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Nature's Treasures

NCERT Class 6 · Science Based on NCERT Class 6 Science textbook · Free CBSE study kit

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Chapter Notes

Overview
This chapter introduces students to the various natural resources that are essential for life on Earth, such as air, water, sunlight, forests, soil, rocks, minerals, and fossil fuels. It explains how these resources are obtained from nature, how they are used in our daily lives, and why they must be conserved. The one big idea a student must walk away with is that all living beings depend on nature's treasures for survival, and we must use them responsibly to ensure they are available for future generations.
Key Concepts (13)
Natural resources
Resources which we get from nature are called natural resources.
e.g. Air, water, sunlight, forests, soil, rocks, minerals, and fossil fuels are all natural resources.
Human-made resources
All such resources created by human beings are called human-made resources.
e.g. Electric bulbs, furniture, solar panels, and bicycles are human-made resources.
Renewable resources
Resources which get renewed, replenished or restored within a reasonable period of time are called renewable resources.
e.g. Air, water, and forests are renewable resources because nature renews them.
Non-renewable resources
Resources that are found in limited quantities and once used, they get exhausted; they are not produced or replenished within a reasonable period of time.
e.g. Minerals, soil, rocks, coal, petroleum, and natural gas are non-renewable resources.
Fossil fuels
Fuels formed essentially from the remains of microorganisms and plants that got buried deep inside the earth, and were converted to petroleum, natural gas and coal over millions of years.
e.g. Petrol, diesel, kerosene, coal, and natural gas are fossil fuels.
Wind
Moving air is called wind.
e.g. When a firki (paper pinwheel) rotates when you blow air on it or run with it, that is due to wind.
Rainwater harvesting
A method of conserving water in which rainwater is collected and stored in large quantities for later use.
e.g. In many buildings, rainwater is collected from rooftops and stored in tanks for later use.
Forests
Forests are large areas with dense growth of various types of plants.
e.g. The forest near Ajji's village in the Western Ghats has many herbs, shrubs, and trees.
Soil
Soil is formed by the disintegration (breaking apart) of rocks by actions of the Sun, water and living organisms over a long time (thousands of years).
e.g. Soil from a farm after ploughing contains small pebbles, roots of plants, and earthworms.
Minerals
Rocks are made up of minerals; important metals such as aluminium, gold, copper and iron are extracted from minerals.
e.g. Basic mobile phones contain about a dozen minerals like gold, silver, copper, and cobalt.
Stepwells
Traditional water harvesting structures commonly known as Bawadi in Rajasthan and Vav in Gujarat, built to store rainwater and water seeping from nearby lakes, ponds and rivers.
e.g. Toorji ka Jhalra in Jodhpur, Rajasthan is a stepwell.
Van Mahotsav
A week-long event celebrated across the country during the month of July, during which new plants and trees are planted, and awareness about respecting forests is raised.
e.g. During Van Mahotsav, students and communities plant trees to increase the green cover.
Chipko movement
A famous movement started in the early 1970s in Uttarakhand where local women encircled and hugged trees to protect them from being felled.
e.g. Women in Uttarakhand hugged trees to prevent them from being cut down.
How It Works
Composition of Air
  1. Air is a mixture of gases.
  2. It contains nitrogen (78%), oxygen (21%), and argon, carbon dioxide and other gases (1%).
  3. Oxygen in air is essential for the survival of most living beings.
💡 Students often forget that nitrogen is the most abundant gas in air (78%), not oxygen.
Formation of Fossil Fuels
  1. Remains of microorganisms and plants get buried deep inside the earth.
  2. Over millions of years, these remains are converted into petroleum, natural gas, and coal.
  3. These fuels are called fossil fuels and are non-renewable because they take millions of years to form.
💡 Students often think fossil fuels come from dinosaurs; the chapter says they come from microorganisms and plants.
Formation of Soil
  1. Rocks are broken apart (disintegrate) by the actions of the Sun, water, and living organisms.
  2. This process takes thousands of years.
  3. The resulting material forms soil, which contains sand, insects, worms, and decomposed plants and animals.
💡 Students often think soil forms quickly; it actually takes thousands of years.
Rainwater Harvesting
  1. Rainwater is collected from rooftops or other surfaces.
  2. It is stored in tanks or allowed to seep into the ground.
  3. The stored water can be used later for various purposes.
💡 Students often confuse rainwater harvesting with just collecting water in buckets; it involves systematic collection and storage.
How a Windmill Works
  1. Wind rotates the wings of a windmill.
  2. The rotating wings can be used to run flour mills, pull up water from a well, or generate electricity.
  3. A windmill farm has many windmills that use wind energy to generate electricity.
