Water—The Essence of Life — NCERT Solutions

Given: Activity 6 showed that mustard seeds (like water) flow from higher ground to lower ground and in different directions depending on the slope.

Concept: The direction in which a river flows depends on the slope of the land.

Answer: India has a large mountain range — the Western Ghats — running along the west coast, and the Himalayas and Deccan Plateau in the north and centre. The land slopes in different directions:

• Rivers that originate in the Western Ghats flow eastward (because the land slopes towards the east) and drain into the Bay of Bengal. Example: Godavari, Krishna, Cauvery.
• Rivers that originate in the central highlands or Aravalli range flow westward (because the land slopes towards the west) and drain into the Arabian Sea. Example: Narmada, Tapti.
• The Ganga flows eastward from the Himalayas and drains into the Bay of Bengal.

Just like the mustard seeds followed the slope of the crumpled paper, rivers follow the natural slope of the land.

Given: A map of India showing rivers flowing in different directions.

Concept: Rivers flow from higher ground to lower ground. The direction depends on the slope of the land.

Note to students: Use the map provided in your textbook to trace the direction of each river and fill in the table accordingly. Rivers flowing towards the east drain into the Bay of Bengal, and rivers flowing towards the west drain into the Arabian Sea.

Given: Students visit a local water body (pond, lake, or aquarium) and observe the living beings there.

Concept: Aquatic animals have special body features (adaptations) that help them live in and around water.

Note: Fill in the table based on your own observations during the visit.

Given: Students observe plants at a water body during a visit.

Concept: Aquatic plants are of different types depending on where they grow in relation to the water.

Note: Draw the plants you actually observed during your visit and write their local names as told by your teacher or parents.

Given:

• Step 1: A drop of water is placed on plain paper.
• Step 2: Paper is coloured with wax crayon, then a drop of water is placed on it.

Concept: Plain paper absorbs water because it has tiny pores. Wax is a waterproof material — it does not allow water to pass through or be absorbed.

Observation:

• On plain paper: The drop of water is quickly absorbed into the paper. The paper becomes wet and the water spreads into it.
• On wax-crayon coloured paper: The drop of water does not get absorbed. It sits on top of the surface as a round droplet and can be easily rolled off. The paper does not get wet.

Conclusion: The wax coating makes the paper waterproof. This is similar to the waxy coating on leaves, which prevents too much water from entering the leaf and keeps the plant healthy.

Given: Four types of water and four descriptions to be matched.

Concept: Water exists in three forms — solid, liquid, and gas. Ocean water is salty and not fit for drinking. Rainwater is freshwater.

Answers:

• (i) Ocean water → (c) Not fit for drinking (because it is salty)
• (ii) Snow → (a) Solid form of water (snow and ice are the solid forms of water)
• (iii) Steam → (b) Vapour form of water (steam is water in its gaseous/vapour form)
• (iv) Rainwater → (d) Freshwater (rainwater is a source of freshwater)

Given: Most of the water on Earth exists in oceans and seas.

Concept: Water suitable for drinking and farming must be freshwater — it should have very little or no salt.

Answer: Most of the water on Earth (about 97%) is found in oceans and seas, which is saltwater. This water contains a very high amount of dissolved salts and minerals, making it unfit for drinking or irrigating crops. If we drink saltwater, it harms our body. If we use it for farming, it damages the soil and kills plants.

Only about 3% of Earth's water is freshwater, and most of that is locked in glaciers and ice caps. This means only a very tiny amount is available as liquid freshwater in rivers, lakes, and underground — which is what we use for drinking and farming.

This is why we must use freshwater carefully and not waste it.

Given: Many plants, animals, birds, and insects are found near rivers, ponds, and lakes.

Concept: Water is essential for all life processes.

