by photosynthesis, filled the spaces in the discs. 3. The carbon dioxide came from the baking soda in the water, and its carbon became part of the sugar in the leaf: from outside the plant into the biosphere. 4. In the leaves of every plant on Earth, carbon dioxide from the air is built into sugar, moving carbon from the atmosphere to the biosphere.
- Bigger: a little carbon dioxide from the air was dissolved in the tap water, or the disc’s own respiration made some, or some air was left in it. Boiled and cooled water, which holds less gas, would test the first idea.
- Exit tickets: 1. Carbon dioxide and water, and light. 2. From the atmosphere to the biosphere. 3. Oxygen.
Photosynthesis: air into plants
A. Discs floating (out of 10)
| Time (min) | 0 | 2 | 4 | 6 | 8 | 10 | 12 |
|---|---|---|---|---|---|---|---|
| Cup A: light, baking soda, example | 0 | 0 | 1 | 4 | 7 | 9 | 10 |
| Cup B: dark, baking soda, example | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Cup C: light, plain water, example | 0 | 0 | 0 | 0 | 0 | 1 | 1 |
| Cup A, ours | |||||||
| Cup B, ours | |||||||
| Cup C, ours |
B. Graph
Plot the three cups on the same axes, join each set of points, and add a key. Mark when half the discs in cup A floated.
C. Questions
Exit tickets
Cut out one ticket for each student.
1. What does a plant need for photosynthesis?
2. Photosynthesis moves carbon from which sphere to which?
3. Which gas do plants give off in photosynthesis?
1. What does a plant need for photosynthesis?
2. Photosynthesis moves carbon from which sphere to which?
3. Which gas do plants give off in photosynthesis?
1. What does a plant need for photosynthesis?
2. Photosynthesis moves carbon from which sphere to which?
3. Which gas do plants give off in photosynthesis?
1. What does a plant need for photosynthesis?
2. Photosynthesis moves carbon from which sphere to which?
3. Which gas do plants give off in photosynthesis?
Respiration: back to the air
Every living thing respires: its cells break down sugar to release energy, and carbon dioxide is given off. Respiration moves carbon from the biosphere back to the atmosphere, every moment, in plants, animals, fungi and bacteria alike. Decomposers, the fungi and bacteria that break down dead leaves and bodies, return much of the carbon this way. Students catch the gas from yeast, a single-celled fungus, in balloons over three bottles: yeast with sugar, yeast alone, and sugar alone.
We are learning to
- describe respiration as a flow of carbon from living things back into the air,
- run a test with two controls and measure a change over time,
- explain what the controls show about what respiration needs.
Success criteria
- I can graph the three balloons and explain the difference between them.
- I can say where the carbon in the balloon came from and where it is going.
You need
- for each group: three small plastic bottles, three balloons (or small zip bags), dried yeast, sugar, warm (not hot) water, a funnel, string and a ruler,
- the worksheet (next sheet), one per student, and the exit tickets (third sheet).
Care: use warm tap water, not hot; offer zip bags to anyone with a latex allergy; nothing is tasted; wash hands afterwards.
Lesson flow (about 60 minutes)
| 5 min | Rising dough Ask: “Bread dough with yeast in it grows bigger in a warm place. What could be filling it up?” |
| 10 min | On the board Show the board (see the box). Add respiration and decomposer to the word wall. |
| 30 min | Three bottles Into each bottle pour 100 mL of warm water. Bottle 1: a teaspoon of yeast and two of sugar. Bottle 2: a teaspoon of yeast only. Bottle 3: two teaspoons of sugar only. Swirl, stretch a balloon over each neck, and measure round each balloon with string every 5 minutes for 20 minutes. Record the growth in Part A. While waiting, students write a prediction and start Part C. Ask: “Why does bottle 3 matter if we already know sugar cannot make gas on its own?” |
| 15 min | Graph and explain Students graph the three balloons in Part B and finish Part C. |
Running two half-sessions instead? Do the opening, the board and the bottles in Session A, and Parts B and C in Session B.
Watch for these ideas
- “Respiration is breathing.” Breathing moves air in and out of lungs; respiration is the chemical process in every cell, including in yeast and plants.
- “Plants do not respire.” Plants respire all the time, day and night.
- “The gas came from the sugar dissolving.” Bottle 3 shows that sugar alone makes no gas: the yeast did it.
Make it easier, make it bigger
- Easier: set up bottle 1 only, and use the example readings for the controls.
