Water is the most precious substance on Earth. It is essential for all living things. Without water, there would be no life. Plants need water to make food, animals need water to drink, and our own bodies are made up of a large amount of water. In this chapter, we study the many roles of water and its importance in our lives.
Water is found in three states: solid, liquid, and gas. Ice is the solid state, liquid water is the state we drink, and water vapour is the gaseous state. Water changes from one state to another through processes like melting, evaporation, and condensation. These changes are part of the water cycle.
We also learn about the sources of water, how water becomes clean and safe to drink, and the importance of conserving water. Fresh water is limited, and it is our duty to save every drop. This chapter teaches us to value water as a precious resource.
Water is used for countless purposes. The main uses of water are: - For drinking: All living organisms need water to survive. - For cooking: We use water to cook food, wash vegetables, and make drinks. - For cleaning: Water is used to bathe, wash clothes, and clean our homes. - For farming: Plants and crops need water to grow. - For animals: Animals drink water and use it for their needs. - For industry: Factories use water in many manufacturing processes. - For generating electricity: Water is used in hydroelectric power stations to produce electricity. - For transportation: Ships and boats travel on water.
Around three-quarters of the Earth's surface is covered with water, yet most of it is sea water, which is salty and not fit for drinking. Only a small fraction of the Earth's water is fresh water.
Water is found in many places on Earth: - Oceans and seas: The largest bodies of water, but they are salty. - Rivers: Rivers carry fresh water from mountains and hills to the sea. - Lakes and ponds: Large and small bodies of still fresh water. - Glaciers and ice caps: Frozen fresh water found in cold regions and high mountains. - Groundwater: Water that seeps into the soil and is stored underground. We draw it out using wells and tube wells. - Atmosphere: Water exists as water vapour in the air.
Rain is the main source of fresh water on Earth. Rainwater fills rivers, lakes, and ponds, and seeps into the ground to form groundwater.
Water exists in three states: - Solid: Ice, snow, and hail are the solid forms of water. Ice is formed when water freezes at 0 degrees Celsius. - Liquid: Liquid water is what we drink. It is the most common state of water on Earth. - Gas: Water vapour is the gaseous form of water. It is invisible and present in the air.
Water changes from one state to another: - Melting: Ice to water on heating. - Freezing: Water to ice on cooling. - Evaporation: Water to water vapour on heating. - Condensation: Water vapour to water on cooling.
These changes are continuous and are driven by the heat of the Sun.
The water cycle is the continuous movement of water between the Earth and the atmosphere. It has four main stages:
The water cycle is driven by the energy of the Sun. It is also called the hydrological cycle. The water cycle ensures that water is continuously recycled on Earth.
Water can get dirty in many ways. When rain falls, it washes dirt, dust, and waste into rivers and lakes. People throw garbage, chemicals, and sewage into water bodies. Factories release chemical waste into rivers. Farmers use fertilisers and pesticides, which get washed into water. Dead animals and plants also pollute water.
Dirty water is unfit for drinking. Drinking dirty water can cause many diseases like cholera, typhoid, and diarrhoea. That is why water must be cleaned before drinking. In cities, water is cleaned in water treatment plants. In villages, water is cleaned by simple methods.
There are several methods to clean water: - Filtration: Dirty water is passed through layers of sand, gravel, and charcoal. This removes dirt and other impurities. - Boiling: Water is boiled to kill the germs present in it. Boiling is one of the simplest and most effective ways to make water safe to drink. - Adding chemicals: In water treatment plants, chemicals like chlorine are added to kill germs. - Water filters: Many homes use water filters that clean the water by removing dirt and germs. - Sedimentation: Muddy water is allowed to stand so the mud settles down, and the clean water on top is collected.
After cleaning, the water should be stored in clean containers so that it does not get dirty again.
The amount of water we need depends on many things: - Our age and body size. - The temperature of the place we live in. - The amount of physical activity we do. - The food we eat.
In hot weather, we lose a lot of water through sweat, so we need to drink more water. People doing heavy physical work, like farmers and athletes, also need more water. It is important to drink water regularly, even when we are not thirsty.
Water is precious, and we must not waste it. There are many ways to conserve water: - Turn off the tap while brushing teeth. - Fix leaking taps and pipes. - Use water carefully while bathing and washing. - Water plants in the evening or early morning to reduce evaporation. - Reuse water from washing vegetables for watering plants. - Collect rainwater for household use.
Conservation of water is important because fresh water is limited. By saving water, we help ourselves, our communities, and the environment.
If we waste water, we will face serious problems: - Rivers, lakes, and ponds will dry up. - Groundwater levels will go down. - Crops will not grow, and there will be food shortages. - Animals will not get water to drink. - People will have to walk long distances to get water. - In severe cases, there will be droughts.
Water scarcity is already a problem in many parts of the world. It is our responsibility to save water for the future. Every drop counts.
| State of Water | Example | Change Process |
|---|---|---|
| Solid | Ice, snow | Freezing (water to ice) |
| Liquid | Drinking water | Melting (ice to water) |
| Gas | Water vapour | Evaporation (water to vapour) |
| Method of Cleaning Water | How It Works |
|---|---|
| Boiling | Kills germs by heat |
| Filtration | Removes dirt through layers |
| Sedimentation | Lets mud settle down |
| Adding chlorine | Kills germs in treatment plants |
In this chapter, we learned how precious water is. Water is essential for every living thing, and it exists in three states: solid, liquid, and gas. We studied the sources of water, from oceans and rivers to glaciers and groundwater, and understood that only a small part of the Earth's water is fresh and fit for drinking. The water cycle showed us how water continuously moves between the Earth and the atmosphere through evaporation, condensation, precipitation, and collection, driven by the Sun. We learned how dirty water can make us sick and how to clean it by filtration, boiling, and chlorination. Most importantly, we understood that fresh water is limited, and conserving water is our duty. Saving every drop of water means saving life.