Vital Capacity
Somewhere between three and five litres of air moves through your lungs when you take the biggest breath you possibly can. You have been doing this your whole life — but you have never measured it.
9-12 yrs
Easy
30
min
Stage 3
Mission Briefing.
Designed by Darin Carr (BSc, DipEd)
NESA Accredited Teacher Chemistry & Physics Specialist
Creator of the LAB™ Learning System
Essy
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Vital Capacity
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NESA Accredited Teacher
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High school chemistry & physics specialist 30+ years
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The Crazy Scientist in primary schools — 15 years
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International conference presenter on science education
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Creator of the LAB™ Learning System
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Curriculum aligned: NSW Science & Technology K–6 (2024)
A picture is worth a thousand words — check this out and see if you can spot the science hiding in plain sight.
Mission Equipment
A large clear plastic bottle — 2 litre minimum, 3 litre ideal
A large bowl or container deep enough to hold the bottle upside down
Water
A flexible plastic tube or long straw (about 50 cm)
A permanent marker
A ruler
A measuring jug
Let’s Investigate
1
Prepare measuring bottle
Using a ruler and permanent marker, draw horizontal lines on the outside of your plastic bottle at 100 ml intervals from the bottom up.
3
Make predictions
Before anyone measures — make class predictions.
Look around the room and predict: who do you think will have the largest vital capacity? The smallest?
2
Set up Apparatus
Fill the marked bottle completely to the top with water and put the cap on.
Fill your bowl or container with water to about 10 cm depth.
Carefully flip the full bottle upside down and lower its mouth into the water in the bowl — then, keeping the mouth underwater, remove the cap.
4
Measure capacity
Stand next to the apparatus. Take the deepest breath you possibly can — fill your lungs completely.
Place your mouth on the tube and breathe out as hard and as fully as you can until there is genuinely nothing left to give.
Mark the new water level on the bottle. This is your vital capacity — read it from the markings.
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You breathe roughly 20,000 times a day without thinking about it. But when you really push — when you sprint, swim hard, or play a wind instrument — your lungs are working at a completely different level.
Think of someone you know who is a really good swimmer, a runner, or plays a brass or woodwind instrument.
Do you think their lungs work differently from someone who does not train? In what way?
You have measured your vital capacity and built the class dot plot.
Think back to your prediction — was your actual vital capacity higher or lower than you expected? By how much? What does that tell you about how well people know their own bodies?
What you measured today has a specific scientific name: vital capacity. Why do you think doctors and physiologists use this measurement? What would a lower-than-average vital capacity in an adult tell a doctor?
Vital capacity is a real clinical measurement — doctors, athletes, and researchers use it to assess lung health, fitness, and performance.
Wind instrument players — trumpet, clarinet, saxophone, didgeridoo — consistently show above-average vital capacity. Is that because people with larger lungs choose these instruments, or because playing the instrument trains the lungs? How would you design an experiment to find out which explanation is correct?
"Want the full teacher guide? The Crazy Scientist Lab includes classroom delivery tips, how to manage the WOW moment, differentiation for Stage 2 & 3, — ready to teach tomorrow."
Think Like a Scientist
Scientists don't just do ONE experiment; they change one part of the experiment (independent variable) and then see how it affects another part of the experiment
(dependent variable)
Change ONE variable and test again.
Does physical activity immediately before measuring change your vital capacity result?
Does physical activity immediately before measuring change your vital capacity result?
🧪 Try it! Change ONE thing and test again. What did you discover?
Dr Puddledrip’s Science Tip
Want to go deeper? Tap a section below to explore. ▼
The Science Behind It
Vital capacity is defined as the maximum volume of air that can be exhaled following a maximum inhalation. It is one of several lung volumes that physiologists measure to understand how the respiratory system works.
The four primary lung volumes are: tidal volume — the air moved in a normal, relaxed breath (approximately 0.5 litres); inspiratory reserve volume — the extra air you can inhale beyond a normal breath (approximately 3 litres); expiratory reserve volume — the extra air you can push out beyond a normal exhale (approximately 1.1 litres); and residual volume — the air that permanently remains in the lungs after maximum exhalation (approximately 1.2 litres).
Vital capacity = tidal volume + inspiratory reserve + expiratory reserve. It is the total range of air you can voluntarily move. It does not include residual volume, because residual volume cannot be controlled — it is set by the elastic properties of the lung tissue itself. If the lungs fully collapsed with every exhale, reinflating them would require enormous muscular effort and would damage the delicate alveoli. The residual volume keeps them slightly inflated at all times.
Your lungs contain approximately 600 million alveoli — tiny air sacs with walls only one cell thick. The total surface area of all these alveoli is approximately 70 square metres — the size of a singles tennis court. This enormous surface area allows rapid gas exchange: oxygen diffuses from the air in the alveoli into the blood, and carbon dioxide diffuses in the opposite direction, in the time it takes for a red blood cell to pass through a capillary.
Vital capacity is influenced by height (taller chest cavity), age (peaks around age 20–25), biological sex (males average slightly more due to larger chest size), aerobic fitness (respiratory muscles strengthen with training), and specific training such as swimming or wind instrument playing. Doctors use spirometry — a precise clinical measurement of lung volumes — to diagnose conditions including asthma, COPD, and pulmonary fibrosis, all of which reduce vital capacity in characteristic ways.
Extension: G&T Years 5 & 6
Vocabulary
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