- Bigger: plan a valid test of whether the temperature of the water changes how fast the yeast respires. What would you change, measure and keep the same?
Answers and look-fors
- Part A, example: after 20 minutes the balloon on bottle 1 had grown by 24 cm round, bottle 2 by 3 cm, bottle 3 not at all.
- Part B: bottle 1 rises quickly and then more slowly; bottle 2 rises a little; bottle 3 stays at zero.
- Part C: 1. Carbon dioxide. 2. Bottle 2 shows that yeast needs sugar to make much gas; bottle 3 shows that sugar alone makes none. 3. The carbon came from the sugar, which the yeast broke down; when the balloon is let down, it goes into the atmosphere. 4. Plants respire too, and so do the decomposers in the soil, so respiration happens wherever there is life.
- Bigger: change the water temperature (for example 10, 25 and 40 °C); measure the growth of the balloon in 20 minutes; keep the same amounts of yeast, sugar and water, the bottles and the timing.
- Exit tickets: 1. Carbon dioxide. 2. From the biosphere to the atmosphere. 3. Every living thing: plants, animals, fungi and bacteria.
Respiration: back to the air
A. Growth round each balloon (cm)
| Time (min) | 0 | 5 | 10 | 15 | 20 |
|---|---|---|---|---|---|
| Bottle 1: yeast and sugar, example | 0 | 8 | 15 | 20 | 24 |
| Bottle 2: yeast only, example | 0 | 1 | 2 | 2 | 3 |
| Bottle 3: sugar only, example | 0 | 0 | 0 | 0 | 0 |
| Bottle 1, ours | |||||
| Bottle 2, ours | |||||
| Bottle 3, ours |
B. Graph
Plot the three bottles on the same axes, join each set of points, and add a key.
C. Questions
Exit tickets
Cut out one ticket for each student.
1. Which gas does respiration give off?
2. Respiration moves carbon from which sphere to which?
3. Which living things respire?
1. Which gas does respiration give off?
2. Respiration moves carbon from which sphere to which?
3. Which living things respire?
1. Which gas does respiration give off?
2. Respiration moves carbon from which sphere to which?
3. Which living things respire?
1. Which gas does respiration give off?
2. Respiration moves carbon from which sphere to which?
3. Which living things respire?
Combustion
Combustion is burning: a fuel reacts with oxygen from the air, giving off heat and light, water vapour and carbon dioxide. Burning wood or a bushfire returns carbon from the biosphere to the atmosphere; burning coal, oil and gas returns carbon from the geosphere, carbon that had been buried for millions of years. Each kilogram of carbon that burns becomes about 3.7 kg of carbon dioxide, because each carbon atom joins two oxygen atoms taken from the air. Students time a tea light under three jars of different sizes to show that burning uses part of the air, then work out the carbon dioxide made by burning fuel.
We are learning to
- describe combustion as a flow of carbon from a fuel into the air,
- show with repeated trials that burning uses part of the air,
- calculate the mass of carbon dioxide made by burning fuel.
Success criteria
- I can find the mean burning time for each jar and explain the pattern.
- I can calculate the carbon dioxide from burning petrol, and explain why it weighs more than the fuel’s carbon.
You need
- tea lights, three glass jars of about 250 mL, 500 mL and 1 L, trays of sand, a long lighter for the teacher, a timer and eye protection,
- the worksheet (next sheet), one per student, and the exit tickets (third sheet).
Safety: eye protection on; long hair tied back and sleeves rolled up; the teacher lights each tea light in its tray of sand. After the flame goes out, leave the jar where it is for a minute to cool.
Lesson flow (about 60 minutes)
| 5 min | A candle in a jar Ask: “If I cover a burning candle with a jar, what will happen? Why?” |
| 10 min | On the board Show the board (see the box). Add combustion and fossil fuel to the word wall. |
| 25 min | Three jars Groups lower each jar over a lit tea light and time until the flame goes out, three trials for each jar, letting fresh air back into the jar between trials. They record the times in Part A and look for mist inside the jar. Ask: “Why do we let fresh air into the jar between trials?” |
| 20 min | Carbon in, carbon out Students find the means, then work through Parts B and C. |
Running two half-sessions instead? Do the opening, the board and the jars in Session A, and Parts B and C in Session B.
Watch for these ideas
- “The flame used up all the air.” It used much of the oxygen; the rest of the air, mostly nitrogen, is still in the jar.