Answer: A large number of living beings live near water bodies because:

1. Drinking water — All animals and birds need water to drink and survive.
2. Food — Water bodies are rich in food sources like fish, frogs, insects, and aquatic plants.
3. Habitat — Many animals like fish, frogs, crocodiles, and water birds live in or near water.
4. Breeding — Many animals lay eggs or give birth near water.
5. Plants — Aquatic plants grow in and around water, providing food and shelter to many animals.
6. Cooling — Animals use water to cool themselves in hot weather.

Thus, water bodies support a rich and diverse ecosystem of living beings.

Given: No rainfall for two years in a region.

Concept: Rain is the primary source of freshwater for rivers, lakes, ponds, and groundwater.

Answer: If it did not rain for two years, the following would happen:

1. Rivers, ponds, and lakes would dry up as they would not receive any water.
2. Groundwater levels would fall drastically as there would be no recharge.
3. Crops would fail — farmers would not be able to grow food, leading to food shortage and famine.
4. Drinking water would become very scarce, causing a severe water crisis.
5. Plants and trees would dry up and die, leading to loss of forests.
6. Animals and birds would migrate or die due to lack of water and food.
7. Soil would become dry and hard, leading to desertification (land turning into desert).
8. People would have to migrate to other areas in search of water.

In short, life would become extremely difficult and many living beings would not survive.

Given: Two different environments — a forest and a city — receiving the same rainfall.

Concept: The surface type determines how rainwater is absorbed, stored, or lost.

In a Forest:

• Trees and plants slow down the falling rain, so it does not hit the ground with full force.
• The soil in a forest is soft, loose, and rich in organic matter, so it absorbs rainwater easily.
• Water slowly seeps deep into the ground, recharging groundwater.
• Tree roots hold the soil together, preventing erosion.
• Some water is absorbed by plant roots and released back into the air through leaves (transpiration).
• Rivers and streams in forests flow steadily throughout the year.

In a City:

• Most surfaces are covered with concrete, tar roads, and paved areas that do not absorb water.
• Rainwater flows away quickly as runoff into drains and eventually into rivers or the sea.
• Very little water seeps into the ground, so groundwater is not recharged.
• This can cause flooding during heavy rains because water has nowhere to go.
• Water is wasted instead of being stored.

Conclusion: Forests help conserve rainwater and recharge groundwater, while cities lose most rainwater as runoff.

Given: We need to design a water-conserving house or school.

Concept: Water conservation means using water carefully and finding ways to collect, reuse, and reduce wastage of water.

My Design for a Water-Conserving School/House would include:

1. Rainwater Harvesting System — Pipes on the roof to collect rainwater and store it in a large underground tank for later use.
2. Soak Pit — A pit in the garden where water can seep into the ground to recharge groundwater.
3. Garden with Native Plants — Plants that need less water, so less water is used for gardening.
4. Drip Irrigation — For the garden, so water goes directly to plant roots without wastage.
5. Low-flow Taps and Flush Tanks — Taps and toilets that use less water.
6. Greywater Recycling — Water used for washing hands or dishes can be reused to water plants.
7. No Concrete in the Compound — Keeping some open, unpaved areas so rainwater can seep into the ground.
8. Leakage Check System — Regular checking of pipes and taps to prevent leaks.
9. Awareness Boards — Reminders to turn off taps when not in use.

Conclusion: A water-wise house or school saves water, reduces wastage, and helps recharge groundwater for future use.

Given: Step-by-step images (Steps 1–6) for making a paper fish using origami.

This is a hands-on craft activity. Follow the steps shown in the images in your textbook:

• Step 1: Take a square piece of paper.
• Step 2: Fold it diagonally to make a triangle.
• Step 3: Fold it again to make a smaller triangle.
• Step 4: Open one flap and press it flat to make a square shape.
• Step 5: Fold the sides to shape the body and tail of the fish.
• Step 6: Your paper fish is ready! You can draw an eye and colour it.

Note: Follow the exact folding steps shown in the images in your textbook. This activity helps us appreciate the fish — an important aquatic animal that lives in freshwater bodies and is part of the water ecosystem we studied in this chapter.