Long Answers

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Last edited 25 days ago by Learn LoopHQ.

Chapter: 05. Water

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Explain the distribution of water on Earth and its presence in different forms.

Two-thirds of Earth’s surface is covered with water. About 97% of this is saline water found in seas and oceans, which is not suitable for consumption. Another 2% exists as frozen glaciers and polar ice caps. Only a small fraction, 1%, is available as freshwater in rivers, lakes, ponds, and groundwater. Additionally, water is present as vapour, mist, and clouds in the atmosphere, and remarkably, about 70% of the human body is also composed of water.

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Describe the properties of pure water and its three states of existence.

Pure water is a colourless, odourless, and tasteless transparent liquid. It has a specific boiling point of 100°C, at which it transforms into water vapour, and a freezing point of 0°C, where it becomes ice. Water exists naturally in three states: solid, found as ice or snow; liquid, as seen in oceans, rivers, and rain; and gaseous, present as water vapour in the air. These states can interconvert with changes in temperature, which is a fundamental aspect of the water cycle.

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Explain the water cycle, detailing its key steps and importance.

The water cycle describes the continuous movement of water from the Earth’s surface to the atmosphere and back. It begins with evaporation, where solar heat transforms water from bodies like oceans into vapour, along with transpiration from plants. This vapour rises, cools, and undergoes condensation to form tiny water droplets, creating clouds. When these droplets become heavy, they fall back as precipitation (rain, snow, or hail). This water then collects in bodies or seeps into the ground, eventually returning to oceans, ready to evaporate again. The water cycle is vital for maintaining water levels on land and controlling climatic conditions globally.

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Describe the anomalous behavior of water and its crucial role in sustaining aquatic life in cold regions.

Unlike most liquids that continuously contract and become denser upon cooling, water exhibits anomalous expansion. It contracts normally until 4°C, but upon further cooling below 4°C, it begins expanding until it freezes at 0°C. This unique property makes ice less dense than liquid water, causing it to float on the surface. This behavior is crucial for aquatic life in cold regions; during winter, the ice layer on lakes acts as an insulator. This insulation prevents the water below from freezing completely, allowing the deeper water to remain at 4°C, which enables aquatic plants and animals to survive.

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What are water-borne diseases? Name some and explain why drinking purified water is essential.

Water-borne diseases are illnesses caused by consuming water contaminated with harmful microorganisms like bacteria and viruses. Common examples include cholera, diarrhoea, gastroenteritis, dysentery, hepatitis, jaundice, and typhoid. These diseases can cause severe symptoms such as acute diarrhoea, vomiting, and inflammation, often leading to dehydration, which can be fatal if untreated. Therefore, drinking purified water is essential to eliminate these disease-causing germs and impurities, safeguarding public health and preventing the spread of such ailments.

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Elaborate on the large-scale purification process of water in a treatment plant.

Large-scale water purification typically occurs in a water treatment plant, starting with raw water from rivers or lakes. First, in a sedimentation tank, large insoluble impurities settle at the bottom. Then, in a loading tank, alum is added to accelerate the settling of smaller suspended impurities. The water then moves to a filtration tank, passing through layers of sand, gravel, and charcoal to remove finer suspended particles. Next, in the chlorination tank, bleaching powder (chlorine) is added to kill all remaining germs, making the water safe for consumption. Finally, the purified water is stored in large storage tanks before being distributed to homes via pipes.

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Discuss various methods for conserving water.

Water conservation is crucial due to the limited availability of freshwater. Several methods can be employed, starting with simple actions like closing taps immediately after use and repairing leaks promptly. Preventing overflow of overhead tanks and reusing water, such as collecting vegetable washing water for plants, are effective strategies. Implementing rainwater harvesting, including rooftop systems where collected rainwater recharges groundwater, is vital. Encouraging efficient irrigation techniques like drip and sprinkle methods reduces agricultural water waste. Lastly, treating and reusing domestic wastewater for industrial and agricultural purposes, along with planting trees, and constructing reservoirs and dams, all contribute significantly to water conservation.

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