Tamil Nadu (TNBSE) chapters aren't published yet — showing the NCERT equivalent

Tamil Nadu uses Samacheer Kalvi textbooks, not NCERT. Use this for the concepts; check chapter names and order against your own textbook.

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

  • 1Explain what fossil fuels are and how they form
  • 2Distinguish renewable from non-renewable energy
  • 3Name common fuels and their uses
  • 4Explain why fossil fuels will run out
  • 5Suggest ways to conserve fuel and use renewable energy
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Why this chapter matters
'What If It Finishes' explains fossil fuels, why they are running out, and the renewable alternatives that can replace them. It teaches children the difference between non-renewable and renewable energy and the importance of conserving fuel for the future.

Before you start — revise these

A 5-minute refresher here will save you 30 minutes of confusion below.

What If It Finishes — Class 5 EVS (CBSE)

Based on the NCERT Looking Around Grade 5 textbook. Learn about the fuels we use and why conservation is essential, then solve the practice set.


1. Why this chapter matters

We use fuels every day — in cars, buses, kitchens, factories, and power plants. But many of these fuels are non-renewable — once they run out, they will be gone forever. This chapter helps students understand what fossil fuels are, how they are formed, what they are used for, and why we must conserve them. It also introduces renewable energy sources that can replace fossil fuels in the future.

2. What are fossil fuels?

Fossil fuels are made from the remains of ancient plants and animals that lived millions of years ago. Over time, heat and pressure transformed them into coal, oil, and natural gas.

Fossil fuelHow it formedFound as
CoalFrom ancient forests buried under earthSolid black rock
Petroleum (crude oil)From tiny sea creatures buried under seaThick liquid
Natural gasFrom organic matter under heat and pressureGas

Why are they called 'fossil' fuels?

Because they are made from fossils — the remains of ancient living things. It took millions of years to form them.

3. Types of fuels we use

FuelWhere it is usedRenewable?
PetrolCars, two-wheelers, small enginesNo (non-renewable)
DieselTrucks, buses, tractors, generatorsNo
CNG (Compressed Natural Gas)Buses, cars, auto-rickshaws, kitchenNo (but cleaner)
LPG (Liquefied Petroleum Gas)Cooking gas cylindersNo
KeroseneStoves, lamps (in some areas)No
CoalPower plants, factoriesNo
FirewoodCooking in rural areasYes (but limited)
Cow dung cakesCooking in rural areasYes

4. Why fossil fuels will finish

Fossil fuels are non-renewable. This means:

  • They take millions of years to form.
  • We are using them much faster than they can form.
  • At current usage rates, oil may last 50-70 years and coal about 100-150 years.
  • Once they are gone, we cannot make more.

What happens when they finish?

  • Vehicles stop running (no petrol, diesel, CNG).
  • Electricity from coal plants stops.
  • Cooking becomes difficult (LPG runs out).
  • Industries shut down.
  • Life as we know it would change completely.

5. Renewable energy alternatives

Renewable energy comes from sources that will not run out.

Renewable sourceHow it worksUsed in India?
Solar energySunlight is converted to electricity using solar panelsYes, growing rapidly
Wind energyWind turns turbines to generate electricityYes, especially in Tamil Nadu, Gujarat
HydropowerFlowing water turns turbinesYes, many dams
BiogasGas produced from cow dung and organic wasteYes, in villages
Tidal energyEnergy from ocean tidesStarting

Which is better?

Renewable energy is better because:

  • It will never run out.
  • It does not pollute the air.
  • It does not contribute to climate change.
  • It can be produced locally.

6. How to conserve fuels

At home

  • Turn off lights and fans when not in use.
  • Use pressure cookers to save cooking gas.
  • Take shorter baths (saves energy for heating water).
  • Use public transport or cycle instead of a car.

In the community

  • Walk or use a bicycle for short distances.
  • Share rides (car-pool) to school or work.
  • Use energy-efficient appliances (LED bulbs, 5-star rated appliances).
  • Plant trees — they absorb CO2 from burning fuels.

7. Activity corner

Activity 1: Make a list of all the fuels used in your home in one week (LPG, petrol, electricity, kerosene, etc.). Discuss with your family how each could be used more carefully.

Activity 2: Find out about the solar panels in your area. Visit a building that uses solar energy and learn how it works.

Activity 3: Create a poster with the message 'Save Fuel — Save the Future'. Display it in your school.

8. Common mistakes

  • Mistake: Thinking CNG and LPG are renewable Fix: They are cleaner than petrol/diesel but still non-renewable (made from natural gas and petroleum).
  • Mistake: Believing fossil fuels are unlimited Fix: Fossil fuels took millions of years to form. We are using them in hundreds of years. They will run out.
  • Mistake: Thinking renewable energy cannot replace fossil fuels at all Fix: Renewable energy can replace fossil fuels, but we need technology and investment to make it affordable for everyone.

9. Key facts

  • Fossil fuels: coal, petroleum, natural gas — non-renewable.
  • They took millions of years to form.
  • At current rates, oil may last ~60 years, coal ~150 years.
  • Renewable energy: solar, wind, hydro, biogas.
  • CNG and LPG are cleaner but still non-renewable.
  • Conserve fuel: turn off appliances, use public transport, walk or cycle.
  • India is rapidly growing its renewable energy capacity.

10. Self-test

  1. What are fossil fuels? Give two examples.
  2. Why are fossil fuels called 'non-renewable'?
  3. Name two renewable sources of energy.
  4. Why is CNG considered better than petrol even though both are non-renewable?
  5. What is one way you can save fuel at home?

