Aut1·W4 (Use) — Apply diffusion to gas exchange; evidence with the limewater CO2 test.
Edexcel GCSE Biology 1BI0 Foundation · Paper 1 · Topic 1Pearson Edexcel GCSE (9–1) Biology 1BI0 (Foundation, grades 1–5); GCSE Combined Science 1SC0 F where appropriate; AQA UAS science units
🎯 Learning Objective: I can apply diffusion to gas exchange in the alveoli, and use the limewater test as evidence that the body makes carbon dioxide.
✅ Success Criteria
I can name the three adaptations of an alveolus and link each to diffusion.
I can predict and record the limewater result for breathed-out air.
I can use the result to explain what gas exchange removes from the body.
🔗 Assessment link: AQA UAS: 'Cells and transport'; 'Carrying out a practical investigation'.
LAUNCH · one 40-minute session. Title orientation is untimed; keep the full 15-minute independent task.
Teacher timing and core practice
40-minute session: Arrival 3; overview 1; I Do 1 4; We Do 1 4; I Do 2 3; We Do 2 4; independent work 15; feedback and next step 3; exit 3. Title orientation is untimed. The optional two-minute evidence check sits inside independent time. Keep extra practice available; use the core question, a contrasting example and a recheck before extending.
From the word bank, name the gas that diffuses INTO the blood at the alveolus.
▲ Standard
Name one adaptation of an alveolus and say how it helps diffusion.
★ Stretch
Name two alveolus adaptations and link each one to a factor that speeds up diffusion.
🗺️ Today at a Glance
Three things we do today
1.
Three adaptations
2.
Predict the limewater
3.
Explain the result
👩🏫 I Do · watch me think
Watch me set the test up — then you run it
🧠 Watch me think: The adult has prepared two labelled limewater comparisons using the centre-approved method. We predict a difference between room air and breathed-out air before we observe it. We compare the same observation window and controlled gas delivery. I show you what is actually observed, not what the prediction says must happen. You may observe, time, record or interpret; the operator and data source go on your record.
At the alveolus, ● O2 diffuses in and ○ CO2 diffuses out — helped by a large surface area, a one-cell-thick wall and a good blood supply. Cloudy limewater is the evidence the body makes CO2.
📖 Key definitions
alveolus — A tiny air sac in the lung where gas exchange happens.
gas exchange — Oxygen diffusing into the blood and carbon dioxide diffusing out.
limewater — A clear liquid that turns cloudy/milky when carbon dioxide bubbles through it.
adaptation — A feature that makes a structure better at its job.
❌ Common mistake: The lungs make oxygen. ✅ Actually: They do not make it. Oxygen diffuses IN from the air; the lungs are the exchange surface.
🤝 We Do · together
Predict, then check
Say your prediction before you tap.Found 0/5
Which gas diffuses INTO the blood?
Which gas diffuses OUT into the alveolus?
Breathed-out air through limewater
Room air drawn through limewater
Wall one cell thick
👩🏫 I Do 2 · the evidence loop
Evidence loop
🧠 Watch me think: You close the loop, not me. Say and write the conclusion as a frame: 'The limewater went cloudy ____ with breathed-out air, so breathed-out air has ____ carbon dioxide, because respiration in my cells makes it and gas exchange removes it.' Result, then reason. A wrong prediction is fine — we record what happened, not what we hoped.
Assessor witness · what the adult is watching for
Linked three alveolus adaptations to diffusion.
Predicted and recorded the comparison; role identified as operator, observer or supplied-data analyst.
Used the observed or identified supplied comparison to explain the carbon-dioxide evidence and a limit.
📸 Capture: Keep the pupil’s comparison record with actual observations, the operator/data source and their conclusion. Record an endpoint time only if it was measured.