- “Burning destroys the fuel.” Its atoms join oxygen and leave as carbon dioxide and water; no atom is destroyed.
- “The carbon dioxide must weigh less than the fuel.” Each carbon atom gains two oxygen atoms, so the gas weighs more than the carbon it came from.
Make it easier, make it bigger
- Easier: time the 500 mL jar only, and use the example times for the others.
- Bigger: the inside of the jar turns misty. What is the mist, and which atoms in the wax did it come from?
Answers and look-fors
- Part A, example means: 250 mL 7.3 s, 500 mL 15 s, 1000 mL 30 s. Twice the air gives about twice the time.
- Part B: 1. About 3.7 kg. 2. 7 × 2.3 = 16.1 kg of carbon dioxide for each 100 km. 3. 16.1 × 100 = 1610 kg, about 1.6 tonnes in a year.
- Part C: 1. Burning needs the oxygen in the air, and a bigger jar holds more. 2. Water, made from the hydrogen in the wax. 3. From oil, so from the geosphere (a soy wax tea light would be from the biosphere). 4. Burning fossil fuels moves carbon that was stored in the geosphere for millions of years into the atmosphere, in a few seconds.
- Bigger: tiny drops of water; the wax is made of carbon and hydrogen, and the hydrogen joins oxygen to make water.
- Exit tickets: 1. Carbon dioxide and water. 2. From the geosphere to the atmosphere. 3. Oxygen.
Combustion
A. How long does the flame last? (seconds)
| Jar | Trial 1 | Trial 2 | Trial 3 | Mean | Ours |
|---|---|---|---|---|---|
| 250 mL, example | 7 | 8 | 7 | ||
| 500 mL, example | 15 | 14 | 16 | ||
| 1000 mL, example | 29 | 31 | 30 |
B. Carbon in, carbon dioxide out
A carbon atom has a mass of 12 and an oxygen atom 16, so carbon dioxide (one carbon, two oxygen) has a mass of 44 for every 12 of carbon. Burning a litre of petrol makes about 2.3 kg of carbon dioxide.
C. Questions
Exit tickets
Cut out one ticket for each student.
1. Name two substances made when a fuel burns.
2. Burning coal moves carbon from which sphere to which?
3. Which gas from the air does burning use?
1. Name two substances made when a fuel burns.
2. Burning coal moves carbon from which sphere to which?
3. Which gas from the air does burning use?
1. Name two substances made when a fuel burns.
2. Burning coal moves carbon from which sphere to which?
3. Which gas from the air does burning use?
1. Name two substances made when a fuel burns.
2. Burning coal moves carbon from which sphere to which?
3. Which gas from the air does burning use?
Joining the spheres
Put the processes together and they make a cycle: every process is a bridge between two spheres, or a step within one. Some take carbon out of the air, such as photosynthesis and the ocean dissolving carbon dioxide. Some put it back, such as respiration, decomposition, fires, volcanoes and burning fossil fuels. Others move carbon without the air at all: an animal eating a plant, plankton taking up dissolved carbon, shells settling into rock. Students sort twelve processes by what they do to the air, then draw their own carbon cycle on a four-sphere frame.
We are learning to
- classify processes by the way they move carbon,
- name the two spheres each process links, and the direction of the flow,
- represent the carbon cycle as a labelled diagram.
Success criteria
- I can sort the twelve processes and name the spheres each one links.
- I can draw a carbon cycle that joins all four spheres with labelled arrows.
You need
- the process cards (third sheet), one set per pair, with scissors and glue sticks,
- the worksheet (next sheet), one per student.
Lesson flow (about 60 minutes)
| 5 min | In and out Ask: “Lessons 2 to 4 measured three processes. Which took carbon out of the air, and which put it back?” |
| 10 min | On the board Show the board (see the box). |
| 20 min | Sort the processes Pairs cut out the cards, lay down the three grey heading cards and sort the processes under them. The piles are not the same size. They record the letters in Part A. Ask: “For each card, ask: does the air gain carbon, lose it, or play no part?” |
| 25 min | Draw the cycle Students glue or copy at least eight processes onto the frame in Part B as arrows between the spheres, then answer Part C. |
Running two half-sessions instead? Do the opening, the board and the sort in Session A, and the drawing and Part C in Session B.
Watch for these ideas
- “The carbon cycle has a start and an end.” It is a loop: carbon keeps moving, and no atom is made or lost.
- “Decomposition is not part of the cycle.” Decomposers respire the carbon in dead things back into the air.
