Master Chapter 11 Curiosity with comprehensive NCERT Solutions, Practice Questions, MCQs, Sample Papers, Case Based Questions, and Video lessons.
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Welcome to Chapter 11. Our journey begins with two children, Bhoomi and Surya, who are leaving the city to spend their vacation at their Ajji's (grandmother's) house. Their Ajji lives in a beautiful village on the edge of a forest in the Western Ghats.
The moment they arrive, they notice the difference. The air in the village is fresh and cooler than in the city. They are surrounded by beautiful hills, sparkling streams, and an amazing variety of plants, birds, and animals.
When they ask their Ajji to tell them about this wonderful place, she smiles and says that the village is full of "treasures of nature" that enrich our lives. She points to the pure air that is so refreshing, the fertile soil that supports so much life, the plentiful sunlight, and the many trees that provide food and shelter. Bhoomi and Surya add water to the list, which they need for drinking and for the garden.
"Without these treasures of nature," Ajji explains, "any form of life on Earth is not possible."
This chapter is a grand exploration of these essential treasures. We will follow Bhoomi, Surya, and Ajji as they investigate the air we breathe, the water we drink, the sun that gives us energy, the forests that house life, the soil under our feet, and the fuels that power our world. We are about to learn what these resources are, where they come from, and why our very survival depends on using them wisely.
Our first exploration starts with a simple act: breathing. Ajji is performing breathing exercises and asks the children to join her. As we all know from Activity 11.1, you can't hold your breath for very long. You start to feel uncomfortable. That's because our bodies need a constant supply of a gas called oxygen to survive. We can last for days without food or water, but we cannot survive for more than a few minutes without oxygen.
This vital oxygen is part of air, the invisible treasure that surrounds us. Air is not just one thing; it's a mixture of gases.
Nitrogen makes up the vast majority (about 78%).
Oxygen is the part we need to live (about 21%).
Other gases like argon, carbon dioxide, etc., make up the last 1%.
We can't see air, but we can see its effects. We see it when the leaves of a tree rustle, when clothes on a line sway, or when the pages of a book flutter. When air moves, we call it wind.
This moving air is a powerful resource. We can see this by making a simple firki (a paper pinwheel). As you run or blow on it, the wind makes it rotate. This is the exact same principle behind a giant windmill. Windmills use the energy of the wind to do useful work, like running a flour mill, pulling water from a well, or—most importantly today—generating electricity.
Next, we join Bhoomi and Surya as they help Ajji in her garden, watering the vegetables and filling the troughs for the cows. Ajji teaches them to use every drop of water with care, because, as we will discover, water is one of our most precious treasures.
We know Earth is a "blue planet." About two-thirds of its surface is covered in water. The problem is, most of that water is in oceans and seas, which means it is saline, or salty. This saline water is not fit for drinking, for growing crops, or for most industrial uses.
The water we need is freshwater. But most of this freshwater is locked away, frozen in ice sheets and snow, or hidden deep underground. The tiny, tiny fraction of freshwater that is easily accessible to us—in our ponds, rivers, lakes, and wells—is all we have.
This makes water incredibly precious, and it faces two major threats:
Wastage: We waste water in many of our daily activities, like leaving the tap running while brushing teeth, or not fixing leaky pipes.
Pollution: We pollute our limited freshwater sources by dumping trash, industrial waste, and sewage into them.
This is why Ajji's lesson is so important. We must conserve water (use it wisely) and prevent it from being polluted.
One of the most important methods of conservation is rainwater harvesting—the process of collecting and storing rainwater instead of just letting it run off. This can be done with modern systems on our rooftops, or through traditional, age-old methods like the beautiful stepwells (Bawadis) found in dry regions like Rajasthan and Gujarat.
One afternoon, the children see Ajji spreading chillies out on a mat. "We use the heat from the Sun to dry them," she explains. This simple act introduces us to the main source of energy for our entire planet.
We use the sun's heat and light for many things, like drying clothes or food. But its most important job is something we can't see directly.