💡 Students often think windmills only generate electricity; they can also be used for grinding grain or pumping water.
Energy Flow from the Sun
  1. The Sun is the main source of energy on Earth.
  2. Plants use sunlight to make food.
  3. Animals eat plants and get energy.
  4. Humans get food from both plants and animals.
  5. Thus, all living beings are dependent on the Sun as the main source of energy.
💡 Students often think animals get energy directly from the Sun; they get it indirectly by eating plants or other animals.
Exam Traps — Don't Make These Mistakes
⚠ Confusing renewable and non-renewable resources
✗ Soil is a renewable resource because we can grow plants in it again.
→ Soil takes thousands of years to form and is not replenished within a reasonable period of time; it is classified as a non-renewable resource in the chapter.
✓ Soil is a non-renewable resource because it takes thousands of years to form and is not replenished quickly.
⚠ Thinking water is unlimited because it rains
✗ Water is a renewable resource, so we can use as much as we want.
→ Although water is renewable, freshwater is limited and easily accessible only in small amounts; we must use it judiciously and avoid wastage.
✓ Water is a renewable resource, but freshwater is limited and we must conserve it by using it carefully and avoiding pollution.
⚠ Mistaking human-made resources for natural resources
✗ A solar panel is a natural resource because it uses energy from the Sun.
→ Solar panels are created by human beings using natural resources; they are human-made resources, not natural resources.
✓ A solar panel is a human-made resource because it is created by humans using materials from nature.
⚠ Thinking all fossil fuels are the same
✗ Petrol, diesel, and CNG are all the same type of fuel.
→ Petrol and diesel are obtained from petroleum, while CNG is compressed natural gas; they are different fossil fuels with different properties.
✓ Petrol and diesel are obtained from petroleum, while CNG is compressed natural gas; all are fossil fuels but different types.
⚠ Confusing the composition of air
✗ Air is mostly oxygen.
→ Air contains 78% nitrogen and only 21% oxygen; nitrogen is the most abundant gas.
✓ Air is a mixture of gases: 78% nitrogen, 21% oxygen, and 1% other gases.
Compare & Contrast
Ability to be replenished within a reasonable period
Renewable resources
Non-renewable resources
Renewable resources get renewed or replenished by natural processes within a reasonable time (e.g., air, water, forests), while non-renewable resources are found in limited quantities and take millions of years to form, so they get exhausted once used (e.g., coal, petroleum, minerals).
Source of the resource
Natural resources
Human-made resources
Natural resources are obtained directly from nature (e.g., air, water, sunlight), while human-made resources are created by human beings using natural resources (e.g., electric bulbs, furniture, solar panels).
Exam Focus
Marks pattern: 2 MCQs (1 mark each), 1 Very Short Answer (1 mark), 1 Short Answer (3 marks), 1 Long Answer (5 marks)
Most asked: Classification of resources as renewable and non-renewable · Composition of air (percentages of gases) · Uses of water and water conservation methods like rainwater harvesting · Fossil fuels and their formation · Importance of the Sun as the main source of energy
Don't skip: Differentiate between renewable and non-renewable resources with examples (3-5 marks); Explain the composition of air with a diagram (3 marks); Describe the importance of water conservation and methods like rainwater harvesting (5 marks); Explain why fossil fuels are called non-renewable and suggest ways to conserve them (3-5 marks)
One-Line Revision (read aloud before the exam)
  1. Natural resources are resources we get from nature, such as air, water, sunlight, forests, soil, rocks, minerals, and fossil fuels.
  2. Human-made resources are created by humans using natural resources, for example, electric bulbs and solar panels.
  3. Renewable resources get replenished within a reasonable time, like air, water, and forests.
  4. Non-renewable resources are limited and take millions of years to form, like coal, petroleum, and minerals.
  5. Air is a mixture of gases: 78% nitrogen, 21% oxygen, and 1% other gases.
  6. Oxygen in air is essential for the survival of most living beings.
  7. Moving air is called wind; windmills use wind energy to grind grain, pump water, or generate electricity.
  8. Water is essential for drinking, cooking, bathing, washing, and growing crops.
  9. Freshwater is limited; most water on Earth is saline and not fit for use.
  10. Rainwater harvesting is a method of collecting and storing rainwater for later use.
  11. Forests are large areas with dense plant growth; they provide food and shelter to animals.
  12. Soil is formed by the breaking apart of rocks over thousands of years.
  13. Fossil fuels like coal, petroleum, and natural gas are formed from remains of microorganisms and plants over millions of years.
  14. The Sun is the main source of energy on Earth; plants use sunlight to make food.
  15. We must use natural resources judiciously to save them for future generations.
  16. The Chipko movement involved women hugging trees to protect them from being cut down.

