Nature's Air Factory
Green leaves turn CO₂ and water into food and oxygen.
What this lesson covers
Why it matters
Every green leaf is a tiny factory. Using sunlight, it swallows carbon dioxide and water and quietly builds sugar for the plant — then breathes out the very oxygen we need to live.
Predict first
A healthy green water plant is left in bright sunlight in a jar of water. Tiny bubbles rise from its leaves. Which gas is in those bubbles?
In sunlight, green plants carry out photosynthesis. They take in carbon dioxide and water and release oxygen — that is the gas bubbling off the leaves.
- Carbon dioxide, which the plant breathes out
- Oxygen, made during photosynthesis — correct
- Water vapour turning into gas
- No gas at all; the bubbles are just air stuck on the leaf
What you do
Run the reaction on the bench: give a green leaf carbon dioxide, water, and sunlight. Watch it combine them to make glucose (food stored in the plant) and release oxygen gas. Notice that sunlight is needed to power the whole process.
Check yourself
What TWO things does a leaf need for photosynthesis to happen?
Photosynthesis is powered by sunlight and is carried out by chlorophyll, the green pigment inside leaves.
What does a green plant PRODUCE during photosynthesis?
The plant makes glucose to use as food and releases oxygen gas into the air.
Why is photosynthesis so important for the air we breathe?
Green plants are the chief source of oxygen. By taking in the carbon dioxide that breathing and burning release, photosynthesis keeps the amounts of oxygen and carbon dioxide in the air balanced.
- Sunlight and chlorophyll (the green colour in leaves) — correct
- Darkness and cold
- Salt and sand
- Rust and smoke
- Glucose (food) and oxygen — correct
- Only carbon dioxide
- Rust and water only
- Smoke and ash
- It is the main source of oxygen and it uses up carbon dioxide, balancing the air — correct
- It removes all the oxygen from the air
- It makes the air poisonous
- It has no effect on the air at all