Lesson 4

Lesson 4: Aerobic Respiration

The Word & Symbol Equations

🍬🫁⚖️🔢🔋

Learning Objectives:

Recall (2.34/2.35) – Last lesson: respiration releases energy from glucose to make ATP.
2.37 – Know the word equation and the symbol equation for aerobic respiration.

🏆 By the end I will be able to…

All: pick out the correct word equation and name the reactants and products.

Most: write the word equation, and copy the symbol equation C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O correctly.

Some: write the symbol equation from memory and explain what the big 6s mean.

Navigation: Arrow Keys or Spacebar

Teacher Print Tools – Lesson 4

⏱️ Before We Start · 60 sec

Before We Start: Respiration & ATP in 60 Seconds

New to this? Here is everything you need for today — fast. (It is all on Side A of your bridge sheet if you want it on paper.)

What happens inside a cell

Glucose + oxygen go IN → the mitochondria break glucose down using oxygen → carbon dioxide, water and ATP come OUT.

1. Respiration releases energy from glucose to make ATP — inside your cells (it is not breathing).

2. It happens in the mitochondria. Aerobic respiration uses oxygen → lots of ATP.

3. Energy is released, not made — always say ATP.

Whiteboards — 20 seconds: what two things go IN? What comes OUT? Then we go straight into today’s equations.

⭐ Fab 4

The Fab 4 – Recall to Get You Started

Instructions: Multiple choice — in your books, write the letter of the answer you think is right for each one. No calling out. Reveal when ready.

1. Energy

What does ATP give a cell?

A) A colourB) EnergyC) WaterD) A smell

✅ B) Energy. ATP is the cell's energy.

2. The gas needed

Aerobic respiration uses glucose and one gas. Which gas?

A) OxygenB) Carbon dioxideC) NitrogenD) Hydrogen

✅ A) Oxygen.

3. The waste made

What two things are made in aerobic respiration?

A) Glucose + oxygenB) Carbon dioxide + waterC) Salt + sugarD) Oil + gas

✅ B) Carbon dioxide + water.

4. Today's lead-in

In an equation, the things that go IN are on the…

A) LeftB) Right

✅ A) Left. The "ingredients" go on the left of the arrow.

1. Word equation

Which is the correct word equation for aerobic respiration?

A) Glucose + Oxygen → Carbon Dioxide + WaterB) Glucose + Carbon Dioxide → Oxygen + WaterC) Oxygen + Water → Glucose + Carbon DioxideD) Glucose → Carbon Dioxide + Oxygen

✅ A) Glucose + Oxygen → Carbon Dioxide + Water.

2. Not the same as breathing

Respiration is…

A) moving air in and out of the lungsB) a reaction in cells that releases energyC) exactly the same as breathingD) something only plants do

✅ B) A chemical reaction in cells that releases energy.

3. Why so many mitochondria?

Muscle cells have lots of mitochondria because they…

A) store fatB) need lots of energy (ATP)C) make oxygenD) need colour

✅ B) They need lots of energy (ATP) to contract.

4. Today's lead-in

The chemical formula for glucose is…

A) CO₂B) H₂OC) C₆H₁₂O₆D) O₂

✅ C) C₆H₁₂O₆.

1. Releases, not makes

We say respiration releases energy (not makes it) because…

A) energy is already stored in glucose and is let outB) cells make energy from nothingC) energy comes from the airD) energy is made in the lungs

✅ A) The energy is already stored in glucose — respiration releases it.

2. The big number

In 6O₂, what does the big 6 in front mean?

A) six molecules of oxygenB) six gramsC) six degreesD) six cells

✅ A) Six molecules of oxygen.

3. Write it (scaffolded)

Fill the gaps to make the word equation:

____ + ____ → ____ + ____ (+ ATP)

Word bank: glucose · oxygen · carbon dioxide · water

✅ Glucose + Oxygen → Carbon Dioxide + Water (+ ATP)

4. Why oxygen helps (scaffolded)

Finish the sentence:

"Oxygen lets glucose break down ________, so it releases ________ energy."

Choose from: completely / a little • lots of / hardly any

✅ Oxygen lets glucose break down completely, so it releases lots of energy.

Starter

🕵️ Starter: Equation Detective

Your mission: Four equations are in the line-up. Only ONE is the real aerobic respiration equation — the other three are imposters. Decide in your book first, then tap a suspect to investigate. No calling out!