MCQs — 10 Questions with Answers

Q1. What percentage of air is nitrogen?

  • A. 78% ✓
  • B. 21%
  • C. 1%
  • D. 50%

Answer: A — According to the composition of air shown in the chapter, nitrogen makes up 78 out of every 100 parts of air.

Q2. Why do we need oxygen?

  • A. To make plants grow
  • B. For our body to perform its functions ✓
  • C. To create wind
  • D. To keep water fresh

Answer: B — The chapter states that oxygen in the air we breathe is essential for our body to perform its functions and for our survival.

Q3. What is moving air called?

  • A. Breeze
  • B. Storm
  • C. Wind ✓
  • D. Oxygen

Answer: C — The chapter defines moving air as wind, which can blow fast during a storm or gently as a breeze.

Q4. Which of these is NOT a source of freshwater?

  • A. Rivers
  • B. Lakes
  • C. Oceans ✓
  • D. Wells

Answer: C — Oceans contain saltwater, not freshwater; rivers, lakes, and wells contain freshwater that we can use.

Q5. Fill in the blank: A __________ is an area with many windmills that generate electricity.

  • A. wind farm ✓
  • B. power plant
  • C. factory
  • D. village

Answer: A — The chapter defines a windmill farm as an area with a large number of windmills that use wind energy to generate electricity.

Q6. If you turn off the tap while brushing your teeth, what will happen?

  • A. Water will become polluted
  • B. Water wastage will be reduced ✓
  • C. Wind will stop blowing
  • D. Oxygen will increase in air

Answer: B — Turning off taps when not in use is one of the ways to reduce water wastage as mentioned in Activity 11.3.

Q7. Looking at the air composition diagram, what does the largest section represent?

  • A. Oxygen because we breathe it
  • B. Nitrogen because it is 78% of air ✓
  • C. Carbon dioxide because plants need it
  • D. Argon because it is important for survival

Answer: B — In Fig. 11.1, nitrogen occupies 78 out of 100 squares, making it the largest section of air composition.

Q8. Which statement correctly explains why freshwater is precious?

  • A. Because it is found only in oceans
  • B. Because most of Earth's water is salty and only a small amount of freshwater is easily accessible ✓
  • C. Because we use it only for drinking
  • D. Because windmills need freshwater to work

Answer: B — The chapter explains that water covers two-thirds of Earth but most is saltwater, and freshwater that is easily accessible is found in limited amounts in ponds, rivers, lakes, and wells.

Q9. How does a firki help us understand air?

  • A. It shows that air has no weight
  • B. It demonstrates that moving air (wind) has the power to push and rotate objects ✓
  • C. It proves that air is made of oxygen only
  • D. It shows that air is invisible

Answer: B — Activity 11.2 shows that when you blow air on a firki or move it through air, it rotates because wind (moving air) pushes it.

Q10. What is the main cause of water pollution mentioned in the chapter?

  • A. Too much rain falling
  • B. Throwing trash and waste from homes and industries into water sources ✓
  • C. Using water for cooking and drinking
  • D. Wind mixing with water

Answer: B — The chapter clearly states that we pollute freshwater by throwing trash and waste from homes and industries into water sources like rivers and lakes.

Flashcards

What percentage of air is oxygen?

Oxygen makes up 21% of the air we breathe.

Why can't we hold our breath for a long time?

Our body needs oxygen to function, and holding breath stops oxygen from entering our lungs.

What is wind?

Wind is air that is moving from one place to another.

How does a firki work?

Wind pushes the folded paper wings of a firki, making it spin around.

What percentage of Earth's water is saltwater?

