NCERT Solutions for Class 6 Science Chapter 11 Nature’s Treasures (PDF) – 2027

Yes. Besides pure air, fertile soil, sunlight and trees, nature gives us water, forests, wind, rocks and minerals, plants and animals (for food, milk, cotton, wool and honey), and fossil fuels such as coal, petroleum and natural gas. None of these is made by people.

I could hold my breath for about 30 seconds. (Most children of this age can manage about 25 to 45 seconds.)

We cannot hold it for long because our body needs oxygen all the time to carry out its functions.

I feel uncomfortable and restless. My chest feels tight, my heart beats faster and there is a strong urge to breathe. It is a great relief to breathe out and take in fresh air. This happens because the body is not getting the oxygen it needs.

Nitrogen, oxygen, argon and carbon dioxide. Air is a mixture of gases: about 78% nitrogen, about 21% oxygen, and about 1% argon, carbon dioxide and other gases together.

Yes, the firki rotates. It turns when we run holding it, when we blow on it, or when we move it back and forth. The harder the air pushes on its blades, the faster it spins.

The wind (moving air) makes a firki rotate. Moving air pushes against the slanted blades of the firki and turns it. A windmill works in the same way.

Some other windmill farms of India:

• Kayathar and Aralvaimozhi — Tamil Nadu
• Vankusawade (near Koyna) — Maharashtra
• Chitradurga and Gadag — Karnataka
• Kutch coast — Gujarat
• Anantapur — Andhra Pradesh

I feel very uneasy and restless. My mouth and throat go dry, I feel weak and tired, and I cannot think of anything except water. Thirst is the body’s signal that it needs water.

Other uses of water: cooking, bathing, washing clothes and utensils, cleaning the house, watering plants, giving water to animals, growing crops, and in industries.

Sources of water: rain, rivers, streams, lakes, ponds, springs, wells, tube wells and hand pumps (groundwater), snow and ice (glaciers), and oceans and seas.

Ocean water is salty, so for our daily needs we use freshwater from rivers, lakes, ponds and wells.

No, water is often not used efficiently. Yes, I have seen it being wasted — taps left running while brushing or soaping, leaking taps and pipes, overflowing tanks, and vehicles washed with a running hosepipe.

Here is Table 11.1 completed. Fill your own copy after watching what actually happens at your home.

Conclusion: a lot of water is wasted in small amounts many times a day — while brushing, bathing, washing and gardening. Most of it can be saved by changing small habits.

What my family can do: turn off taps when not in use, fix leakages at once, bathe with a bucket, reuse water for plants and cleaning, and harvest rainwater.

Human activities that pollute water: throwing trash and plastic into water bodies; letting sewage and factory waste into rivers; washing clothes, cattle and vehicles in ponds and rivers; and fertilisers and pesticides from fields being washed into water by rain.

What we can do: never throw waste into water, use less detergent, keep drains clean, and join clean-up drives.

Ways to conserve water:

• Turn off taps when not in use and fix leaks.
• Bathe with a bucket and mug.
• Reuse water — for example, use the water in which vegetables were washed to water plants.
• Harvest rainwater.
• Do not pollute water sources.

Traditional ways of harvesting water include the bawadi (stepwell), johad and tanka in Rajasthan, the vav (stepwell) in Gujarat, the eri (chain of village tanks) in Tamil Nadu and the kuhl (small channels) in Himachal Pradesh. Ask your elders which of these is found in your locality.

World Water Day (22 March) reminds everyone that freshwater is limited and precious. It was started by the United Nations. On this day people learn to save water and keep water sources clean, and work so that everyone gets safe drinking water.

More uses of the Sun’s heat and light (pictures to draw, with descriptions):

• Drying chillies and mango slices — so that they can be stored.
• Drying grain before storing it.
• Solar cooker — cooking food with the Sun’s heat.
• Solar water heater — heating water for bathing.
• Solar panels — making electricity.

Surya’s statement is correct. The cow gets its energy by eating grass, but the grass can grow only with the help of sunlight. So the energy reaches the cow from the Sun through the grass — the Sun is the main source of energy.

Bhoomi is right that the cow gets energy from the grass, and that just standing in the Sun does not feed it, but she stops at the grass.