- “Each arrow goes only one way.” Some spheres swap carbon both ways, such as the air and the ocean.
Make it easier, make it bigger
- Easier: draw the cycle with six arrows: photosynthesis, respiration, combustion, dissolving, eating and shells to rock.
- Bigger: add a thicker arrow wherever you think carbon moves fastest, and explain one choice.
Answers and look-fors
- Part A: takes carbon out of the air B, H, I; puts carbon into the air A, D, F, G, K; moves carbon without the air C, E, J, L.
- Links: A biosphere to atmosphere; B atmosphere to biosphere; C within the biosphere; D geosphere to atmosphere; E hydrosphere to biosphere; F biosphere to atmosphere; G biosphere to atmosphere; H atmosphere to hydrosphere; I atmosphere to biosphere; J biosphere to geosphere; K geosphere to atmosphere; L hydrosphere to geosphere.
- Part B: arrows from the atmosphere to the biosphere (photosynthesis) and the hydrosphere (dissolving); from the biosphere to the atmosphere (respiration, decomposition, fires), to the geosphere (burial) and within itself (eating); from the hydrosphere to the biosphere (plankton) and the geosphere (shells); from the geosphere to the atmosphere (fossil fuels, volcanoes).
- Part C: 1. Respiration, by every living thing, all the time. 2. Combustion of fossil fuels and volcanoes. 3. The atoms only move between spheres; none are made or destroyed, so the same carbon keeps going round.
Joining the spheres
A. Our sort
| Takes carbon out of the air | |
| Puts carbon into the air | |
| Moves carbon without the air |
B. Our carbon cycle
Draw arrows between the spheres for at least eight processes. Name the process on each arrow.
C. Questions
What does each process do to the air?
Cut out the cards. Lay down the three grey heading cards, then sort the processes under them.
Teacher note: the piles are not the same size. The answer letters and the spheres each process links are in the plan.
The ocean’s carbon
The ocean holds far more carbon than the air and all living things together, and it swaps carbon dioxide with the air at its surface all the time. It has taken up about a quarter of the carbon dioxide people have added to the air. Two things about dissolving matter for the cycle. Cold water holds more gas than warm water, so a warming ocean takes up less. And dissolved carbon dioxide makes a weak acid, which lowers the pH of seawater a little and makes it harder for corals and shellfish to build their shells. Students test soda water, water with carbon dioxide dissolved in it under pressure, with universal indicator, then measure how fast cold and warm soda water lose their gas.
We are learning to
- describe how carbon dioxide moves between the atmosphere and the hydrosphere,
- investigate how temperature changes how much gas water can hold,
- connect the ocean’s carbon to living things that build shells.
Success criteria
- I can compare the mass lost by cold and warm soda water, and explain the difference.
- I can explain why a warmer ocean takes up less carbon dioxide.
You need
- a bottle of soda water kept cold and one kept warm, two clear cups, universal indicator with its colour chart, a balance reading to 0.1 g, tap water and eye protection,
- the worksheet (next sheet), one per student, and the exit tickets (third sheet).
Safety: eye protection on; universal indicator stains and stings eyes; nothing is drunk, even the soda water; wipe up spills.
Lesson flow (about 60 minutes)
| 5 min | Flat soft drink Ask: “Why does an open bottle of soft drink go flat faster on a hot day?” |
| 10 min | On the board Show the board (see the box). Add dissolve to the word wall. |
| 15 min | Indicator Add three drops of universal indicator to a cup of tap water and to a cup of soda water. Students match each colour to the chart and record the pH in Part A. |
| 30 min | Cold and warm Pour 100 mL of cold soda water into a cup on the balance and record the mass every 2 minutes for 10 minutes; repeat with warm soda water. Students record the mass lost in Part B, graph it and answer Part C. Ask: “The cups lose mass, but nothing is spilt. Where is the mass going?” |
Running two half-sessions instead? Do the opening, the board and the indicator in Session A, and the cold and warm test in Session B.
Watch for these ideas
- “Dissolved carbon dioxide is gone.” It is still there, spread through the water, and it can come back out.
- “Warm water dissolves more of everything.” Warm water dissolves more sugar, but it holds less gas.
- “The ocean is turning into acid.” Seawater is still slightly basic; its pH is falling a little, which is enough to make shell building harder.
Make it easier, make it bigger
- Easier: weigh each cup only at the start and after 10 minutes, and graph the example readings.