11. Answer key

  1. What are fossil fuels? Give two examples. Answer: Fossil fuels are energy sources formed from ancient living things. Examples: coal, petroleum (oil), natural gas.

  2. Why are fossil fuels called 'non-renewable'? Answer: Because they take millions of years to form and are being used up much faster than they can be replaced.

  3. Name two renewable sources of energy. Answer: Solar energy and wind energy (also hydropower, biogas, tidal energy).

  4. Why is CNG considered better than petrol even though both are non-renewable? Answer: CNG burns more cleanly than petrol, producing less air pollution.

  5. What is one way you can save fuel at home? Answer: Turn off lights and fans when not in use. (Also: use pressure cooker, walk/cycle for short trips.)

12. Quick revision

  • Fossil fuels = coal, petroleum, natural gas (non-renewable).
  • They will run out — oil ~60 years, coal ~150 years.
  • Renewable alternatives: solar, wind, hydro, biogas.
  • CNG and LPG are cleaner but still finite.
  • Conserve: use less, switch to renewable, walk/cycle.
  • India is building solar and wind capacity.
  • Saving fuel saves money, reduces pollution, and protects the future.
  • Small daily habits make a big difference.

Key formulas & results

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

Fossil fuels
Coal, petroleum, natural gas (non-renewable)
Formed from ancient living things over millions of years.
Renewable energy
Solar, wind, hydro, biogas, tidal
Sources that will not run out and do not pollute.
⚠️

Common mistakes & fixes

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

WATCH OUT
✗ Thinking CNG and LPG are renewable
✓ They burn cleaner than petrol and diesel but are still non-renewable, made from natural gas and petroleum.
WATCH OUT
✗ Believing fossil fuels are unlimited
✓ They took millions of years to form and are being used up in hundreds of years, so they will run out.
WATCH OUT
✗ Thinking renewable energy cannot replace fossil fuels
✓ Renewable energy can replace them, but it needs technology and investment to become affordable for all.

NCERT exercises

Every NCERT exercise from this chapter — what it covers and how many questions to expect.

Think and Discuss
Think and Discuss
Questions on fuels and conservation
4
Questions
Find Out
Find Out
Fuels used at home and renewable energy nearby
4
Questions

Practice problems

Work through this chapter's problems as a readiness check — reveal each solution, mark yourself honestly, and get your gap report at the end.

Readiness check

Are you exam-ready for What If It Finishes?

4 problems from this chapter. Try each one, reveal the worked solution, mark yourself honestly — get your gap report at the end.

4 questions~3 min worth ~5 marks in Tamil Nadu (TNBSE) exams

5-minute revision

The whole chapter, distilled. Read this the night before the exam.

  • •Fossil fuels (coal, petroleum, natural gas) are non-renewable.
  • •They formed from ancient living things over millions of years.
  • •Oil may last about 60 years and coal about 150 years at current use.
  • •Renewable energy: solar, wind, hydro, biogas, tidal.
  • •CNG and LPG are cleaner but still finite.
  • •Conserve fuel: switch off appliances, use public transport, walk or cycle.
  • •India is rapidly expanding its solar and wind energy.

Tamil Nadu (TNBSE) marks blueprint

Where the marks come from in this chapter — so you can plan your prep.

Typical chapter weightage: 3-5 marks, depending on the school paper

Question typeMarks eachTypical countWhat it tests
Very Short / MCQ1-21-2Fuels and renewable sources
Short Answer2-31Why fuels finish and how to conserve
Prep strategy
  • Learn what fossil fuels are and how they form
  • Separate renewable from non-renewable energy
  • Understand why fossil fuels will run out
  • List ways to save fuel

Where this shows up in the real world

This chapter isn't just an exam topic — it lives in the world around you.

Saving energy

Conservation habits reduce fuel use and electricity bills.

Clean energy

Solar and wind power provide pollution-free electricity.

Protecting the future

Using less fossil fuel safeguards resources for coming generations.

Exam strategy

Battle-tested tips from teachers and toppers for this chapter.

1
Define fossil fuels and give examples
2
Explain why they are non-renewable
3
Name renewable energy sources
4
Suggest practical conservation steps

Going beyond the textbook

For olympiad aspirants and curious learners — topics that build on this chapter.

STRETCH
Find out how solar panels turn sunlight into electricity.
STRETCH
List the appliances at home and how each could use less energy.

Where else this chapter is tested

CBSE board isn't the only one — other exams test this chapter too.

CBSE Class 5 School ExamHigh
EVS / environment OlympiadMedium

Questions students ask

The real ones — pulled from the Q&A community and tutor sessions.

Fossil fuels like coal, oil, and natural gas took millions of years to form, but we are burning them in just a few hundred years, so they will eventually run out and cannot be replaced. Burning them also pollutes the air and contributes to climate change. Renewable sources such as solar, wind, hydro, and biogas will never run out, can be produced locally, and cause far less pollution. Conserving fuel and using renewable energy protects both our future supply and the environment.

If fossil fuels ran out, much of daily life would change dramatically. Vehicles that run on petrol, diesel, and CNG would stop, electricity from coal-fired power plants would fail, cooking with LPG would become difficult, and many factories would shut down. This is why it is so important to use fossil fuels carefully and to develop renewable energy sources that can take their place before they are exhausted.
Verified by the tuition.in editorial team
Last reviewed on 30 May 2026. Written and reviewed by subject-matter experts — read about our process.
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