Samacheer Class 6 Science - Water

The statement 'Water present in rivers, lakes and ponds is unfit for use by human beings' is False because water from these sources is actually fit for use by human beings, though it may require treatment and purification before drinking. The statement 'Seas are formed when the water table meets the land surface' is False because seas are large bodies of salt water formed by geological processes and are not formed by the water table meeting land. The statement 'The evaporation of water takes place only in sunlight' is False because evaporation occurs from any source of heat, not just sunlight, including heat from stoves, fires, and warm air. The statement 'Condensation results in the formation of dew on grass' is True because when water vapour in the air cools down, it condenses into liquid water droplets that form dew on grass and other surfaces. The statement 'Seawater can be used for irrigation as such' is False because seawater contains high levels of salt and cannot be used directly for irrigation as it would damage crops and soil.

The heat of the sun causes evaporation of water from the surface of the earth, oceans, lakes, rivers and other water bodies.
Water vapour is also continuously added to the atmosphere through transpiration from the surface of the leaves of trees.
These droplets floating in the air along with the dust particles form clouds.
Warm air carrying clouds rises up.
Higher up in the atmosphere, the air is cool.
These vapours condense to form tiny droplets of water.
The water droplets come together to form large water droplets.
The large water droplets become heavy and the air cannot hold them, therefore, they fall as rains.

When a cooled bottle of water is taken out of the refrigerator and kept on a table, a puddle of water forms around it after some time due to the process of condensation. The cooled surface of the bottle has a temperature lower than the surrounding air. This cold surface cools the air in contact with it, reducing the temperature of the air around the bottle. When air is cooled, its capacity to hold water vapour decreases, causing the water vapour present in the air to condense into liquid water droplets. These water droplets accumulate on the outer surface of the bottle and eventually drip down to form a puddle of water on the table. This is a common example of condensation occurring in our daily life.

Aquatic animals manage to live in the Arctic and Antarctic Circle despite the extremely cold conditions because of the protective layer of ice that forms on the surface of water bodies. The floating layer of ice acts as a protective coat that insulates the water below from the extremely cold air above. This ice layer prevents heat from escaping from the water underneath, keeping the water below the ice relatively warmer than the air temperature. The water beneath the ice remains in liquid form, allowing aquatic animals such as fish, seals, and whales to survive and continue their life processes. The ice also provides protection from harsh winds and extreme cold. Additionally, aquatic animals have adapted to these cold environments through various physiological and behavioral adaptations, such as developing thick layers of fat for insulation and migrating to deeper, warmer waters when necessary.

Here are several slogans on the topic 'Save Water': 'To a thirsty man, a drop of water is worth more than a sack of gold' emphasizes the precious value of water. 'Water covers two-thirds of the surface of the earth, but only a tiny fraction is drinkable. Save water' highlights the scarcity of fresh water despite abundant water on Earth. 'Save water to secure your future' reminds us that water conservation is essential for future generations. 'Don't make nature cry, keep your water clean' encourages both water conservation and water pollution prevention. 'Store water for dry days' promotes the practice of collecting and storing water during rainy seasons for use during periods of scarcity. 'Every drop counts, don't waste water' emphasizes that even small amounts of water matter. 'Water is life, protect it' conveys the fundamental importance of water for all living beings. 'Use water wisely, live better' connects responsible water use with improved quality of life.

Although 71% of the earth's surface is covered with water, we face water scarcity because most of this water is saltwater found in oceans and seas, which is not suitable for drinking or irrigation. Only about 3% of the total water on Earth is freshwater, and even this freshwater is not always easily accessible as much of it is locked in glaciers, ice caps, and underground sources. Additionally, the demand for freshwater is increasing day by day due to growing population, industrial development, and agricultural needs. The freshwater that is available and accessible is being used faster than it can be naturally replenished through the water cycle. Furthermore, pollution and contamination of freshwater sources reduce the amount of usable water. Therefore, despite the abundance of water on Earth's surface, the scarcity of usable freshwater makes water a precious resource that needs to be conserved and managed carefully.

Sewage should not be disposed of in rivers or oceans before treatment because it contains harmful and toxic chemicals, heavy metals, and disease-causing microorganisms that can severely damage the aquatic ecosystem. When untreated sewage is released into water bodies, it pollutes the water and makes it unsafe for both aquatic life and human use. The harmful substances in sewage can kill fish and other aquatic organisms, disrupt the natural balance of the ecosystem, and reduce the oxygen levels in water, creating dead zones where life cannot survive. Additionally, untreated sewage contaminates drinking water sources and can spread waterborne diseases to humans and animals that depend on these water bodies. The toxic chemicals can accumulate in the tissues of aquatic organisms and move up the food chain, affecting larger animals and eventually humans who consume contaminated fish or other aquatic products. Therefore, sewage must be treated in sewage treatment plants to remove harmful substances before it is safely disposed of into rivers or oceans, protecting both the environment and public health.