- Bigger: corals on the Great Barrier Reef build skeletons of calcium carbonate. Explain how carbon dioxide added to the air could affect them, linking three spheres.
Answers and look-fors
- Part A: tap water about pH 7 (green); soda water about pH 5 (yellow to orange), a weak acid.
- Part B, example: in 10 minutes the cold soda water lost 0.4 g and the warm soda water lost 1.4 g, 3.5 times as much.
- Part C: 1. Dissolved carbon dioxide forms a weak acid. 2. Carbon dioxide gas leaving the water into the air. 3. Warm water holds less gas, so the gas leaves it faster. 4. A warmer ocean holds less carbon dioxide, so it takes less out of the air, and more stays in the atmosphere.
- Bigger: more carbon dioxide in the air (atmosphere) dissolves in the sea (hydrosphere) and lowers its pH; corals (biosphere) then find it harder to build their calcium carbonate skeletons, which in time become reef rock (geosphere).
- Exit tickets: 1. From the atmosphere to the hydrosphere, or back. 2. Cold water. 3. It lowers the pH of the water a little.
The ocean’s carbon
A. Indicator
| Water | Colour | pH from the chart |
|---|---|---|
| Tap water | ||
| Soda water |
B. Mass lost by 100 mL of soda water (g)
| Time (min) | 0 | 2 | 4 | 6 | 8 | 10 |
|---|---|---|---|---|---|---|
| Cold, example | 0.0 | 0.1 | 0.2 | 0.3 | 0.3 | 0.4 |
| Warm, example | 0.0 | 0.4 | 0.7 | 1.0 | 1.2 | 1.4 |
| Cold, ours | ||||||
| Warm, ours |
C. Questions
Exit tickets
Cut out one ticket for each student.
1. Dissolving carbon dioxide links which two spheres?
2. Which holds more dissolved gas: cold water or warm water?
3. What does dissolved carbon dioxide do to the pH of water?
1. Dissolving carbon dioxide links which two spheres?
2. Which holds more dissolved gas: cold water or warm water?
3. What does dissolved carbon dioxide do to the pH of water?
1. Dissolving carbon dioxide links which two spheres?
2. Which holds more dissolved gas: cold water or warm water?
3. What does dissolved carbon dioxide do to the pH of water?
1. Dissolving carbon dioxide links which two spheres?
2. Which holds more dissolved gas: cold water or warm water?
3. What does dissolved carbon dioxide do to the pH of water?
Reading the air
Since 1958 an observatory high on the Mauna Loa volcano in Hawaii has measured the carbon dioxide in the air, far from cities and forests, and since 1976 the Cape Grim station in north-west Tasmania has measured some of the cleanest air on Earth. Both records show the same pattern. Each year the carbon dioxide rises and falls a little with the seasons, as the forests of the northern half of the world grow in spring and summer and drop their leaves in autumn. Underneath that wiggle it climbs year after year, matching the carbon added by burning fossil fuels and clearing forests. Students graph 60 years of rounded annual means, measure the rise in each decade, and link the trend to the processes of the cycle.
We are learning to
- graph a long data set and describe its trend,
- calculate the change in each decade and compare the changes,
- link a trend in the atmosphere to the processes of the carbon cycle.
Success criteria
- I can graph carbon dioxide against year and work out the rise in each decade.
- I can explain the rise, and the small yearly wiggle, with processes of the carbon cycle.
You need
- the worksheet (next sheet), one per student, and the exit tickets (third sheet).
Lesson flow (about 60 minutes)
| 5 min | An invisible change Ask: “How could anyone know how much carbon dioxide was in the air in 1960?” |
| 10 min | On the board Explain ppm, parts per million, and the two stations, then show the board (see the box). Add ppm to the word wall. |
| 25 min | Sixty years Students plot the means in Part A, join the points, and work out the rise in each decade in Part B. Ask: “Is the line straight, or is it bending? What does a bend mean here?” |
| 20 min | Why is it rising? Students answer Part C, then share answers to question 1. |
Running two half-sessions instead? Do the opening, the board and the graph in Session A, and the rises and Part C in Session B.
Watch for these ideas
- “A few ppm a year is too small to matter.” Over decades it adds up: about 97 ppm in 60 years here.
- “The yearly wiggle shows the rise is just natural.” The wiggle is the seasons; the trend underneath keeps climbing.
- “One station could be wrong.” It could, which is why stations far apart, such as Mauna Loa and Cape Grim, are compared: they agree.
