Nature’s Treasures · Lesson 1 of 8
Air Around Us and the Power of Wind
“Discover why air supports life and how moving air can do useful work.”
• Explain why breathing supplies oxygen needed by the body. • Interpret the approximate composition of air using percentages. • Identify everyday signs of moving air and distinguish a breeze from stronger wind. • Describe how a pinwheel and windmill use moving air.
Air is a treasure we cannot see
Imagine Ajji and her grandchildren walking through a cool village near the Western Ghats. They can feel the fresh air but cannot see the air itself. It surrounds Earth and is essential to most living beings. We can investigate it by noticing what happens when we breathe and when it moves.
Breathing and the need for oxygen
Breathe in deeply and breathe out slowly. You may notice your chest moving as air enters and leaves your lungs. If you briefly hold your breath, the urge to breathe returns: your body needs a continuing supply of oxygen to carry out its functions. Most other living beings need oxygen too. Food and water can be absent for some time, but a person cannot live for long without oxygen.
Take a comfortable deep breath, breathe out slowly, then notice how you feel during only a brief, comfortable pause before your next breath. Stop at once if uncomfortable. The observation connects the need to breathe with the body’s need for oxygen; it is not a contest to hold your breath longest.
A mixture of gases surrounding Earth, including nitrogen, oxygen and small amounts of other gases.
What is in air?
Air is a mixture, so it contains several gases rather than only oxygen. If we represent the whole mixture by 100 equal parts, about 78 parts are nitrogen, 21 parts oxygen, and one part contains argon, carbon dioxide and other gases. The symbol % means “out of every 100 parts”. These are approximate proportions, not a claim that a breath contains exactly 100 visible pieces.
Problem
A diagram shows 100 equal squares of air. How many represent oxygen, and how many represent nitrogen and oxygen together?
- 1.Oxygen occupies 21 of the 100 squares, so its share is about 21%.
- 2.Nitrogen and oxygen together occupy 78 + 21 = 99 squares.
- 3.The remaining one square stands for argon, carbon dioxide and other gases.
We breathe air, which is a mixture. Oxygen is one important gas in that mixture; saying that all air is oxygen hides the much larger nitrogen share.
When air moves
Rustling leaves, fluttering book pages and swaying clothes are clues that air is moving even though we cannot see it. Moving air is called wind. A gentle wind is a breeze; wind can also blow strongly in a storm. Its motion can make other objects move.
Moving air.
Make a firki, or paper pinwheel, from a square sheet with careful adult help for cutting and pinning. Hold it where air moves, blow gently or walk while holding it. The firki rotates when moving air pushes its slanted paper blades. Compare its motion in still and moving air. The source illustration shows how cuts, folds and a central pin turn a square into a rotating toy.
Wind can do useful work
A windmill has large blades that rotate in moving air, much as the firki does. This turning can run a flour mill, lift water from a well or help generate electricity. A wind farm contains many windmills that use wind energy to make electricity. Muppandal in Tamil Nadu, Jaisalmer in Rajasthan and Brahmanvel in Maharashtra are examples named in the chapter.
Problem
A windmill turns on a windy day and helps raise water. Trace what makes that possible.
- 1.Moving air pushes the windmill blades.
- 2.The blades rotate, and the turning motion operates equipment attached to them.
- 3.The equipment lifts water; without suitable wind, the blades may not turn enough to perform the same work.
Quiz
Which gas makes up the largest share of air?
What does 21% oxygen mean in an approximate 100-part air diagram?
Which observation is evidence of moving air?
Why does a firki rotate when someone blows toward it?
What is a wind farm?
Which statement about breathing is most accurate?
Practice Problems
- Explain why it is uncomfortable to hold your breath for a long time, and state a safe way to observe breathing.
- Represent air using 100 squares. Label 78, 21 and 1 squares with their gas groups.
- Describe two visible effects of invisible moving air around your home or school.
- Explain why a firki and a windmill are related, and name two uses of windmills.
- If 100 equal squares depict air, how many remain after marking nitrogen and oxygen? What do they represent?
- Describe how a wind farm differs from one small pinwheel.
Key Takeaways
• Air is a mixture of gases, with approximately 78% nitrogen, 21% oxygen and 1% other gases. • Oxygen in the air is essential for our survival. • Wind is moving air, and it can turn a firki or the blades of a windmill. • Windmills can perform work such as pumping water and generating electricity.
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Water: Access, Use and Care