Potable water is water that is fit and safe for drinking by human beings. It is the type of water that meets certain quality standards and does not cause any harm to health when consumed. Potable water has several important characteristics that make it suitable for drinking. It is transparent and clear, meaning it is free from visible particles and sediments that would make it appear cloudy or discolored. It is odourless, which means it does not have any unpleasant or foul smell. It is colourless, appearing as a clear liquid without any tint or discoloration. Most importantly, potable water is harmless and free from disease-causing bacteria, viruses, and other harmful microorganisms that could cause illnesses. It should also be free from toxic chemicals and heavy metals that could be dangerous to human health. Additionally, potable water should have a neutral pH and contain essential minerals in appropriate amounts that are beneficial for the human body. These characteristics ensure that potable water is safe, clean, and healthy for human consumption.

The ‘Waterman of India’ is Dr. Rajendra Singh. He is a well-known water conservationist and environmentalist from Alwar district, Rajasthan.
Awards:
He gets the Ramon Magsaysay award for community leadership in 2001.
In 2005, he got the Jamnalal Bajaj Award for Science and Technology for rural development.
In 2008, The Guardian named him amongst its list of 50 people who could save the planet.
In 2015, he won the Stockholm Water Prize. He runs an NGO called ‘Tarun Bharat Sangh’ (TBS), which was founded in 1975.
In 2016, he was bestowed with Ahimsa Award by the Institute of Jainology based in UK.

Rainwater harvesting is the direct collection and storage of rainwater for later use. It is an important method of water conservation that helps to reduce dependence on groundwater and surface water sources. There are two main types of rainwater harvesting. The first type is collecting water from where it falls, such as roof water harvesting, where rainwater is collected directly from the rooftops of houses or buildings through gutters and pipes and stored in tanks or reservoirs. The second type is collecting flowing rainwater by constructing ponds with bunds or embankments to capture and store water that flows on the ground during rainfall. In houses, rainwater harvesting can be used in several ways. The collected rainwater can be stored in underground tanks or overhead tanks and used for various household purposes such as washing clothes, cleaning floors, watering plants, and flushing toilets. If the water is properly filtered and treated, it can also be used for bathing and cooking. Rainwater harvesting reduces the burden on municipal water supply systems, helps recharge groundwater when the water percolates into the soil, and provides a sustainable source of water during dry seasons or droughts.

Yes, even when there is no pond or lake in an area, the formation of clouds will still be possible. This is because clouds form through the water cycle, which involves evaporation and transpiration from various sources. Transpiration is the process by which water is released into the atmosphere from the aerial parts of plants and trees, such as leaves and stems. When plants absorb water through their roots from the soil, this water travels up through the plant and is released as water vapor into the atmosphere through tiny pores called stomata on the leaves. This water vapor, along with water vapor from other sources like soil evaporation, rises into the atmosphere. As the water vapor rises and cools, it condenses into tiny water droplets that form clouds. Therefore, even in areas without ponds or lakes, the continuous transpiration from vegetation and evaporation from soil and other surfaces provides sufficient water vapor to the atmosphere for cloud formation. This demonstrates that the water cycle is a continuous process that does not depend solely on the presence of large water bodies.

When we breathe out on glasses to make them wet, the glasses become wet because of the process of condensation. The air we exhale from our lungs contains water vapor and is much warmer and more humid than the surrounding air. When this hot, moist air comes into contact with the cooler surface of the glasses, the temperature of the water vapor drops rapidly. As the temperature decreases, the water vapor loses energy and changes its state from gas to liquid, forming tiny water droplets on the surface of the glasses. This process is called condensation. The water droplets accumulate on the glasses, making them appear wet and creating a thin film of moisture. This moisture is useful for cleaning the glasses because it helps to loosen dust and dirt particles on the surface, allowing them to be wiped away more easily. This simple demonstration shows how condensation occurs when warm, moist air meets a cooler surface, which is the same principle that causes dew to form on grass in the early morning and water droplets to form on bathroom mirrors after a hot shower.

Based on the map of Tamil Nadu showing annual rainfall, the districts that get only low annual rainfall are located in the northwest zone and include Coimbatore, Erode, Namakkal, and Karur. The districts that get medium annual rainfall in Tamil Nadu are Pudhukottai, Virudhunagar, Sivagangai, Salem, Dindigul, Theni, and Vellore. The districts that enjoy high annual rainfall in Tamil Nadu are Tirunelveli, Kanyakumari, Chennai, Vizhupuram, Thiruvallur, Kadalur, and Nagapattinam. These variations in rainfall across different districts of Tamil Nadu are due to geographical factors such as proximity to the coast, elevation, and the direction of monsoon winds. The coastal districts and those in the eastern and southern regions receive higher rainfall, while the northwestern districts in the interior regions receive lower rainfall.