Suspect AGlucose + Water → Carbon Dioxide + Oxygen + ATPtap to investigate ▸

Suspect BOxygen + Carbon Dioxide → Glucose + Water + ATPtap to investigate ▸

Suspect CGlucose + Oxygen → Carbon Dioxide + Water + ATPtap to investigate ▸

Suspect DGlucose → Oxygen + Carbon Dioxide + ATPtap to investigate ▸

🧠 Detective's hint: Ask two things — what does respiration need (goes LEFT)? What does it make (goes RIGHT)?

Aspire: Be the lead detective — for each imposter, give its "alibi": say exactly what's wrong with it.

I Do

I Do: The Aerobic Respiration Equations (Spec 2.37)

Key Idea: Aerobic respiration has two equations that mean the same thing — a word equation and a symbol equation.

1 · The Word Equation

Glucose + Oxygen → Carbon Dioxide + Water

Reactants (LEFT): glucose and oxygen go in.

Products (RIGHT): carbon dioxide and water come out (plus ATP, the energy).

2 · The Symbol Equation

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

The same equation in chemical "code". The big 6 means six molecules. C₆H₁₂O₆ is the formula for glucose.

Copy it exactly: keep the small subscript numbers and the big 6s in front of O₂, CO₂ and H₂O.

🧠 Memory Trick: "Giant Octopus Caught Water" → Glucose + Oxygen → Carbon dioxide + Water. Reactants first, products after.

Watch it flow: reactants IN → products OUT

Reactants — go IN (left)

🍬 Glucose (C₆H₁₂O₆)

🫁 Oxygen (6O₂)

→

Mitochondria

→

Products — come OUT (right)

💨 Carbon dioxide (6CO₂)

💧 Water (6H₂O)

🔋 ATP (energy!)

Reactants go IN → broken down in the mitochondria → products come OUT.

Why so much energy (ATP)?

Because there is oxygen, glucose is broken down completely into CO₂ and water. Almost all the energy stored in glucose is released — so aerobic respiration gives a large amount of ATP.

Aspire: Why does aerobic respiration release so much ATP?

Don't write: C6H12O6 + O2 → CO2 + H2O (the 6s are missing)

Write: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (with the 6s!)

The big 6s in front of O₂, CO₂ and H₂O are part of the correct equation — copy them every time.

Talk to your partner: What are the two reactants and the two products of aerobic respiration? Be ready to build the equation next.

📺 Observe

Observe: See Aerobic Respiration Happen

Watch & check: You've met both equations — now see them in action. Watch the clip, spot the three things below, then finish the sentences. This is exactly what you'll build on your own next — unaided.

Open on YouTube ↗ Backup clips ↗

If the video is blocked on the network, use the links above — or revisit the Watch it flow animation on the previous slide.

👀 While you watch, spot 3 things:

What goes IN — the two reactants
What comes OUT — the two products (+ ATP)
Where in the cell it happens

Listen carefully: a clip may just say "energy" — in your exam, write ATP. And keep the big 6s in the symbol equation.

✍️ Now finish these — say it out loud first, then jot it down:

The two reactants are ____________ and ____________.
The two products are ____________ and ____________.

Aerobic respiration happens in the ____________.
It releases a large / small amount of ATP because oxygen breaks glucose down ____________.

Reactants: glucose & oxygen. Products: carbon dioxide & water (+ ATP). It happens in the mitochondria. It releases a large amount of ATP because glucose is broken down completely.

Ready check: Cover the screen — can you say the word equation out loud, in the right order? If yes, you're ready to build it yourself in the next task.

We Do

We Do: Build Both Aerobic Equations

Instructions: Drag each tile into the right gap to build the word equation and the symbol equation. Reactants go LEFT, products go RIGHT. (Works by touch or mouse.)

Tiles placed: 0/8

Tile bank — drag each into the right place:

Carbon Dioxide

6O₂

Glucose

6H₂O

Oxygen

C₆H₁₂O₆

Water

6CO₂

1 · Word Equation

Reactants (IN)

fuel
(sugar)

gas
breathed in

→

Products (OUT)

waste
gas

liquid

2 · Symbol Equation

Reactants (IN)

glucose
formula

oxygen
×6

→

Products (OUT)

CO₂
×6

water
×6

🧡 Tip: The word and symbol equations say the same thing — just different "languages". The matching 6s belong in front of O₂, CO₂ and H₂O.

Word: Glucose + Oxygen → Carbon Dioxide + Water. Symbol: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O. The order on each side matches!

Independent Work

Independent Work – Aerobic Respiration Equations

Instructions: Complete your printed worksheet at your level. You may use the equations from the starter and the knowledge organiser.

