Nitrogen: The Quiet Giant
The gas that fills most of the air.
What this lesson covers
Why it matters
Take a deep breath. Nearly four out of every five parts of that air is nitrogen — a calm, quiet gas that hardly reacts at all, yet fills most of the sky above us.
Predict first
About how much of the air is nitrogen?
Nitrogen makes up about 78% of the air — by far its largest part. Oxygen is about 21%, and the rest is a small mix of other gases.
- About 78% — most of the air — correct
- About 21% — the same as oxygen
- Almost none of it
- Exactly half of it
What you do
Decide whether each statement about nitrogen is TRUE or FALSE, and drag it into the right bin.
Check yourself
Why is it useful that most of the air is unreactive nitrogen?
If the air were pure oxygen, fires would rage out of control. Nitrogen mixes in and dilutes the oxygen, so burning stays gentle and controlled.
What is nitrogen fixation?
Nitrogen gas is too unreactive for plants to use directly. Bacteria (and lightning) fix it — turning it into nitrates in the soil that plants can absorb to grow.
Which statement about nitrogen is TRUE?
Nitrogen is used to make fertilisers that help plants grow. It does not support burning and does not affect lime water.
- It dilutes the oxygen so things do not burn too fast or too violently — correct
- It makes fires burn much more fiercely
- It turns the air into a liquid
- It stops us from breathing
- Changing unreactive nitrogen (N₂) into nitrates that plants can use — correct
- Turning nitrogen into oxygen
- Freezing nitrogen into ice
- Burning nitrogen as a fuel
- It is used to make fertilisers for crops — correct
- It relights a glowing splint like oxygen
- It turns lime water milky
- It is the smallest part of the air