About two-thirds of Earth is covered in water, and most of it is salty ocean water.

Why is freshwater precious?

Freshwater is precious because only a small amount is easily available for drinking and farming, while most of Earth's water is salty.

Name three uses of water in daily life.

Water is used for drinking, cooking, bathing, washing, cleaning, and growing crops.

What is a windmill farm?

A windmill farm is an area with many windmills that use wind energy to generate electricity.

How does water get polluted?

Water becomes polluted when trash, waste from homes, and waste from industries are dumped into rivers, lakes, and other water sources.

What are two ways to reduce water wastage?

We can reduce water wastage by turning off taps when not using them and fixing water leaks quickly.

Important Board Questions

What is the main gas in air that we need to survive? [1 mark]

Look at the composition of air (Fig. 11.1) — it's not nitrogen (78%) or argon. Remember Activity 11.1 where you held your breath.

Name any two uses of water in daily life and explain why water is precious. [2 marks]

Water is used for drinking, cooking, bathing, washing, and crops. Water is precious because most of Earth's water is salty and only small amounts of freshwater are easily available.

Explain with an example from daily life how water is wasted at home. How can this wastage be reduced? [3 marks]

Choose any activity from Table 11.1 like hand washing, brushing teeth, or showering. Explain how water runs without being used. Give one way to reduce it like turning off taps or fixing leaks.

Describe how a windmill works and explain how windmill farms in India help us. Draw and label a simple diagram of a windmill. [5 marks]

Wind moves and rotates the wings of a windmill. This rotation can generate electricity. Name Indian windmill farms like Muppandal (Tamil Nadu) or Jaisalmer (Rajasthan). Draw a windmill with blades/wings and label them.

True or False: Saltwater from oceans can be used directly for drinking and farming. Give a reason for your answer. [2 marks]

This is False. Saltwater is not fit for drinking, agriculture, or industry. We need freshwater from rivers, lakes, wells, and underground sources.

Assertion-Reason Questions for Nature's Treasures

Q1. Assertion (A):

We need to use water carefully and not waste it.

Reason (R):

Only a very small fraction of freshwater on Earth is easily accessible to us.

Answer: A — Both A and R are true, and R is the correct explanation of A — Both the assertion and reason are true, and the reason correctly explains why water should be used carefully. Most freshwater is frozen or underground, making easily accessible freshwater precious and limited.

Q2. Assertion (A):

Windmills are important for generating electricity in India.

Reason (R):

Wind energy is a natural treasure that can be used as a source of power.

Answer: B — Both A and R are true, but R is NOT the correct explanation of A — Both statements are true, but the reason does not fully explain the assertion. Windmills are important because they efficiently convert wind energy into electricity, not just because wind is a natural treasure.

Q3. Assertion (A):

We cannot survive without oxygen for more than a few minutes.

Reason (R):

Oxygen is the most abundant gas in the air.

Answer: C — A is true but R is false — The assertion is true because our body needs oxygen constantly to function. However, the reason is false because nitrogen (78%), not oxygen (21%), is the most abundant gas in air.

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Case-Based Questions (CBQ) for Nature's Treasures

Case Study:

Ravi's mother is washing clothes in the backyard of their home in Mumbai. She leaves the tap running while soaping the clothes, letting water flow continuously. Ravi remembers learning about water conservation in his science class. He also recalls visiting his grandmother's village in the Western Ghats during vacation, where he learned how precious freshwater is. Ravi decides to help his mother save water by suggesting better methods.

Q1. What is the main water wastage happening in Ravi's home?

  • A. Using water for cooking
  • B. Leaving the tap running continuously while soaping clothes ✓
  • C. Washing clothes with soap
  • D. Water flowing into the garden

Answer: B

Q2. Which method would help Ravi's mother reduce water wastage while washing clothes?

  • A. Wash clothes more quickly
  • B. Turn off the tap while soaping and turn it on only for rinsing ✓
  • C. Wash fewer clothes at a time
  • D. Use less soap on the clothes

Answer: B

Q3. Why did Ravi's visit to the Western Ghats help him understand the importance of water conservation?

  • A. He saw many rivers and lakes there
  • B. His grandmother taught him that freshwater is precious and only a small fraction is easily accessible ✓
  • C. The weather was very dry there
  • D. There was no water available in that region

Answer: B

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