Chapter 10 of 10

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Tamil Nadu (TNBSE)Class 5 Science★ 5-6 marks in TN Class 5 Term 3 exams — composition of air, properties, air pollution, and air-related phenomena

Air

Samacheer Kalvi (TN State Board) Class 5 Science — Chapter 10, Air. Air pollution, weather and climate. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

⏱ 12 min readMedium difficulty✓ Free · NCERT-aligned

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By the end of this chapter you'll be able to…

1State the composition of air: Nitrogen ~78%, Oxygen ~21%, Argon ~0.9%, CO₂ ~0.04%, water vapour and other gases ~0.06%
2Demonstrate properties of air: occupies space (inverted glass experiment), has weight (inflated vs deflated balloon), exerts pressure (crushing can experiment — steam condenses, creating vacuum, atmospheric pressure crushes the can)
3Explain that warm air rises (candle pinwheel experiment) — this is convection, the principle behind hot air balloons and sea breezes
4Identify causes of air pollution (vehicles, factories, crackers, burning waste, crop stubble burning) and their effects (global warming — CO₂; acid rain — SO₂ and NO₂; respiratory diseases — PM2.5 and PM10)
5Explain global warming: increased CO₂ and other greenhouse gases trap heat in the atmosphere → Earth's average temperature rises → melting glaciers, rising sea levels, extreme weather

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Why this chapter matters

Air in Class 5 is the final primary school chapter on the atmosphere. Children revisit the composition of air with greater precision, study the properties of air through experiments, and connect air to real-world phenomena — why a bicycle pump gets hot (compression), why a straw works (air pressure), why aeroplanes fly (Bernoulli's principle in simple terms). The chapter also covers air pollution in depth, linking to global warming and climate change — topics that will dominate their middle and high school science. For a generation growing up in a warming world, understanding air is not just science — it is survival.

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Air — Class 5 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 5 Science, Chapter 10. Air pollution, weather and climate.

1. About this chapter

This chapter covers Air as part of the Class 5 Samacheer Kalvi Science curriculum. It deals with air pollution, weather and climate and builds conceptual understanding essential for the TN School Term Exam.

By the end of this chapter, students will be able to:

Explain causes and effects of air pollution
Describe basic weather phenomena

2. Key concepts

Concept 1: Explain causes and effects of air pollution.
Concept 2: Describe basic weather phenomena.

3. Important terms and formulas

Term / Formula	Description
Explain causes and effects…	Explain causes and effects of air pollution
Describe basic weather phenomena…	Describe basic weather phenomena

4. Worked examples

Example 1. Applying a key concept from this chapter.

Solution: Identify the relevant principle → apply the formula or rule → state the answer with correct units.

Example 2. A typical exam-style question on air.

Solution: Break the problem into steps, use the appropriate formula and verify the answer.

5. Common mistakes

Mistake: Skipping units or forgetting to state them. Fix: Always write units alongside every quantity and answer.
Mistake: Confusing similar terms or concepts in this chapter. Fix: Make a comparison table of the terms during revision.

6. Practice (exam-style)

Define the main term or principle covered in Chapter 10.
Give two real-life examples related to air.
Solve a short numerical or descriptive question from this chapter.
State one important formula and explain each symbol.

7. Answer key (hints)

Refer to section 2 (Key concepts) above for the definition.
Examples should be drawn from daily experience and local context.
Apply the formula from section 3, show all steps clearly.
Formula with units — refer to the textbook glossary for symbol meanings.

8. Quick revision

Class 5 Science — Chapter 10: Air.
Core idea: Air pollution, weather and climate.
Key outcomes: Explain causes and effects of air pollution; Describe basic weather phenomena.
Always revise diagrams / tables from the Samacheer Kalvi textbook before the exam.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Properties of air (with experiments)

Air occupies space → invert an empty glass into water — water does not enter because air occupies the space. Blow into a balloon → it expands because air occupies space. Air has weight → weigh a deflated balloon, then inflate and weigh again — the inflated balloon is heavier. Air exerts pressure → fill a can with a little water, heat until steam comes out, quickly invert into cold water — the can crushes! Steam condenses creating vacuum inside; outside atmospheric pressure (14.7 pounds per square inch) crushes the can.

The crushing can experiment is dramatic and memorable. It demonstrates that air pressure is not 'nothing' — it is a force of about 1 kg per square centimetre, pushing on everything from all directions.

Global warming and the Greenhouse Effect

Sunlight (short wave radiation) passes through the atmosphere and warms the Earth. The Earth re-radiates heat as long-wave (infrared) radiation. Greenhouse gases (CO₂, methane, water vapour, CFCs) in the atmosphere TRAP some of this heat, keeping Earth warm enough for life. This is the natural greenhouse effect — without it, Earth's average temperature would be −18°C instead of +15°C. PROBLEM: Human activities have increased CO₂ by ~50% since the industrial revolution (burning fossil fuels, deforestation). This ENHANCED greenhouse effect is causing global temperatures to rise — global warming.

The last 10 years (2016-2026) have been the hottest decade on record. Tamil Nadu has experienced more frequent heatwaves, irregular monsoons, and coastal erosion — all linked to climate change.

Convection — warm air rises

When air is heated, its molecules move faster and spread apart → the air becomes less dense (lighter) → it RISES. Cooler, denser air rushes in to take its place → this movement creates WIND. This is why: hot air balloons rise, chimney smoke goes up, sea breeze blows from sea to land during the day (land heats faster → air rises → cooler sea air rushes in), land breeze blows from land to sea at night (land cools faster → sea is warmer → air rises over sea → cooler land air rushes out).

Chennai's famous sea breeze in the evening is convection in action. After a hot day, the land cools while the Bay of Bengal retains warmth — creating the pleasant evening breeze that makes Marina Beach so popular.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Confusing weather (short-term) and climate (long-term)

✓ A cold day in summer is WEATHER — a temporary change. Global warming is CLIMATE — the long-term average temperature trend. One cold winter does not disprove global warming, just as one hot day does not prove it.

WATCH OUT

✗ Thinking the ozone hole and global warming are the same thing

✓ They are DIFFERENT problems. Ozone hole = depletion of the ozone layer (O₃) by CFCs, allowing harmful UV radiation to reach Earth. This causes skin cancer. Global warming = trapping of heat by greenhouse gases (CO₂, methane), causing Earth to warm. The ozone hole is being fixed (Montreal Protocol banned CFCs). Global warming is still getting worse.

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