Air, Wind and Sound

Lessons

Primary 4 · Science and Elementary Technology

Air, Wind and Sound

5 lessons

Lesson 2 of 5

What Air Is Made Of

14 min

Let's begin

Uwase lights a candle and covers it with a glass jar. After a few seconds, the flame gets smaller and goes out. "Did the jar blow it out?" asks her little brother.

No. The candle used up something in the air that fires need. Air is not one thing: it is a mixture of gases.

The gases in air

In every 100 parts of clean, dry air there are about:

Gas	How much	Why it matters
Nitrogen	78 parts	The biggest part of air. Plants need nitrogen to grow; it is used to make fertilisers.
Oxygen	21 parts	People and animals need it to breathe. Fires need it to burn.
Argon	almost 1 part	A gas that does not react with other things.
Carbon dioxide	a tiny amount	Plants take it in to make their food. We breathe it out.

Air also carries water vapour (water as an invisible gas) and tiny specks of dust.

That is why Uwase's candle went out: it used up the oxygen in the jar.

Dangers of the parts of air

Air keeps us alive, but some of its parts can be dangerous.

Oxygen helps fires spread. A fire burns faster when more air reaches it, so never fan a fire near dry grass or houses.
Carbon dioxide builds up in closed rooms. Many people breathing in a small closed room can cause headaches and tiredness. Open the windows to let in fresh air.
Carbon monoxide is a poisonous gas made when charcoal burns without enough air. It has no colour and no smell, and it can kill people while they sleep. Never use a charcoal stove in a closed room.
Dust and smoke in the air make people cough and can harm the lungs.
Too much water vapour in a damp house makes mould grow on walls and clothes.

Warning

Never sleep in a room with a burning charcoal stove, even on a cold night. Keep a window or door open whenever you cook.

Tip

78, 21, almost 1, and a pinch

78 nitrogen, 21 oxygen, almost 1 argon, and a pinch of carbon dioxide. Check: 78 + 21 + 1 = 100.

✦

Try it yourself

Try each one first, then tap Show answer to check.

1

Which gas makes up most of the air?

Show answerHide answer

Answer: Nitrogen (78 parts in every 100).

2

Which gas do we need for breathing, and which gas do plants use to make food?

Show answerHide answer

Answer: We need oxygen; plants use carbon dioxide.

3

The classroom feels stuffy after a long lesson with the windows shut. What should the class do, and why?

Show answerHide answer

Answer: Open the windows to let in fresh air, because carbon dioxide builds up and oxygen is used up when many people breathe in a closed room.

Quick check

Match each gas to how much of it is in 100 parts of air.

Tap one on the left, then its partner on the right.

What you learned today

Air is a mixture: about 78 parts nitrogen, 21 parts oxygen, almost 1 part argon and a little carbon dioxide, plus water vapour and dust.
We need oxygen to breathe and fires need it to burn; plants use carbon dioxide.
Air's parts can be dangerous: fires spread, stuffy rooms, and deadly carbon monoxide from charcoal in closed rooms.

Sources and credits

Air, by Simple English Wikipedia contributors, Simple English Wikipedia, CC BY-SA 4.0, adapted by Ganzaa.
Carbon monoxide, by Simple English Wikipedia contributors, Simple English Wikipedia, CC BY-SA 4.0, adapted by Ganzaa.

The exercises (Try it yourself and the practice questions) are written by Ganzaa.

This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.

1The gases in air

2Dangers of the parts of air

Try it yourself

The gases in air

Dangers of the parts of air