Make it easier, make it bigger
- Easier: plot only 1960, 1990 and 2020 first, then add the rest.
- Bigger: the rise in each decade is getting bigger. Predict the mean for 2030, and say what your prediction assumes.
Answers and look-fors
- Part A: the points climb from 317 to 414 ppm, and the line bends upwards: the rise is speeding up.
- Part B: 1960 to 1970, 9 ppm; 1970 to 1980, 13 ppm; 1980 to 1990, 15 ppm; 1990 to 2000, 16 ppm; 2000 to 2010, 20 ppm; 2010 to 2020, 24 ppm. In all 97 ppm, a mean of 16.2 ppm a decade.
- Part C: 1. Burning fossil fuels and clearing forests put carbon into the air faster than photosynthesis and the ocean take it out. 2. In the northern growing season, photosynthesis takes carbon dioxide in; in autumn and winter, respiration and decay give it back. 3. The stations are far from cities and forests, so they measure the air itself, and two stations far apart agree.
- Bigger: for example, about 442 ppm, if each decade’s rise keeps growing by a few ppm; the prediction assumes the burning of fossil fuels keeps growing as before.
- Exit tickets: 1. Parts per million. 2. It has risen, faster each decade. 3. Burning fossil fuels (and clearing forests).
Reading the air
A. Carbon dioxide at Mauna Loa (rounded annual means)
| Year | 1960 | 1970 | 1980 | 1990 | 2000 | 2010 | 2020 |
| CO₂ (ppm) | 317 | 326 | 339 | 354 | 370 | 390 | 414 |
B. The rise in each decade
| 1960 to 1970 | 1970 to 1980 | 1980 to 1990 | 1990 to 2000 | 2000 to 2010 | 2010 to 2020 |
|---|---|---|---|---|---|
C. Questions
Exit tickets
Cut out one ticket for each student.
1. What does ppm stand for?
2. How has the carbon dioxide in the air changed since 1960?
3. Name one human activity that adds carbon to the air.
1. What does ppm stand for?
2. How has the carbon dioxide in the air changed since 1960?
3. Name one human activity that adds carbon to the air.
1. What does ppm stand for?
2. How has the carbon dioxide in the air changed since 1960?
3. Name one human activity that adds carbon to the air.
1. What does ppm stand for?
2. How has the carbon dioxide in the air changed since 1960?
3. Name one human activity that adds carbon to the air.
Slow carbon
The carbon cycle runs at two speeds. In the fast cycle, carbon moves between the air, living things and the surface of the sea in seconds, seasons or a lifetime. In the slow cycle, carbon is locked into rock: swamp plants buried under mud become coal over millions of years, and the shells of sea creatures harden into limestone. It comes back out just as slowly, through weathering and volcanoes. Burning coal, oil and gas takes carbon from the slow cycle and puts it into the fast cycle in minutes, faster than the slow cycle can take it back. Students rebuild the journeys to coal and to limestone from cards, and sort processes by their speed.
We are learning to
- describe how carbon is locked into the geosphere as coal and limestone,
- compare the speeds of the fast and slow parts of the cycle,
- explain why burning fossil fuels changes the balance of the cycle.
Success criteria
- I can put both journeys in order and say which spheres each one passes through.
- I can explain why carbon from fossil fuels builds up in the air.
You need
- the journey cards (third sheet), one set per pair, with scissors and glue sticks,
- the worksheet (next sheet), one per student.
Lesson flow (about 60 minutes)
| 5 min | Old sunlight Ask: “People call coal “buried sunshine”. What could they mean?” |
| 10 min | On the board Show the board (see the box). Add sediment, limestone, fast cycle and slow cycle to the word wall. |
| 25 min | Two journeys Pairs cut out the twelve cards, sort them into the two journeys and put each in order. They write the letters in Part A and glue one journey into their books. Ask: “Which card in each journey takes the longest? Which sphere is the carbon in then?” |
| 20 min | Fast and slow Students mark each process fast or slow in Part B and answer Part C. |
Running two half-sessions instead? Do the opening, the board and the journeys in Session A, and Parts B and C in Session B.
Watch for these ideas
- “Coal and oil are made from dinosaurs.” Coal formed mostly from ancient swamp plants, and oil mostly from tiny sea life.
- “Fossil fuels will form again soon.” They take millions of years to form; we burn them in decades.
