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Prepared by: learnloophq@gmail.com
Last edited 25 days ago by Learn LoopHQ.

Chapter: 05. Water

⁠

Section A: Multiple Choice Questions (5 Marks)

(d) 97%
© Hydrogen and Oxygen
© 0°C
© Rainwater
(b) Cholera

Section B: Fill in the Blanks (5 Marks)

H₂O
desalination
gas
solute
dehydration

Section C: True or False (5 Marks)

False
False
True
True
False

Section D: Short Answer Questions (10 Marks)

Potable water is water that is fit and safe for drinking purposes, being clean and free from germs.
Pure water is colourless, odourless, tasteless, and transparent.
Water is useful for plants as it helps in the germination of seeds and is essential for photosynthesis.
The water table is the level of groundwater, which is the reservoir of water collected over non-porous rocks below the Earth’s surface.
Stirring helps in dissolving a substance faster because it increases the contact between the solute and solvent, accelerating the mixing process.

Section E: Identifying and Differentiating Concepts (6 Marks)

Saturated Solution vs. Unsaturated Solution: A saturated solution is one where no more solute can be dissolved at a given temperature, meaning it has reached its maximum capacity. An unsaturated solution is one where more solute can still be dissolved in the solvent at that same temperature.
Dew vs. Frost: Dew consists of tiny water droplets formed when water vapour condenses on cold surfaces. Frost is formed when these tiny dew droplets, or water vapour, freeze directly onto cold objects at temperatures below 0°C.
Flood vs. Drought: A flood occurs when heavy rains cause a huge amount of water to collect and rivers to overflow, leading to submerging of land. A drought is a condition of dry weather where there is no or very little rain for a long duration, resulting in water scarcity.

Section F: Diagram-Based Question (4 Marks)

(a) The purpose of adding alum in the loading tank is to help the light suspended impurities settle down faster by making them clump together. (b) In the filtration tank, water passes through layers of sand, gravel, and charcoal. These layers act as a filter, removing the remaining lighter suspended impurities from the water.

Section G: Observation-Based Question (3 Marks)

Upon heating the tap water until it evaporates, you would observe concentric rings of some solid substances (impurities) as a residue on the watch glass.

Section H: Long Answer Questions (12 Marks)

The water cycle describes the continuous movement of water from the Earth’s surface to the atmosphere and back. It starts with evaporation, where solar heat turns liquid water into vapor, rising into the atmosphere. As the vapor rises, it cools and undergoes condensation, forming clouds of tiny water droplets. These droplets then combine and fall back to Earth as precipitation (rain, snow, or hail). This water collects in bodies like oceans, rivers, or becomes groundwater, eventually evaporating again. The water cycle is vital as it maintains the availability of freshwater on land and plays a crucial role in controlling Earth’s climatic conditions.
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* Water Cycle
** Definition: Continuous movement of water (Earth -> Atmosphere -> Earth)
** Key Steps
*** Evaporation: Solar heat, water bodies, transpiration (plants)
*** Condensation: Vapour rises, cools, forms droplets/clouds
*** Precipitation: Heavy droplets fall as rain/snow/hail
*** Collection/Flow: Water collects in bodies, groundwater, flows to oceans
** Importance
*** Maintains water on land
*** Controls climatic conditions
@endmindmap
Large-scale water purification typically occurs in a water treatment plant through several stages. First, raw water enters a sedimentation tank where large insoluble impurities settle over time. Next, it moves to a loading tank where alum is added, causing smaller suspended impurities to clump together and settle faster. Then, in the filtration tank, water passes through layers of sand, gravel, and charcoal, which effectively filter out remaining suspended particles. Finally, in the chlorination tank, bleaching powder (containing chlorine) is added to kill all disease-causing germs. The now purified and safe drinking water is then stored in large tanks before being supplied to homes.
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* Large Scale Purification of Water
** Location: Water Treatment Plant
** Input: River or Lake Water
** Steps:
*** 1. Sedimentation Tank: Large insoluble impurities settle
*** 2. Loading Tank: Alum added to settle suspended impurities faster
*** 3. Filtration Tank: Water filtered through sand, gravel, charcoal layers (removes lighter suspended impurities)
*** 4. Chlorination Tank: Bleaching powder/chlorine added to kill germs
*** 5. Storage Tank: Purified water stored for distribution to homes
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Water exhibits an anomalous behavior as it expands when cooled below 4°C, unlike most liquids that contract. This unique property means that ice, formed at 0°C, is less dense than liquid water, which is why it floats. This characteristic is crucial for aquatic life in cold regions. When lakes and rivers freeze, the ice forms an insulating layer on the surface because it is a poor conductor of heat. This insulation prevents the water beneath from freezing completely, allowing it to remain at a temperature of about 4°C, thus enabling aquatic plants and animals to survive the cold winter months.
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* Anomalous Behaviour of Water
** Normal Liquid: Contracts, density increases on cooling
** Water's Anomaly:
*** Contracts till 4°C
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