Water—The Essence of Life

Given: Ocean water makes up the majority of water on Earth.

Concept: Ocean water is saltwater — it contains a very high amount of dissolved salts and minerals.

Answer: No, we cannot drink ocean water directly. It is too salty for human consumption. If we drink it, it would actually make us more thirsty and could harm our kidneys. Ocean water needs to be treated (desalinated) to remove the salt before it can be used for drinking.

Given: Ocean water is salty and not fit for drinking directly.

Concept: Even though ocean water cannot be drunk directly, it has several other uses.

Answer: Ocean water can be used for:
1. Producing salt — Seawater is dried in salt pans (like those in Gujarat) to collect salt.
2. Navigation and transport — Ships and boats travel across oceans to carry goods and people.
3. Fishing — Many fish and seafood are found in the ocean.
4. Desalination — With special treatment, ocean water can be converted into drinking water.
5. Recreation — Swimming, surfing, and other water sports.
6. Generating energy — Tidal energy can be produced using ocean waves.

Given: Various images showing different sources of water in nature.

Concept: Freshwater is water that contains very little or no salt. It is found in several natural and man-made sources.

The freshwater sources that can be identified from the images are:
1. River — Flowing water on land that originates from mountains or rainfall.
2. Lake — A large body of still freshwater surrounded by land.
3. Pond — A small, shallow body of still freshwater.
4. Glacier / Snow-capped mountains — Frozen freshwater stored as ice and snow.
5. Waterfall — Freshwater falling from a height.
6. Well / Borewell — Underground freshwater accessed by digging.
7. Rainwater — Freshwater that falls directly from clouds.
8. Stream — A small, narrow flowing body of freshwater.
9. Groundwater / Handpump — Water stored underground, drawn up for use.

Conclusion: Freshwater is found in rivers, lakes, ponds, glaciers, groundwater, and as rainwater.

Given: A steel glass is filled with ice cubes. Small water droplets form on the outside of the glass.

Concept: The air around us contains water vapour (water in gaseous form). When this warm, moist air comes in contact with the cold surface of the glass, it cools down. The water vapour in the air condenses (changes from gas to liquid) and forms tiny water droplets on the outer surface of the glass.

Answer: The water droplets come from the water vapour present in the surrounding air. The cold glass causes the water vapour to condense into liquid water droplets on its surface. This process is called condensation.

Given: Ice cubes are placed in a steel glass and left for some time.

Concept: Ice is the solid form of water. When ice is kept at room temperature, it absorbs heat from the surroundings.

Answer: The ice cubes slowly melt and turn into liquid water. This is because the warmth of the room provides heat energy to the ice, causing it to change from solid form to liquid form. This process is called melting.

Given: Water is heated.

Concept: When water is given heat energy, its temperature rises. At 100°C, water boils and converts into steam (water vapour).

Answer: When we heat water, it first becomes warm, then it starts to boil and converts into steam (water vapour). This process is called evaporation (or vaporisation). The water changes from its liquid form to its gaseous form (vapour/steam).

Given: Three activities involving water in different conditions.

Concept: Water can exist in three forms — solid (ice), liquid (water), and gas (vapour/steam). It changes form when heat is added or removed.

| Activity | I Observe |
|---|---|
| Ice melting | The ice slowly turns into liquid water. The solid form changes to liquid form. This is called melting. |
| Water boiling | Bubbles form in the water and steam (water vapour) rises up. The liquid form changes to gaseous form. This is called boiling/evaporation. |
| Water in sunlight for three days | The level of water in the container gradually decreases and eventually the water disappears. The water slowly evaporates into the air as water vapour due to the heat of the sun. |

Forms of water seen in Activity 2: Solid (ice), Liquid (water), and Gas (steam/vapour).

Given: A transparent bag filled one-third with coloured water is sealed and placed in sunlight. Observations are to be recorded.

Concept: This activity demonstrates the water cycle — evaporation, condensation, and precipitation.

| I Observe | I Wonder | It is because of... |
|---|---|---|
| Water heats up | How does water heat up? | Sunlight (solar energy heats the water) |
| Water droplets formed inside the cover | How did water get to the top of the bag? | Evaporation — water turned into vapour due to heat, rose up, and condensed on the cooler surface of the bag |
| Water droplets fall back down / drip to the bottom | Why do the droplets fall down? | Gravity — when droplets become heavy enough, they fall back down, just like rain |

Conclusion: This activity shows the complete water cycle — the sun heats water (evaporation), water vapour rises and cools to form droplets (condensation), and droplets fall back down (precipitation/rain).

Given: Three surfaces — concrete road, green lawn, and paved area.

Concept: Groundwater recharge happens when rainwater seeps through the soil and goes deep underground. Hard, cemented surfaces do not allow water to pass through them.

Answer: ✅ Green lawn will help in groundwater recharge.

Reason: A green lawn has soil and grass, which allows rainwater to slowly seep through the ground and reach underground water reserves. Concrete roads and paved areas are hard surfaces that do not allow water to pass through, so rainwater flows away as runoff and cannot recharge groundwater.

Given: Mustard seeds are poured from the highest point of a crumpled newspaper slope.

Observation: The mustard seeds flow downward from the highest point towards the lower areas of the slope. They do not stay at the top but move along the folds and slopes of the paper.

Given: Mustard seeds are poured on a crumpled newspaper with uneven slopes.

Observation: The mustard seeds do not move in a straight line. They spread out in different directions depending on the shape of the slopes and folds in the paper. They follow the path of least resistance, just like water flows along the natural shape of the land.

Given: Mustard seeds flow over a crumpled newspaper surface.

Observation: Yes, the mustard seeds collect in the lower, hollow areas of the crumpled paper. They gather in the depressions and valleys, just like water collects in low-lying areas to form lakes, ponds, and rivers.

Conclusion: This activity shows us that water (like the mustard seeds) always flows from higher ground to lower ground. The shape of the land determines the direction in which rivers flow. Some rivers flow towards the Bay of Bengal (east) and some towards the Arabian Sea (west) depending on the slope of the land they travel over.