Free lesson with a practice sheet
Air around us
Find out what air is made of, why every living thing needs it, what makes air dirty and how we can keep it clean.
Let us begin
The big idea
You cannot see air, but it is all around you. It fills every empty bottle, every room and every balloon. In this lesson you will learn what air is made of, why we need it and how to keep it clean.
Air is a mixture of gases. About 78 parts in 100 are nitrogen, about 21 parts are oxygen, and the last 1 part is a mix of other gases such as carbon dioxide and argon. Air also carries water vapour and tiny bits of dust.
Air takes up space and has weight. Press an empty bottle under water and you will see bubbles escaping: that is the air that was inside. Moving air is called wind. Wind turns windmills, dries clothes and carries seeds and clouds.
All living things need oxygen from the air to stay alive. We breathe in air through our nose, our lungs take the oxygen, and we breathe out carbon dioxide. Plants use carbon dioxide and sunlight to make their food and give out oxygen, so plants help to keep the air fresh.
Smoke from vehicles, factories, burning garbage and crackers puts harmful gases and dust into the air. This is called air pollution. Polluted air makes people cough, hurts the lungs and makes it hard to see far away.
We can keep air clean by planting trees, walking or cycling for short trips, sharing vehicles, not burning garbage or leaves, and keeping our kitchens well ventilated.
Worked examples
See how it works
Air is inside an empty glass
Push an upside-down glass straight down into a bucket of water. The water does not fill the glass. The air inside has taken up the space and pushes the water away. Tilt the glass and bubbles of air rush out.
Why a candle needs air
An adult should light the candle and do this demonstration; never light a candle yourself. A burning candle covered with a glass goes out after a few seconds. Burning uses up the oxygen inside the glass. When the oxygen is gone, the flame cannot keep burning.
A dusty window sill
Wipe a window sill with a wet white cloth. The cloth turns grey. The grey dirt is dust that the air carried in. Near busy roads the cloth gets dirtier faster, because vehicle smoke adds more dust to the air.
Try it at home
Catch the dust in the air
You will need
- Two small pieces of white paper
- A little cooking oil or petroleum jelly
- A pencil
- A spot indoors and a spot near a window or balcony
What to do
Rub a thin layer of oil or jelly on one side of each paper.
Place one paper on a shelf inside a room and the other near an open window or on a balcony, oily side up.
Leave them for a whole day. Do not touch the oily side.
Compare the two papers. Which one caught more dust? Write down what you see.
Think about where that dust came from: roads, construction, cooking smoke or dry soil.
Ask an adult before placing anything on a balcony or window ledge so that it cannot fall.
Practice sheet
Check what you learned
Practice sheet: Air around us (Classes 3-5, Science)
- Which gas makes up the biggest part of the air?
- About how many parts in 100 of the air is oxygen?
- Which gas do we breathe out?
- What is moving air called?
- Name two things that cause air pollution.
- What happens to a candle flame when you cover it with a glass? Why?
- How do plants help keep the air clean?
- Why does a bottle look empty but is not really empty?
- Give two ways to reduce air pollution.
- Why do cloths on a window sill near a busy road get dirty faster?
Answer key
Answers: Air around us
- Nitrogen (about 78 parts in 100).
- About 21 parts in 100.
- Carbon dioxide.
- Wind.
- Any two: smoke from vehicles, factories, burning garbage or leaves, crackers.
- It goes out, because burning uses up the oxygen inside the glass.
- Plants take in carbon dioxide and give out oxygen.
- It is full of air; air takes up space even though we cannot see it.
- Any two: plant trees, walk or cycle for short trips, share vehicles, do not burn garbage.
- Vehicle smoke adds more dust and dirt to the air near the road.