- “Rock carbon is out of the cycle for good.” Weathering and volcanoes slowly return it.
Make it easier, make it bigger
- Easier: give the first card of each journey to start from.
- Bigger: write a journey of six cards for a carbon atom in oil, from tiny sea life to a car’s exhaust, and swap with another pair.
Answers and look-fors
- Part A: from swamp to coal J, C, L, E, H, B; from sea to limestone D, G, I, A, K, F.
- Part B: a leaf takes in carbon dioxide, seconds; burning a tonne of coal, minutes to hours; swamp plants become coal, millions of years; a fallen leaf rots in the soil, months to a few years; shells harden into limestone, millions of years; a gum tree grows and dies, a hundred years or more: fast are those in seconds to a lifetime; slow are those in millions of years.
- Part C: 1. Coal: atmosphere, biosphere, geosphere, then atmosphere again; limestone: atmosphere, hydrosphere, biosphere, geosphere, then out again. 2. Burning moves carbon from the slow cycle into the air in minutes, but the slow cycle takes millions of years to lock it away again, so it builds up in the fast cycle. 3. The carbon in coal was taken from the air by plants long ago, using the energy of sunlight.
Slow carbon
A. The two journeys in order
| From swamp to coal | ||||||
| From sea to limestone |
B. Fast or slow?
| Process | How long it takes | Fast or slow cycle? |
|---|---|---|
| A leaf takes in carbon dioxide | seconds | |
| Burning a tonne of coal | minutes to hours | |
| Swamp plants become coal | millions of years | |
| A fallen leaf rots in the soil | months to a few years | |
| Shells harden into limestone | millions of years | |
| A gum tree grows and dies | a hundred years or more |
C. Questions
Journey cards
Cut out the twelve cards. Sort them into two journeys of six, from swamp to coal and from sea to limestone, then put each in order.
Teacher note: the answer letters are in the plan. Each journey begins with carbon in the air or the sea and ends with it set free again.
A carbon atom’s journey
A single carbon atom can spend a moment in the air, a century in a tree or millions of years in rock. In this game each student is a carbon atom. Six station cards stand around the room: the air, a plant, an animal, the soil, the ocean, rock and fossil fuel. At each station the atom rolls a die and follows the card: it stays, or it moves on by a named process. Students record ten rolls, pool the class results to see where carbon tends to gather, and judge what the game shows well and what it leaves out.
We are learning to
- trace a carbon atom through the four spheres, naming each process on the way,
- use pooled class results to describe where carbon is held longest,
- evaluate a model of the carbon cycle.
Success criteria
- I can record ten moves, each with its process and the two spheres it links.
- I can name one way the game matches the real cycle and one way it does not.
You need
- a die for each player; the station cards (third sheet), cut out and placed at six spots around the room,
- the worksheet (next sheet), one per student.
Lesson flow (about 60 minutes)
| 5 min | Old atoms Ask: “Some of the carbon in your body may once have been in a dinosaur’s breath. How could that be?” |
| 10 min | On the board Show the board (see the box), then explain the rules: roll, read the card, write down the roll, then walk to the next station or stay. |
| 25 min | Play Spread the students evenly across the six stations to start. Each rolls ten times, recording every roll in Part A. Ask: “Which station was hardest to leave? Why might that be true of the real cycle?” |
| 20 min | Class results Tally where every atom finished, fill Part B together, then students answer Part C. |
Running two half-sessions instead? Do the opening, the board and the game in Session A, and the class results and Part C in Session B.
Watch for these ideas
- “Every carbon atom follows the same route.” Atoms take many routes; the cycle is a web of paths, not one loop.
- “Carbon gets used up on the way.” It only moves; every atom is still somewhere at the end.
- “Each roll is the same length of time.” A roll stands for seconds in the air but a very long time in rock.
Make it easier, make it bigger
- Easier: play six rolls instead of ten, in pairs, with one recorder.
- Bigger: rewrite one station card so that it matches the real cycle better, and explain your change.
Answers and look-fors
- Part A: any journey that follows the cards, with a process and two spheres for every move, such as the air to a plant by photosynthesis.
- Part B: the rock and fossil fuel station keeps an atom on 4 of the 6 faces of the die, the most of any station, so atoms tend to gather there as the game goes on; the air keeps an atom on 3 of 6.
- Part C: 1. Rock and fossil fuel: in the real cycle carbon stays in rock for millions of years. 2. For example: real moves do not happen by chance on a die, each station stands for very different lengths of time, and the real cycle has more paths, such as the ocean giving carbon to shells directly. 3. Burning fossil fuels: it takes carbon out of the slowest station far faster than the game allows.
