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Tamil Nadu (TNBSE)Class 6 Science★ 6-10 marks in the TN Class 6 Term 3 exam through book-back MCQs, fill-ups, true/false and short answers

Water

Samacheer Kalvi (TN State Board) Class 6 Science — Term 3 Chapter 2, Water. How much water is fresh, the water (hydrological) cycle of evaporation, transpiration, condensation and precipitation, sources of water, dams and conservation, with the actual book-back questions, common mistakes and quick revision.

⏱ 14 min readEasy difficulty✓ Free · NCERT-aligned

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Key points, glossary and the questions most likely to show up.

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

1State how much of Earth's water is salty and fresh
2Describe the water cycle stages
3Differentiate evaporation and condensation
4Explain the role of a dam
5Suggest ways to conserve water

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Why this chapter matters

Water teaches how little fresh water exists and how the water cycle renews it — vital for conservation. The water cycle, the 97% salty figure and dams are directly tested book-back content in the TN Class 6 Term 3 exam.

Before you start — revise these

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

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Term 1 — Matter Around Us

States of matter.

Water — Class 6 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 6 Science, Term 3 — Chapter 2. The most precious resource.

1. About this chapter

This chapter covers how much water is fresh, the water cycle, the sources of water, dams, and water conservation.

2. Water on Earth

About 97% of the Earth's water is salty (in seas and oceans); only 3% is freshwater, and only about 0.3% is available for human use (rivers, lakes, ponds).
The human body needs about 2–3 litres of water daily.

3. The water cycle

The water (hydrological) cycle is the continuous movement of water. The heat of the sun causes evaporation from oceans, lakes and rivers; plants add vapour by transpiration.
The vapour rises, cools and condenses into clouds, then falls back as precipitation (rain). Distillation is NOT part of the water cycle.
Condensation forms dew on grass; evaporation is the change of water into vapour.

4. Sources and storage

About 30% of freshwater is groundwater. A dam is built across a river to regulate the flow and store water.
Water levels in rivers rise greatly during the rainy season.

5. Worked examples

Example 1. What percentage of Earth's water is salty? About 97%.

Example 2. Which process is NOT part of the water cycle — evaporation or distillation? Distillation.

Example 3. What is the water cycle also called? The hydrological cycle.

6. Book-back questions (Samacheer Kalvi)

I. Choose the correct answer

Around 97% of water on Earth is — (a) fresh / (b) salty. Ans: (b) salty.
Which is NOT part of the water cycle? — (a) evaporation / (b) distillation. Ans: (b) distillation.
The processes that add water vapour to the atmosphere are — (a) only rain / (b) transpiration and evaporation. Ans: (b) transpiration and evaporation.
About 30% of freshwater is found as — (a) rivers / (b) groundwater. Ans: (b) groundwater.
The best use of the water expelled by an R.O. plant is to — (a) throw it away / (b) use it for watering plants. Ans: (b) water plants.

II. Fill in the blanks 6. Only 0.3 percent of natural water is available for human consumption. 7. The process of changing water into vapour is called evaporation. 8. A dam is built on rivers to regulate water flow. 9. The water cycle is also called the hydrological cycle.

III. True or False 10. Evaporation occurs only in sunlight. — True. 11. Condensation forms dew on grass. — True. 12. Seawater can be used directly for irrigation. — False.

7. Common mistakes

Mistake: Thinking most of Earth's water is drinkable. Fix: 97% is salty; only about 0.3% is available for use.
Mistake: Counting distillation as part of the water cycle. Fix: The water cycle is evaporation, transpiration, condensation and precipitation — not distillation.
Mistake: Confusing evaporation and condensation. Fix: Evaporation = water to vapour; condensation = vapour to water (dew).

8. Quick revision

Term 3 · Ch 2 · water.
97% salty, 3% fresh, only ~0.3% available; body needs 2–3 L/day.
Water cycle (hydrological): evaporation + transpiration → condensation → precipitation.
~30% of freshwater is groundwater; a dam regulates river flow.
Reuse R.O. waste water for plants; conserve water.