Independent Work Timer

08:00

Foundation (Grades U–1)

Multiple choice, then fill the gaps in both equations using a word bank.

Middle (Grades 2–3)

Multiple choice, then write both equations (with a word bank to lean on).

Higher (Grades 3–5)

Write both equations and a short scaffolded 4-mark exam question.

📋 Scaffolding

Every pack includes both equations, a word bank, and sentence starters. Use them whenever you need them — that's what they're for.

🏆 Success Criteria

Foundation (U–1): I can complete the word equation, name the formula for glucose, and say which side reactants and products go.

Middle (2–3): I can write the word equation and copy the symbol equation, including the 6s.

Higher (3–5): I can write both equations and explain what the 6s mean and why aerobic respiration releases so much ATP.

Exit Ticket

Exit Ticket – Aerobic Respiration Equations

Knowledge check: Tap your answer to each question — you'll get instant feedback and a score at the end. Books closed, no notes!

Score: 0/6

🖨️ Print written exit ticket:

Name: ________________________ Class: __________ Date: ____________

🎯 Learning Objective (2.37): Know the word equation and the symbol equation for aerobic respiration, and what the big 6s mean.

🏆 Success Criteria — tick at the END of the lesson:

☐ I can pick out the word equation and name the reactants and products.

☐ I can write the word equation and copy the symbol equation (with the 6s).

☐ I can explain what the big 6s mean.

Knowledge Organiser – Lesson 4: Aerobic Respiration Equations

Item	Details
Word equation	Glucose + Oxygen → Carbon Dioxide + Water (+ ATP)
Symbol equation	C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
Reactants	Go INTO the reaction — on the LEFT of the arrow (glucose + oxygen).
Products	Come OUT of the reaction — on the RIGHT (carbon dioxide + water).
The 6s	A big number in front means how many molecules. 6O₂ = six oxygen molecules.
C₆H₁₂O₆	The chemical formula for glucose.
Why so much ATP?	Oxygen breaks glucose down completely, releasing almost all the stored energy.
Where?	Mitochondria — the "powerhouse of the cell".

✍️ Sentence starters you can use: The two reactants are ______ and ______. · The two products are ______ and ______. · The big 6s mean ______ (how many molecules).

🧠 Self-quiz: COVER the equations → WRITE from memory → CHECK → fix gaps. Do it twice.

⚠️ Common mark-losers: dropping the 6 in the symbol equation · writing energy is "made" (it is released) · putting oxygen on the right · forgetting glucose is C₆H₁₂O₆.

🎵 Memory hook: "Giant Octopus Caught Water" = Glucose + Oxygen → Carbon dioxide + Water.

Arrival Task — The Fab 4

📌 Use this to help you:

• Word equation: Glucose + Oxygen → Carbon Dioxide + Water (+ ATP)

• Reactants go IN (left of arrow); products come OUT (right).

• Energy is released (let out) from glucose — not made. The energy is ATP.

• The big 6s (in 6O₂, 6CO₂, 6H₂O) mean six molecules.

Foundation

1) Which gas does aerobic respiration need?
A) Oxygen B) Nitrogen C) Carbon dioxide

2) What does ATP give a cell?
A) Energy B) Water C) A colour

3) Reactants go on which side of the arrow?
A) Left B) Right

4) Use the diagram. Write the TWO things that go IN:

Middle

1) The word equation is:
A) Glucose + Oxygen → Carbon Dioxide + Water
B) Glucose + Carbon Dioxide → Oxygen + Water
C) Oxygen + Water → Glucose + Carbon Dioxide

2) In 6O₂ the big 6 means:
A) six molecules B) six grams C) six degrees

3) Which gas does respiration need?
A) Oxygen B) Carbon dioxide C) Nitrogen

4) Use the diagram. Write the TWO products (come OUT):

Higher

1) The big 6s (in 6O₂, 6CO₂, 6H₂O) tell us:
A) how many molecules B) the temperature C) the mass in grams

2) The reactants of aerobic respiration are:
A) glucose + oxygen B) carbon dioxide + water C) glucose + water

3) We say respiration releases energy because:
A) it is stored in glucose and let out B) cells make it from nothing C) it comes from the air

4) Use the diagram. Write the word equation:

🕵️ Starter: Equation Detective

Four suspects are in the line-up. Only ONE is the real aerobic respiration equation — the other three are imposters. Circle the real one, then give each imposter its "alibi" (what's wrong).