1. We may have to depend on artificial lighting during day time also. (given)
2. It will become cold, and wet clothes and grain will not dry.
3. Plants will not be able to make food properly, so animals and people will get less food.

Also, solar panels, solar cookers and solar water heaters will not work.

Products we get from forests:

1. Wood (timber) for furniture, doors and houses
2. Firewood for cooking
3. Fruits such as amla (nellikai), jamun and tamarind
4. Honey and wax
5. Medicinal plants such as neem and tulsi
6. Gum, resin, bamboo and cane

Consequences of cutting a large forest area:

• The soil is washed away and the land becomes barren.
• Animals and birds lose their food and shelter.
• Rainwater runs off quickly, causing floods; later, wells dry up.
• The area becomes hotter, and the air less clean.
• People who depend on forests lose their livelihood.

Show these ideas through a story, poem, role play or presentation. A sample story is given in the explanation.

Collect four or five samples in separate paper packets and label each one. Here is Table 11.2 filled in with typical observations.

Yes. When we look closely, we find much more than we guessed. For example, I guessed that soil is just brown mud, but I found sand, small pebbles, bits of roots and leaves, and tiny insects and worms in it. The samples also had different colours.

Yes. Soil samples from different places differ in colour, texture, moisture and what they contain. Farm soil was dark brown and crumbly, playground soil was light brown, hard and sandy, and soil from under a tree was dark, damp and full of rotting leaves. They differ because they contain different materials.

Yes. The magnifying lens shows much more than the naked eye. With the naked eye, soil looks like a brown powder with a few pebbles and leaves. Through the lens we can see separate grains of different sizes and colours, tiny bits of roots and leaves, and very small creatures.

Soil is formed by the disintegration (breaking apart) of rocks by the action of the Sun, water and living organisms over a long time — thousands of years.

Rocks are made up of minerals. A rock is a natural mixture of one or more minerals. Important metals such as aluminium, gold, copper and iron are extracted from minerals.

Rocks and minerals are carried by trucks, goods trains and ships. Most of these vehicles run on fossil fuels such as diesel.

Because different types of vehicles use different types of fuels — for example petrol, diesel or CNG. Each vehicle goes to the filling station that sells the fuel it needs.

Stand safely near a road or in your colony for fifteen minutes and note down every vehicle you see. A filled Table 11.3 looks like this.

Petrol and diesel are the two most widely used fuels for vehicles. In most Indian surveys petrol comes first, because two-wheelers outnumber every other vehicle.

Major coal-producing states of India: Jharkhand, Odisha, Chhattisgarh, Madhya Pradesh, Telangana, West Bengal and Maharashtra. They are marked on the outline map below.

More ways to conserve fossil fuels:

• Share vehicles (car-pooling) and use the school bus.
• Switch off the engine at red lights.
• Cook in a pressure cooker and keep the lid on the pan.
• Use solar cookers and solar water heaters.
• Switch off lights and fans when not needed, because most of our electricity comes from coal.

Alternatives for reducing air pollution:

• Use electric vehicles and CNG vehicles.
• Use public transport, walk or cycle.
• Make electricity from the Sun and the wind.
• Plant more trees.
• Do not burn garbage or crop stubble.

Table 11.4 completed. Notice how almost every row ends up using more than one resource.

How many resources? My list uses nine kinds of natural resources — air, water, energy from the Sun, forests, soil, rocks, minerals, fossil fuels, and plants and animals. A friend’s list will not be exactly the same; compare the two and add what you missed.

Unjumbled names: ocrk → rock, refost → forest, ndiw → wind, atwre → water. The stone in Fig. 11.9 matches “ocrk” (rock); the other three pictures stand for a forest, wind and water.

New table with the classification:

(i) (b) Petrol. Scooters and motorbikes run on petrol.

(ii) (b) Water. Water is renewed by nature through the water cycle; coal, natural gas and petrol are non-renewable.

Because it takes millions of years to form, is present in limited quantity, and is not replenished within a reasonable period of time — once used, it is gone.