Later, Bhoomi and Surya see a cow grazing. A debate begins:
Bhoomi says, "Look, the cow is eating grass and getting energy from it."
Surya says, "No, I think this cow is getting energy from the Sun."
Who is right? Ajji explains that they both are, but Surya's answer goes deeper. The cow gets energy from the grass, yes. But how did the grass get its energy? The grass used sunlight to make its own food.
This is a profound truth. The sun's energy is captured by plants, which are then eaten by animals (like the cow), which are then eaten by other animals (like us, when we drink milk). This cycle, this chain of food, is all powered by the Sun.
We also use the sun's energy in other ways. You have probably seen solar panels on rooftops or street lights. These capture the sun's energy and turn it into electricity. We can also use it directly for heating in solar water heaters or for cooking in solar cookers.
Ajji takes the children for a walk into the forest. It is a large, dense area filled with a huge variety of herbs, shrubs, and trees. Ajji explains that forests are another great treasure. They are the natural home for countless wild animals, birds, and insects, providing them with food and shelter.
Tragically, these forests are shrinking because of human activities like cutting down trees on a large scale. This is why conservation efforts are so important, from national festivals like Van Mahotsav (where new trees are planted) to famous grassroots protests like the Chipko movement, where local women in Uttarakhand hugged the trees to protect them from being cut.
While in the forest, Ajji points to the damp ground, which is covered in fallen leaves. She explains that this is an example of recycling in nature. The leaves decay, which enriches the soil with nutrients. This fertile soil is then used by new plants and trees to grow.
Soil itself is a treasure. We learn that:
Soil is formed by the breaking apart (disintegration) of rocks over thousands of years.
Rocks are made of minerals.
We use rocks and minerals for everything. We use rocks like granite and marble for building, and we extract metals like iron, copper, gold, and aluminum from minerals to make everything—from cars and airplanes to the mobile phone in your pocket.
This is a lot of treasure to keep track of: Air, Water, Sun, Forests, Soil, and Minerals. It's easy to get them all mixed up. How do we organize them? The next logical step, and one of the most important skills in science, is to classify or group them.
This is where Teachoo truly excels. We don't just give you a long list of facts; we help you build a clear mental framework to sort and understand them. Our entire approach is designed to help you see the simple, powerful patterns that connect these resources, making it easy to remember which ones last forever and which ones we must use with extreme care.
There is one last treasure to explore. As Bhoomi and Surya see cars, trucks, and buses, they learn that these vehicles run on fuels like petrol and diesel.
These fuels, alongin with natural gas and coal, are known as fossil fuels.
Formation: They are not like rocks. They were formed from the remains of microorganisms and plants that lived millions of years ago. These remains were buried deep inside the earth and, over millions of years, were converted into these fuels.
The Problem: Fossil fuels have two giant problems:
Pollution: When we burn them, they produce smoke and gases that pollute our air.
They are limited: It takes millions of years for them to form, but we are using them up incredibly fast.
This brings us to the most important concept in the entire chapter. We must classify our natural resources into two critical groups:
Renewable Resources These are the treasures that get renewed, replenished, or restored by natural processes within a reasonable amount of time.
Examples: Air, water (through the water cycle), forests (new trees can grow), and sunlight (which will not run out for billions of years).
Non-renewable Resources These are the treasures that are limited in quantity. They do not get replenished in a reasonable time. Once we use them, they are gone forever.
Examples: Fossil fuels (coal, petroleum, natural gas), minerals, rocks, and soil (which takes thousands of years to form).
The vacation ends, and Bhoomi and Surya travel back to the city. The first thing they notice is the air. It doesn't smell fresh like it did at Ajji's. They can smell the smoke from vehicles. They now understand why. The city is powered by burning non-renewable fossil fuels, polluting the renewable treasure of the air.
They have learned the most important lesson of all, best said in the words of Mahatma Gandhi: "Earth provides enough to satisfy every man's need but not for every man's greed."
To get started on this journey, click on any topic link to begin your exploration.