🤝 We Do 2 · sort, then write
Match the adaptation to the reason
Sort, don’t guess. Match each card to the right answer.Matched 0/6
Large surface area
Wall one cell thick
Good blood supply
Moist lining
Cloudy limewater
The lungs make oxygen
More room for gases to cross — faster diffusion
Short diffusion distance — faster diffusion
Keeps the concentration gradient steep
Gases dissolve before they diffuse
Carbon dioxide is present — the positive result
NOT TRUE — oxygen diffuses in from the air
✏️ Independent Work
Your turn — pick your tier
Prepared comparison · 15-minute work block.
Your adult prepares and checks the centre-approved apparatus before class. Use the adult-operated comparison, an approved supervised pupil role, or a clearly identified record of a completed comparison. Nobody has to provide a breath sample or exercise.
Spend 2 minutes checking the two labels and prediction; up to 5 observing/timing the prepared comparison; 3 recording what actually happened; 2 checking your evidence; 3 explaining the result and linking an alveolus adaptation to diffusion. Your adult sets the same observation window and comparable gas delivery for both tubes. If a change is not seen, record “not seen within the observation window”; do not invent a time or treat that alone as proof that carbon dioxide is absent. Stop at the planned endpoint and continue with an identified recorded comparison if needed.
Write “pupil measurement”, “observed adult demonstration” or “supplied record”. Use only the agreed apparatus and safety controls; no sucking liquid or shared mouthpieces. A quiet observer, timer, recorder or interpreter has a full Science role.
15 minutes. Choose the tier your adult rings for you.
Use the task time to work, check and improve: reserve up to two of these 15 minutes for an evidence check with your adult or a partner, then act on one useful point. Point, say, sign, demonstrate, write or use an agreed scribe. Manual pause stays available.
15:00
◆ Supported
Choose an approved role in the prepared limewater comparison, or use the identified supplied record. Fill the results table with actual observations and complete the conclusion from the word bank; name your role and the data source.
▲ Standard
Take an approved role in the prepared comparison, or analyse the identified supplied record. Record actual observations and any measured times, label the three alveolus adaptations, and write a conclusion supported by the record.
★ Stretch
Take an approved role in the prepared comparison, or analyse its identified record. Compare observations and measured times only where controls permit; name a method limit, then explain each alveolus adaptation using diffusion factors.
🔁 Lundy Loop
Where what you say changes something
This is where your voice changes what happens next.
🛡 Space
You never have to be the one who breathes out or exercises. Timing and recording the limewater is the assessed job, and it is yours if you want it.
🗣 Voice
If your result disagrees with my prediction, say so — we look at the method, then the number. The prediction can be wrong; that is data.
👂 Audience
Your results table is Topic 1 evidence and goes into your folder for the W7 review.
⚙ Influence
Staff set the approved safety method. Pupils can choose a workable role and suggest an evidence check; the adult explains what change can be made.
🎫 Exit Ticket
Before you go
◆ Supported
What colour does limewater go when carbon dioxide is present?
cloudy / milky
▲ Standard
Name one alveolus adaptation and say how it speeds up diffusion.
e.g. wall one cell thick — short diffusion distance, so faster diffusion
★ Stretch
Explain why breathed-out air turns limewater cloudy faster than room air.
Breathed-out air has more carbon dioxide from respiration, so more CO2 passes through the limewater and turns it cloudy faster.
Slide 1/10
🏅📸✍️
Use: Diffusion in the Lungs — Testing Breath — banked!
LAUNCH Science · Week 4 ✅
✓ I can name the three adaptations of an alveolus and link each to diffusion.✓ I can predict and record the limewater result for breathed-out air.✓ I can use the result to explain what gas exchange removes from the body.
⏸ MID-POINT PEER CHECK
Pens down — quick partner check!
📣 Show your partner where you’re up to. Check together against today’s success: I can name the three adaptations of an alveolus and link each to diffusion. and I can predict and record the limewater result for breathed-out air.. If something’s missing, help them add it — kindly.
Optional check: use up to two minutes of the independent-work allocation. Manual pause is available if you need more time.