It is difficult to regrow forests because:

• Trees take many years (often 30 years or more) to grow big, so a new forest takes a very long time.
• When trees are cut, the soil is washed away, so new plants get poor soil.
• Animals and birds that spread seeds leave the area.
• A forest has many kinds of plants and animals living together; planting a few trees cannot bring all of them back.

1. Breathing — living beings take in oxygen from the air.
2. Burning of fuels — fuels need the oxygen of the air to burn.
3. Running windmills — moving air turns windmills to generate electricity.
4. Drying clothes — moving air helps wet clothes dry faster.

Actions I can take:

1. Plant saplings of native trees (neem, peepal, amla, jamun) at home, in school and along the road.
2. Water and protect the saplings until they grow.
3. Adopt a tree and look after it.
4. Grow plants in pots or in a kitchen garden.
5. Take part in Van Mahotsav and plantation drives.
6. Protect existing trees and ask others not to cut them.

(i) Solar energy (heat and light from the Sun) is being used. The food is being cooked in a solar cooker.

(ii) Benefit: it needs no fuel, so it is free and causes no smoke or air pollution.
Drawback: it works only in bright sunshine — not on cloudy days or at night.

Because trees protect the soil and keep it fertile.

• The roots of trees hold the soil. Without them, rain and wind carry away the fertile topsoil.
• Fallen leaves decay and add nutrients to the soil. With no trees, the soil loses its nutrients.
• Without shade the soil dries up and becomes hard, and earthworms and other organisms in it die.

Two ways human activities pollute the air:

1. Burning fuels in vehicles — petrol and diesel give out smoke and carbon dioxide.
2. Burning coal, garbage and crop stubble — in power plants, factories, brick kilns and fields; this fills the air with smoke and ash.

One action: use public transport, or walk or cycle for short distances, instead of using a separate vehicle.

• The solar panels will stop producing electricity, because they need sunlight.
• The gas stove will keep working, because it burns gas and does not need sunlight.
• The windmill will keep pumping water as long as the wind blows, because it is run by wind.

So the family will have little or no electricity, but it can still cook food and get water from the well.

The completed chart:

No, felling trees on a large scale is not justified.

Sample brief report: Wood is needed for industries and houses, but cutting forests on a large scale washes away the soil, destroys the homes of animals and birds, and harms people who depend on forests. A forest takes many years to grow again. So trees should be cut only as planned, and more trees should be planted than are cut. Recycling paper and using other materials also saves trees.

Sample plan to use less water in our school:

1. Form a water club and check all taps, tanks and toilets for leaks.
2. Get leaking taps and pipes repaired, and fit a float valve in the tank.
3. Put up “Close the tap” signs; water the garden with a can in the morning.
4. Reuse RO and hand-wash water for cleaning floors.
5. Harvest rainwater from the school roof.

How it helps the environment: less groundwater is pumped out, rainwater recharges the ground, and less electricity is used for pumping.

Sample answer — traditional rainwater harvesting techniques of India:

• Bawadi (stepwell), johad (earthen check dam) and tanka (underground tank) — Rajasthan
• Vav (stepwell) — Gujarat
• Ahar–pyne (channels and reservoir) — Bihar
• Eri (chain of village tanks) — Tamil Nadu
• Kere (village tanks) — Karnataka
• Zabo (rain caught on hilltops for terraced fields) — Nagaland

Sample findings: Elders said the air has become more dusty and smoky. People reported cough, breathlessness and watering eyes. The main local sources were smoke from vehicles, burning of garbage and crop stubble, and dust from construction.

Two practical steps: (1) a weekly “no-vehicle day” — walk, cycle or share rides to school; (2) no burning of leaves and garbage — make compost instead, and plant trees around the school.

Sample list:

Steps for the plantation drive:

1. Take permission from the Principal and fix a date (July, during Van Mahotsav).
2. Choose the places in school and suitable native trees.
3. Arrange saplings, tools, manure and tree guards.
4. Form teams, and dig the pits a day before.
5. Plant the saplings, water them, and fix tree guards and name labels.
6. Make a watering roster for the whole year.

Report: list each tree with its importance — e.g. neem (medicine, shade), amla (fruit rich in vitamin C), banyan (shade, home for birds). A sample report is in the explanation.