Air Pollution
Primary 6 · Science and Elementary Technology
Air Pollution
Lesson 1 of 4
14 min
Let's begin
Mutesi walks to school past a busy bus park at seven in the morning. By the time she reaches the school gate her eyes sting and she is coughing.
During the holidays, at her grandmother's home high on a green hill, she can breathe deeply all day. Both places have air. So what is different about it?
Air is not one gas. It is a mixture of gases. In every 100 parts of clean, dry air there are about:
| Gas | How much | One use |
|---|---|---|
| Nitrogen | 78 parts (78%) | Used to make fertilisers that help crops grow. |
| Oxygen | 21 parts (21%) | We need it to breathe, and fires need it to burn (combustion). |
| Argon | almost 1 part | Fills old-style light bulbs so the thin wire inside does not burn away. |
| Carbon dioxide | a tiny amount (0.04%) | Plants use it to make food. It is also used in some fire extinguishers and fizzy drinks, and frozen carbon dioxide ("dry ice") is used for cooling. |
Air also carries some water vapour and a little dust. Check the sums: 78 + 21 + 1 = 100.
Air pollution is the presence of harmful substances in the air, in amounts that can hurt people, animals, plants or buildings. A harmful substance in the air is called a pollutant.
Look for a grey or brown haze over a town, visible smoke, black soot on walls and leaves, and dust settling on surfaces. Feel for stinging eyes, a scratchy throat and coughing. Notice bad smells. But remember: some pollutants, like carbon monoxide, cannot be seen or smelt at all.
Warning
Never burn charcoal in a closed room, not even to keep warm on a cold night. It gives off carbon monoxide, which you cannot see or smell, and it can kill people while they sleep. Cook with the door or window open.
Tip
Remember the recipe for air: 78, 21, about 1, and a pinch.
78 nitrogen, 21 oxygen, about 1 argon, and a pinch of carbon dioxide. Anything harmful added to that recipe is a pollutant.
Try each one first, then tap Show answer to check.
Which gas makes up most of the air, and which gas do we need for breathing?
Answer: Nitrogen makes up most of the air (78%). We breathe to take in oxygen (21%).
Gatete sees black specks on the leaves of the plants beside a busy road. What are they, and where did they come from?
Answer: Soot, a pollutant, most likely from the exhaust smoke of vehicles on the road.
"If I can't smell anything, the air is clean." Is this true?
Answer: No. Carbon monoxide has no smell and no colour, but it is poisonous.
What you learned today
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
Quick check
Match each gas to how much of clean, dry air it makes up.
Tap one on the left, then its partner on the right.