Knowledge Organiser — Use: Diffusion in the Lungs — Testing Breath
LAUNCH · Edexcel GCSE Biology 1BI0 Foundation · Paper 1 · Topic 1 · Week 4
Key word
What it means
alveolus
A tiny air sac in the lung where gas exchange happens.
gas exchange
Oxygen diffusing into the blood and carbon dioxide diffusing out.
limewater
A clear liquid that turns cloudy/milky when carbon dioxide bubbles through it.
adaptation
A feature that makes a structure better at its job.
capillary
The tiniest blood vessel, one cell thick, next to the alveolus.
Key facts
Oxygen diffuses from the alveolus (high O2) into the blood (low O2). Carbon dioxide diffuses the other way.
Three alveolus adaptations: large surface area, wall one cell thick (short distance), good blood supply (keeps the gradient steep).
Limewater turns from clear to cloudy when carbon dioxide passes through it.
Breathed-out air turns limewater cloudy faster than breathed-in air — it has more carbon dioxide.
The extra carbon dioxide comes from respiration in the body's cells and is removed by gas exchange.
Success criteria
I can name the three adaptations of an alveolus and link each to diffusion.
I can predict and record the limewater result for breathed-out air.
I can use the result to explain what gas exchange removes from the body.
Session plan: 40-minute session: Arrival 3; overview 1; I Do 1 4; We Do 1 4; I Do 2 3; We Do 2 4; independent work 15; feedback and next step 3; exit 3. Title orientation is untimed. The optional two-minute evidence check sits inside independent time. Keep extra practice available; use the core question, a contrasting example and a recheck before extending.
Prepared comparison · 15-minute work block.
Your adult prepares and checks the centre-approved apparatus before class. Use the adult-operated comparison, an approved supervised pupil role, or a clearly identified record of a completed comparison. Nobody has to provide a breath sample or exercise.
Spend 2 minutes checking the two labels and prediction; up to 5 observing/timing the prepared comparison; 3 recording what actually happened; 2 checking your evidence; 3 explaining the result and linking an alveolus adaptation to diffusion. Your adult sets the same observation window and comparable gas delivery for both tubes. If a change is not seen, record “not seen within the observation window”; do not invent a time or treat that alone as proof that carbon dioxide is absent. Stop at the planned endpoint and continue with an identified recorded comparison if needed.
Write “pupil measurement”, “observed adult demonstration” or “supplied record”. Use only the agreed apparatus and safety controls; no sucking liquid or shared mouthpieces. A quiet observer, timer, recorder or interpreter has a full Science role.
Comparison record
Source/date: __________. My role: __________. Tube labels: __________ / __________. Observation window: __________. Actual observations/times: __________ / __________. Controls checked: __________. A missing endpoint is recorded as “not seen within the observation window”, never as a made-up time.
Conclusion: The evidence I used was __________. It supports __________. One limit is __________. The person who operated the apparatus was __________.
Use: Diffusion in the Lungs — Testing Breath
Name: ____________________ Tier ringed by adult: ◆ Supported ▲ Standard ★ Stretch Date:
Learning objective
I can apply diffusion to gas exchange in the alveoli, and use the limewater test as evidence that the body makes carbon dioxide.
Today at a Glance
Three adaptations
Predict the limewater
Explain the result
Arrival task
From the word bank, name the gas that diffuses INTO the blood at the alveolus.
Name one adaptation of an alveolus and say how it helps diffusion.
Name two alveolus adaptations and link each one to a factor that speeds up diffusion.
We Do — Match each card
Large surface area → ______________________________
Wall one cell thick → ______________________________
Good blood supply → ______________________________
Moist lining → ______________________________
Cloudy limewater → ______________________________
The lungs make oxygen → ______________________________
WAGOLL
Example conclusion for a comparison that showed this result, not a record of your observation: breathed-out air turned the limewater cloudy faster than room air under comparable test conditions. That supports more carbon dioxide in the breathed-out sample. Carbon dioxide made by respiration in cells is removed at the alveoli, diffusing from blood into alveolar air down its concentration gradient.
