Water
Overview
A thirsty cactus, falling rain, a frozen river — all are different forms of the same thing: water. 71% of the Earth is covered with water, but drinkable water is very scarce. In this chapter, we will learn about the forms of water, the water cycle, and how to conserve water.
Typed Notes
Three Forms of Water
Water is the only naturally occurring substance on Earth that is found in all three forms: (1) Solid — ice, hail; (2) Liquid — the water we drink; (3) Gas (vapour) — which is invisible to us. With heat, solid → liquid → gas (melting, boiling); with cold, gas → liquid → solid (condensing, freezing). This constant change of form drives weather patterns and the water cycle.
The Water Cycle — Nature's Endless Journey of Water
(1) Evaporation — The Sun's heat turns water from oceans, rivers, and lakes into vapour that rises upward (plants also release water vapour through transpiration). (2) Condensation — High up in the cold air, the vapour turns into tiny water droplets — millions of these droplets together form a cloud. (3) Precipitation — The cloud becomes heavy and water falls down as rain, snow, or hail. (4) Collection — The fallen water flows into rivers and streams, and then into the ocean; some of it seeps underground to become groundwater. Then evaporation begins again — the cycle keeps going. This cycle has been running for billions of years — this is how our water keeps getting 'renewed'.
How Much Water Exists, and How Much Do We Get?
71% of the Earth's surface is covered with water — but 97% of it is in the oceans and is salty — it cannot be used for drinking or farming. Only 3% is fresh water — and most of that is locked up as ice at the poles and in glaciers. What little remains (in rivers, lakes, and groundwater) is what all humans, animals, and farms depend on. That is why drinking water is extremely precious for the world — conservation is essential.
Save Water — Every Drop Counts
(1) Turn off the tap: leaving the tap open while brushing or applying soap wastes 16 litres per minute. (2) Fix leaks immediately — one dripping tap can waste 100+ litres per day. (3) Rainwater harvesting — collect rooftop rainwater through pipes into the ground or a tank: this recharges wells and hand pumps. (4) Drip irrigation in farming — water goes directly to the roots, reducing evaporation. (5) Use water discharged from AC and RO units — for cleaning or watering plants. (6) Do not throw garbage into rivers and lakes — do not pollute fresh water. Every drop is precious — otherwise, future generations will have to fight over water.
Key Concepts
Revision ke liye ek nazar — exam se pehle yahi padhna hai.
- 01Three forms of water: solid — ice; liquid — water; gas — vapour. Heat converts water to vapour, cold converts it to ice.
- 02Water cycle: evaporation (vapour) → condensation (clouds) → precipitation (rain) → collection (rivers and oceans). The cycle never stops.
- 03Sources of water: oceans (97%, salty), rivers, lakes, rainfall, underground (wells). Only about 3% is fresh water suitable for drinking.
- 04Uses of water: drinking, farming (the largest use), household needs, factories, electricity. Shortage causes drought; excess causes floods.
- 05Conservation: turn off taps, repair leaks, rainwater harvesting, drip irrigation in farming, use water from AC/RO units for cleaning.
Questions & Solutions
Pehle khud try karo — phir solution kholo. Yahi tariqa topper banata hai.
What is the water cycle? Describe its four steps.
The ocean has so much water, yet why is drinking water scarce?
What is rainwater harvesting?
How can you save water at home? Write two methods.
How are clouds formed?
What are drought and flood?
Water has three forms — ice, liquid water, and vapour. The water cycle follows these steps: evaporation → condensation → rainfall → rivers → ocean. Ocean water is salty; drinkable fresh water is scarce. Therefore, collecting rainwater, turning off taps, and conserving water is everyone's responsibility.
Chapter-end quiz
4 MCQsOption tap karo — turant pata chalega sahi ya galat, explanation ke saath.
Q1.What is the gaseous form of water called?
Q2.What is the process of vapour turning into clouds called?
Q3.What fraction of the world's water is suitable for drinking?
Q4.What does rainwater harvesting mean?
Mark karo — dashboard par progress dikhega.