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# Where is all the carbon?

Year 9 Earth and space · The carbon cycle

<!-- Speaker note: Students identify carbon stores in each of Earth's spheres, distinguish stores from flows, and explain that carbon moves between stores without being made or destroyed (AC9S9U03, node 2). About 23 minutes (Engage and Explore 7 min · Explain 10 min · Evaluate 3 min · Typical adds 3 min, Wider about 3 min). -->

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## Today

**We are learning to** carbon is stored in every one of Earth's spheres: as carbon dioxide in the air, dissolved in the oceans, in living things and soil, and in fossil fuels and rocks. Carbon is never made or destroyed; it moves between these stores, and the carbon cycle is the map of those moves.

- I can name a carbon store in each of Earth's four spheres.
- I can explain the difference between a carbon store and a carbon flow.
- I can explain that carbon moves between stores but is never made or destroyed.

<!-- Speaker note: Before class: A concept tutorial for introducing or revising the idea. Set the width with `?width=minimum`, `typical` (default) or `wider`. It sits between What are Earth's spheres? (node 1) and Where does the carbon in a tree go? (node 3), which uses the same cycle board to switch flows on and off. Not a hinge node, but it sets up the cycle: students who confuse stores (amounts) with flows (amounts a year), or think burning destroys carbon, struggle with every later carbon lesson. Board notes: the cycle board shows four stores; rocks (the largest store) are left out because their carbon moves over millions of years. Store sizes are rounded: air about 600 GtC before industry (about 875 today), living things and soil about 2150, oceans about 38 000, fossil fuels about 1000. Boxes are not to scale. Teacher: In your own words: the four boxes with stores and two labelled flows are the evidence. -->

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## Why it matters

> The carbon atoms in your body have been in dinosaurs, in ocean water and in the air, many times over. They are billions of years old and still in use.

<!-- Speaker note: Last lesson: Earth has four spheres. This lesson follows one substance through all of them: carbon. -->

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<span style="background:#dbeafe; color:#1a1a1a; border:1.5px solid #3b82f6; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">💬 Discussion</span>

## Engage: predict

**Which of these holds the most carbon?**

- All living things on land
- The air
- Coal, oil and gas
- The oceans

<!-- Speaker note: What happens: The oceans, by far: about 38 000 billion tonnes, roughly 50 times what is in the air. (Rocks such as limestone hold even more, but that carbon moves very slowly.) Take two or three predictions before anyone runs it. -->

<!-- Speaker note: Teacher: tally the predictions. Most will say the air; the oceans are the surprise. -->

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<span style="background:#fef3c7; color:#1a1a1a; border:1.5px solid #f59e0b; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✍️ Activity</span>

## Explore it

{{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-9%2Fcarbon-stores%2Fstep-2&code=widget%3A+carbon%0Amode%3A+cycle%0A&fresh=1}}

[Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-9/carbon-stores/?full=step-2#step-2)

<!-- Speaker note: Each box is a **store** (how much carbon is there); each arrow is a **flow** (how much moves each year). Press **Run 10 years** and watch the stores. -->

<!-- Speaker note: Teacher: ask why the air's store barely moved when the arrows show large flows. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## What happened?

* The oceans, by far: about 38 000 billion tonnes, roughly 50 times what is in the air. (Rocks such as limestone hold even more, but that carbon moves very slowly.)

<!-- Speaker note: Reveal after running. Ask who predicted it, and what made them think so. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Which sphere

**Which sphere is each carbon store in?**

Groups: Atmosphere · Hydrosphere · Biosphere · Geosphere

Carbon dioxide in the air · Carbon dioxide dissolved in sea water · Carbon in trees and animals · Dead leaves and roots in soil · Coal, oil and natural gas · Limestone (calcium carbonate) rock

* Answer: Carbon dioxide in the air → Atmosphere; Carbon dioxide dissolved in sea water → Hydrosphere; Carbon in trees and animals → Biosphere; Dead leaves and roots in soil → Biosphere; Coal, oil and natural gas → Geosphere; Limestone (calcium carbonate) rock → Geosphere

<!-- Speaker note:  -->

<!-- Speaker note: Teacher: the sphere sort and the store-or-flow question are the success criteria. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Store or flow

**What is the difference between a carbon store and a carbon flow?**

- They mean the same thing
- A store is where carbon is kept; a flow is carbon moving from one store to another each year
- Stores are in the air; flows are in the ocean

* Answer: A store is where carbon is kept; a flow is carbon moving from one store to another each year