A carbon atom’s journey
A. My ten rolls
| Roll | Station | Number | Process (or stayed) | Next station |
|---|---|---|---|---|
| 1 | ||||
| 2 | ||||
| 3 | ||||
| 4 | ||||
| 5 | ||||
| 6 | ||||
| 7 | ||||
| 8 | ||||
| 9 | ||||
| 10 |
B. Where did the class finish?
| The air | A plant | An animal | The soil | The ocean | Rock and fossil fuel |
|---|---|---|---|---|---|
C. Questions
Carbon atom game: station cards
Cut out the six cards and place them around the room. At each station, roll the die and do what the card says.
Show what we know
The term comes together. In the task, students follow the carbon of an example patch of eucalypt forest: how it got into the trees, what a bushfire does with it, where it goes afterwards, and how regrowth takes it back. They calculate the carbon dioxide released and the years of regrowth needed, and draw the forest’s own carbon cycle across the four spheres. Then they sit the eight-question final check, and the class plays the unit quiz as a game on the board.
We are learning to
- apply photosynthesis, respiration and combustion to a real place,
- calculate with the masses of carbon and carbon dioxide,
- represent a carbon cycle that links all four spheres.
Success criteria
- I can explain each stage of the forest’s story with the right process and spheres.
- I can answer the final check on my own.
You need
- the task (next sheet) and the final check (third sheet), one each per student,
- the interactive unit open on the board for the quiz; mini whiteboards if you have them.
Lesson flow (about 60 minutes)
| 5 min | Three processes Point to the word wall and recall the three key processes. Ask: “For each one: which sphere does the carbon leave, and which does it enter?” |
| 25 min | After the fire Students complete the task on their own. Read the story aloud first. |
| 20 min | Final check Students complete the final check on their own. |
| 10 min | Class quiz Run the unit quiz on the board as a class game (see the box). |
Running two half-sessions instead? Do the processes and the task in Session A, and the final check and the quiz in Session B.
Watch for these ideas
- Students who say the fire destroys the carbon: ask where each atom goes.
- Students who name combustion of wood as a geosphere process: wood is part of the biosphere.
- Students who treat regrowth and coal burning as the same: regrowth takes carbon back in decades; coal’s carbon took millions of years to lock away.
Make it easier, make it bigger
- Easier: give the processes as a list (photosynthesis, combustion, respiration, decomposition, dissolving) to choose from.
- Bigger: the same patch of forest is cleared for good instead of burning. How does the story change?
Answers and look-fors
- Task: 1. Photosynthesis took carbon dioxide from the air and built it into wood: atmosphere to biosphere. 2. 60 tonnes of carbon (30% of 200). 3. 60 × 44 ÷ 12 = about 220 tonnes of carbon dioxide. 4. Decomposers respire the carbon in the dead wood back into the air; some charcoal and ash stay in the soil, and rain washes some into creeks and the sea. 5. 60 ÷ 3 = 20 years. 6. Coal’s carbon was locked in the geosphere for millions of years and is not taken back by regrowth in a lifetime.
- Diagram: atmosphere to biosphere (photosynthesis); biosphere to atmosphere (combustion in the fire, respiration by decomposers and by the trees); biosphere to geosphere (charcoal and ash in the soil); geosphere to hydrosphere (ash washed into creeks and the sea).
- Final check: 1. The geosphere. 2. Photosynthesis. 3. The biosphere to the atmosphere. 4. The geosphere and the atmosphere. 5. Cold water. 6. Each carbon atom joins two oxygen atoms from the air, so the carbon dioxide weighs more. 7. The slow cycle. 8. Burning fossil fuels and clearing forests add carbon to the air faster than photosynthesis and the ocean can take it out.
- Bigger: with no regrowth, the carbon released is not taken back, so the air keeps it, and the land stores less carbon from then on.
After the fire
An example patch of eucalypt forest stores 200 tonnes of carbon in its trees. A bushfire burns 30% of it. In the years after, the burnt trees and fallen branches rot, rain washes ash into a creek, and new growth sprouts from the trunks and from seeds. The regrowing forest takes up about 3 tonnes of carbon a year.
The forest’s carbon cycle
Draw arrows between the spheres for the fire, the rotting, the ash and the regrowth. Name the process on each arrow.