Real?	Suspect equation
	A) Glucose + Water → Carbon Dioxide + Oxygen + ATP
	B) Oxygen + Carbon Dioxide → Glucose + Water + ATP
	C) Glucose + Oxygen → Carbon Dioxide + Water + ATP
	D) Glucose → Oxygen + Carbon Dioxide + ATP

The real equation is: ________

The alibis – what's wrong with each imposter?

A's alibi:

B's alibi:

D's alibi:

Scaffolding Sheet – Foundation (Grades U–2)

Both Equations

Word: Glucose + Oxygen → Carbon Dioxide + Water

Symbol: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Sentence Starters

The reactants of aerobic respiration are ________ and ________.

The products of aerobic respiration are ________ and ________.

The chemical formula for glucose is ________.

📝 Word Bank (Foundation)

Use these words: glucose · oxygen · carbon dioxide · water · reactants · products · left · right · mitochondria

⭐ Exam frame

(a) The two reactants are ________ and ________.

(b) The two products are ________ and ________.

Scaffolding Sheet – Middle (Grades 1–3)

Equations

Word: Glucose + Oxygen → Carbon Dioxide + Water

Symbol: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Key Words

Reactants	Left side of the arrow (go IN).
Products	Right side of the arrow (come OUT).
The 6s	Six molecules — copy them in front of O₂, CO₂, H₂O.
C₆H₁₂O₆	Formula for glucose.

Scaffolding Sheet – Higher (Grades 2–4)

What the symbol equation means

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Part	What it means
C₆H₁₂O₆	one glucose molecule (the fuel)
6O₂	six oxygen molecules (the gas needed)
6CO₂	six carbon dioxide molecules (waste gas)
6H₂O	six water molecules (waste liquid)

Sentence starters

The big 6s mean ________.

Aerobic respiration releases lots of ATP because oxygen lets glucose ________.

Key Terms

reactants · products · molecule · C₆H₁₂O₆ · mitochondria · complete breakdown · ATP

Independent Work – Foundation (Grades U–2)

📝 Word bank: glucose · oxygen · carbon dioxide · water | Use your scaffold sheet to help you.

Part A: Multiple Choice (circle the answer)

1) Which gas does aerobic respiration need? A) Oxygen B) Nitrogen C) Carbon dioxide

2) The chemical formula for glucose is: A) C₆H₁₂O₆ B) H₂O C) O₂

3) Reactants go on which side of the arrow? A) Left (go in) B) Right (come out)

4) Which TWO things are made (the products)? A) Carbon dioxide + water B) Glucose + oxygen C) Salt + sugar

Part B: Copy and Fill (use the word bank)

5) Copy the word equation neatly below:

Glucose + Oxygen → Carbon Dioxide + Water

6) Fill the two gaps: Glucose + __________ → Carbon Dioxide + __________

7) Fill in the missing 6s: C₆H₁₂O₆ + ____ O₂ → ____ CO₂ + ____ H₂O

Part C: Short Answer — finish the sentences

8) The two reactants are __________ and __________.

The two products are __________ and __________.

Part D: Exam Question [2 marks]

9) Write the word equation for aerobic respiration. [2] (use the word bank)

Starter: __________ + __________ → __________ + __________

Independent Work – Middle (Grades 1–3)

📝 Word bank: glucose · oxygen · carbon dioxide · water | Use your scaffold sheet to help you.

Part A: Multiple Choice (circle the answer)

1) The word equation for aerobic respiration is: A) Glucose + Oxygen → Carbon Dioxide + Water B) Glucose + Carbon Dioxide → Oxygen + Water C) Oxygen + Water → Glucose + Carbon Dioxide

2) In 6O₂, the big 6 in front means: A) six molecules of oxygen B) six grams C) six degrees

3) Reactants go on which side of the arrow? A) Left (go in) B) Right (come out)

Part B: Short Answer (use the word bank)

4) Fill the gaps: Glucose + __________ → __________ + Water

5) Copy the symbol equation (with the 6s): C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

6) Finish the sentences:

The reactants are __________ and __________.

The products are __________ and __________.

Part C: Short Explanation — use the starters

7) What do "reactants" and "products" mean?

Reactants are the things that go __________ (in / out), on the __________ of the arrow.

Products are the things that come __________, on the __________ of the arrow.

Part D: Exam Question [3 marks]

8) Write the word equation, and say what the big 6s mean. [3]

Frame: "The word equation is __________. The big 6s mean __________ (how many molecules)."

Independent Work – Higher (Grades 2–4)

📝 Word bank: glucose · oxygen · carbon dioxide · water · molecules | Use your scaffold sheet to help you.