<!-- Speaker note: Stores are measured in tonnes of carbon; flows in tonnes a year. Photosynthesis is a flow from air to living things. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## A burning log

**When a log burns, what happens to its carbon?**

- It turns into energy
- It is destroyed by the fire
- It moves into the air as carbon dioxide: the same atoms, in a different store

* Answer: It moves into the air as carbon dioxide: the same atoms, in a different store

<!-- Speaker note: Carbon is never made or destroyed. Burning moves it from the biosphere to the atmosphere. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Steady

**The air's carbon stayed steady on the board, even though more than a hundred billion tonnes moved in and out each year. Why?**

- Nothing was really moving
- The board stops the air changing
- The flows into the air and out of it were balanced

* Answer: The flows into the air and out of it were balanced

<!-- Speaker note: A store stays the same when what flows in equals what flows out, like a bath with the tap on and the plug out. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Fast or slow

**Fast or slow? How long does carbon usually stay in each store?**

Groups: Fast: years to centuries · Slow: millions of years

Carbon dioxide in the air · Carbon in a gum tree · Dead leaves in the soil · A coal seam · Limestone rock

* Answer: Carbon dioxide in the air → Fast: years to centuries; Carbon in a gum tree → Fast: years to centuries; Dead leaves in the soil → Fast: years to centuries; A coal seam → Slow: millions of years; Limestone rock → Slow: millions of years

<!-- Speaker note:  -->

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<span style="background:#fef3c7; color:#1a1a1a; border:1.5px solid #f59e0b; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✍️ Activity</span>

## Elaborate: carbon in the landscape

{{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-9%2Fcarbon-stores%2Fstep-4&code=widget%3A+carbon%0Amode%3A+spheres%0A&fresh=1}}

[Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-9/carbon-stores/?full=step-4#step-4)

<!-- Speaker note: What this step is for: Placing real things into spheres checks that students can find carbon stores in a familiar scene. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Carbon everywhere

**Which of these things in a landscape store carbon?**

- Only the air
- Only the trees
- Trees, soil, the sea, the air and limestone cliffs: every sphere

* Answer: Trees, soil, the sea, the air and limestone cliffs: every sphere

<!-- Speaker note: Carbon is everywhere: it is part of every living thing, dissolved in water, in the air, and locked in rocks. -->

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<span style="background:#fef3c7; color:#1a1a1a; border:1.5px solid #f59e0b; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✍️ Activity</span>

## Elaborate: shells to stone

{{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-9%2Fcarbon-stores%2Fstep-5&code=widget%3A+carbon%0Amode%3A+cycle%0A&fresh=1}}

[Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-9/carbon-stores/?full=step-5#step-5)

<!-- Speaker note: What this step is for: Limestone made from shells links the biosphere, hydrosphere and geosphere and shows a store that changes over millions of years. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Shells to stone

**Sea creatures take carbon dissolved in water to build shells of calcium carbonate. When they die, the shells pile up and, over millions of years, become limestone. Which stores has that carbon moved through?**

- Hydrosphere → biosphere → geosphere
- Atmosphere → atmosphere
- Geosphere → biosphere → hydrosphere

* Answer: Hydrosphere → biosphere → geosphere

<!-- Speaker note: Rocks such as limestone are the largest carbon store of all, but their carbon moves out very slowly, mostly over millions of years. -->

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## Evaluate: look back

Write one sentence: "At first I thought… Now I think… because…"

**Revision summary**

- Carbon is stored in every sphere: **atmosphere** (carbon dioxide), **hydrosphere** (dissolved in the oceans), **biosphere** (living things, dead matter, soil) and **geosphere** (fossil fuels, limestone and other rocks).
- The oceans hold far more than the air; rocks hold the most of all.
- Carbon is never made or destroyed. It **flows** between stores: the **carbon cycle** is the map of those flows.
- A store stays steady when the flows into it balance the flows out.

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Exit ticket

**Name a carbon store in the hydrosphere and one in the geosphere, and one flow that moves carbon into the atmosphere.**

* Hydrosphere: carbon dioxide dissolved in the oceans. Geosphere: fossil fuels or limestone. Flow into the air: respiration, decay, burning or release from the oceans.

<!-- Speaker note: Students answer on paper or a mini whiteboard before the reveal. Anyone who cannot answer needs the main idea again next lesson. Where this leads: Next: Where does the carbon in a tree go? (photosynthesis and respiration, node 3), then fossil fuels (node 4). In class: a "carbon atom's journey" dice game around stores; dissolving carbon dioxide from breath in limewater. -->