Key formulas & results

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

Distribution

97% salty, 3% fresh, ~0.3% usable

Very little is drinkable.

Water cycle

evaporation + transpiration -> condensation -> precipitation

Also called hydrological cycle.

Daily need

2-3 litres per person per day

For the body.

Dam

built across a river to regulate flow and store water

~30% of freshwater is groundwater.

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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

✗ Thinking most of Earth's water is drinkable

✓ 97% is salty; only about 0.3% is available for use.

WATCH OUT

✗ Counting distillation as part of the water cycle

✓ The water cycle is evaporation, transpiration, condensation and precipitation — not distillation.

WATCH OUT

✗ Confusing evaporation and condensation

✓ Evaporation = water to vapour; condensation = vapour to water (dew).

NCERT exercises (with solutions)

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

Choose the correct answer

Book-back MCQs on salty water, the water cycle, vapour, groundwater and R.O. water.

Questions

Fill in the blanks

0.3%, evaporation, dam and hydrological cycle.

Questions

True or False

Evaporation, condensation and seawater irrigation.

Questions

Practice problems

Try each one yourself before tapping "Show solution". Active recall > rereading.

Q1EASY· MCQ

Around 97% of water on Earth is ____.

▶ Show solution

salty.

Q2EASY· MCQ

Which is NOT part of the water cycle (evaporation / distillation)?

▶ Show solution

distillation.

Q3EASY· Fill in the blanks

Only ____ percent of natural water is available for human consumption.

▶ Show solution

0.3.

Q4EASY· Fill in the blanks

The process of changing water into vapour is called ____.

▶ Show solution

evaporation.

Q5EASY· Fill in the blanks

The water cycle is also called the ____ cycle.

▶ Show solution

hydrological.

Q6EASY· True or False

Seawater can be used directly for irrigation. (True/False)

▶ Show solution

False.

5-minute revision

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

•Term 3 Chapter 2 of Samacheer Kalvi Class 6 Science.
•About 97% of Earth's water is salty; only 3% is fresh and just 0.3% is available for use.
•The water (hydrological) cycle: the sun's heat causes evaporation, plants add vapour by transpiration, vapour condenses into clouds and falls as precipitation.
•Distillation is not a part of the water cycle.
•About 30% of freshwater is groundwater; a dam is built across a river to regulate flow.
•The body needs 2-3 litres of water daily; we must conserve and reuse water.

Tamil Nadu (TNBSE) marks blueprint

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

Typical chapter weightage: 6-10 marks across book-back MCQ, fill-ups, true/false and short answers

Question type	Marks each	Typical count	What it tests
MCQ / Fill / T-F	1	5-7	Distribution, water cycle, dams
Short Answer	2	1-2	Water cycle stages, conservation

Prep strategy

Remember 97% salty, 0.3% usable
Learn the water-cycle stages in order
Separate evaporation and condensation
Note the role of a dam

Where this shows up in the real world

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

Conservation

Understanding water scarcity drives saving water.

Agriculture

Dams and the water cycle support farming.

Weather

The water cycle explains rain and clouds.

Exam strategy

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

Quote 97% salty and 0.3% usable
List the water-cycle stages in order
Separate evaporation and condensation
Explain the use of a dam

Going beyond the textbook

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

Draw and label the water cycle.
Explain how rainwater harvesting recharges groundwater.

Where else this chapter is tested

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

TN Class 6 Term 3 ExamHigh

NMMS / Foundation ScienceMedium

School unit testsHigh

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Questions students ask

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

Most of that water (about 97%) is salty seawater, and only a tiny fraction (around 0.3%) is fresh and available for drinking, so the usable supply is very small and must be conserved.

Evaporation is liquid water turning into vapour using the sun's heat, while condensation is water vapour cooling and turning back into tiny water droplets, as in clouds or dew.

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