Part A: Multiple Choice (circle the answer)

1) In the symbol equation, the big 6s tell us: A) how many molecules B) the temperature C) the mass in grams

2) The reactants of aerobic respiration are: A) glucose + oxygen B) carbon dioxide + water C) glucose + water

Part B: Short Answer

3) Write the word equation for aerobic respiration.

4) Write the symbol equation for aerobic respiration (include the 6s).

5) Explain what the big 6s mean. Starter: "The big 6s mean __________."

Part C: Long Answer — use the frame

6) Explain how the word equation and the symbol equation show the same reaction. Use the words reactants, products and molecules.

Frame: "Both equations have the same reactants (__________ and __________) and the same products (__________ and __________). The symbol equation uses __________ instead of words."

Part D: Exam Question [4 marks] — use the frame

7) Write the word and symbol equations, and explain why you must include the 6s. [4]

Frame: "The word equation is __________. The symbol equation is __________. You must include the 6s because they show __________."

Exit Ticket – Aerobic Equations (Foundation U–2)

Name: ______________________ Class: __________ Date: __________

Answer from memory — no notes.

1) Complete: Glucose + __________ → Carbon Dioxide + __________

2) What is the chemical formula for glucose?

3) Name the two reactants of aerobic respiration.

4) Name the two products of aerobic respiration.

5) Reactants go on the LEFT or RIGHT of the arrow? Circle: LEFT / RIGHT

6) Which gas is needed for aerobic respiration?

Exit Ticket – Aerobic Equations (Middle 1–3)

Name: ______________________ Class: __________ Date: __________

Answer from memory — no notes.

1) Write the word equation for aerobic respiration.

2) Write the symbol equation for aerobic respiration (don't forget the 6s).

3) What does the big 6 in 6O₂ mean?

4) How many molecules of CO₂ are produced?

5) What goes on the LEFT of the arrow — reactants or products?

6) In which organelle does aerobic respiration happen?

Exit Ticket – Aerobic Equations (Higher 2–4)

Name: ______________________ Class: __________ Date: __________

Answer from memory — no notes.

1) Write the symbol equation for aerobic respiration.

2) What do the big 6s in front of O₂, CO₂ and H₂O tell us?

3) Name the two reactants and the two products.

4) Explain why aerobic respiration releases a lot of ATP. Starter: "Because oxygen lets glucose ______."

5) A student writes C₆H₁₂O₆ + 6O₂ → 6CO₂ + H₂O. The 6 is missing from the water — write it correctly.

6) Explain why the word and symbol equations describe the same reaction.

Lesson 4: Aerobic Respiration

🏆 By the end I will be able to…

Teacher Print Tools – Lesson 4

Before We Start: Respiration & ATP in 60 Seconds

What happens inside a cell

The Fab 4 – Recall to Get You Started

1. Energy

2. The gas needed

3. The waste made

4. Today's lead-in

1. Word equation

2. Not the same as breathing

3. Why so many mitochondria?

4. Today's lead-in

1. Releases, not makes

2. The big number

3. Write it (scaffolded)

4. Why oxygen helps (scaffolded)

🕵️ Starter: Equation Detective

I Do: The Aerobic Respiration Equations (Spec 2.37)

1 · The Word Equation

2 · The Symbol Equation

Watch it flow: reactants IN → products OUT

Why so much energy (ATP)?

Observe: See Aerobic Respiration Happen

We Do: Build Both Aerobic Equations

Independent Work – Aerobic Respiration Equations

Foundation (Grades U–1)

Middle (Grades 2–3)

Higher (Grades 3–5)

📋 Scaffolding

🏆 Success Criteria

Exit Ticket – Aerobic Respiration Equations

Knowledge Organiser – Lesson 4: Aerobic Respiration Equations

Arrival Task — The Fab 4

Foundation

Middle

Higher

🕵️ Starter: Equation Detective

Scaffolding Sheet – Foundation (Grades U–2)

Both Equations

Sentence Starters

Scaffolding Sheet – Middle (Grades 1–3)

Equations

Key Words

Scaffolding Sheet – Higher (Grades 2–4)

What the symbol equation means

Sentence starters

Key Terms

Independent Work – Foundation (Grades U–2)

Independent Work – Middle (Grades 1–3)

Independent Work – Higher (Grades 2–4)

Exit Ticket – Aerobic Equations (Foundation U–2)

Exit Ticket – Aerobic Equations (Middle 1–3)

Exit Ticket – Aerobic Equations (Higher 2–4)

🎓 TA Focus

🎯 Cold Call

📺 Aerobic Respiration Equations

🏆 Class Progress Board

🎉 Lesson Complete!