Scaffolding — ◆ Supported
Adult notes — access & sensory Prepare and pre-check the centre-approved comparison before class. No exercise or personal breath contribution is required. Confirm suitable apparatus, exposure controls and the observation window; use an identified recorded comparison if a live endpoint is not feasible. Timing, observing, recording and interpreting are valid Science roles; record which steps the pupil actually performed.
Sentence stems
You close the loop, not me. Say and write the conclusion as a frame: 'The limewater went cloudy ____ with breathed-out air, so breathed-out air has ____ carbon dioxide, because respiration in my cells makes it and gas exchange removes it.' Result, then reason. A wrong prediction is fine — we record what happened, not what we hoped.
Word bank
alveolus, gas exchange, limewater, adaptation, capillary
Scaffolding — ▲ Standard
Sentence stems
You close the loop, not me. Say and write the conclusion as a frame: 'The limewater went cloudy ____ with breathed-out air, so breathed-out air has ____ carbon dioxide, because respiration in my cells makes it and gas exchange removes it.' Result, then reason. A wrong prediction is fine — we record what happened, not what we hoped.
Word bank
alveolus, gas exchange, limewater, adaptation, capillary
Scaffolding — ★ Stretch
Sentence stems
You close the loop, not me. Say and write the conclusion as a frame: 'The limewater went cloudy ____ with breathed-out air, so breathed-out air has ____ carbon dioxide, because respiration in my cells makes it and gas exchange removes it.' Result, then reason. A wrong prediction is fine — we record what happened, not what we hoped.
Word bank
alveolus, gas exchange, limewater, adaptation, capillary
Independent Work — ◆ Supported
Task: Choose an approved role in the prepared limewater comparison, or use the identified supplied record. Fill the results table with actual observations and complete the conclusion from the word bank; name your role and the data source.
Independent Work — ▲ Standard
Task: Take an approved role in the prepared comparison, or analyse the identified supplied record. Record actual observations and any measured times, label the three alveolus adaptations, and write a conclusion supported by the record.
Independent Work — ★ Stretch
Task: Take an approved role in the prepared comparison, or analyse its identified record. Compare observations and measured times only where controls permit; name a method limit, then explain each alveolus adaptation using diffusion factors.
Exit Ticket
Name one alveolus adaptation and say how it speeds up diffusion.
Assessor Witness Statement
Pearson Edexcel GCSE (9–1) Biology 1BI0 (Foundation, grades 1–5); GCSE Combined Science 1SC0 F where appropriate; AQA UAS science units Records what was observed, and at which level of independence.
Pupil
____________________
Lesson
Use: Diffusion in the Lungs — Testing Breath — LAUNCH Science · Week 4
Date
____________________
Observed in this lesson
☐ Linked three alveolus adaptations to diffusion.
☐ Predicted and recorded the comparison; role identified as operator, observer or supplied-data analyst.
☐ Used the observed or identified supplied comparison to explain the carbon-dioxide evidence and a limit.
Assessor comment
Ring the tier the pupil actually worked at
◆ Supported
▲ Standard
★ Stretch
Assessor name ______________ Role ____________ Signature ______________ Date ________
Lundy Loop
Space: You never have to be the one who breathes out or exercises. Timing and recording the limewater is the assessed job, and it is yours if you want it.
Voice: If your result disagrees with my prediction, say so — we look at the method, then the number. The prediction can be wrong; that is data.
Audience: Your results table is Topic 1 evidence and goes into your folder for the W7 review.
Influence: Staff set the approved safety method. Pupils can choose a workable role and suggest an evidence check; the adult explains what change can be made.
Closing the loop: this one ends on paper — your own hand, or your words scribed by an adult. Saying it aloud starts the loop; writing it is what closes it. Pass is always allowed.
What I said, and what it changed:
Use: Diffusion in the Lungs — Testing Breath — Feedback Sheet