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Water and Life - Importance and Uses of Water

Grade 6CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Water is an essential natural resource for all living organisms, represented by the chemical formula H2OH_2O.

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About 71%71\% of the Earth's surface is covered with water, but only a very small fraction (approx. 2.5%2.5\%) is fresh water suitable for human consumption.

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Water exists in three states: Solid (ice), Liquid (water), and Gas (water vapor). These states are interconvertible through heating or cooling.

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The Water Cycle consists of key processes: Evaporation (liquid to vapor), Transpiration (loss of water from plants), Condensation (vapor to liquid), and Precipitation (rain, snow, or hail).

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Groundwater is a significant source of fresh water, which is accessed through wells and hand pumps. The upper limit of this underground water is known as the Water Table.

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Conservation of water is necessary due to increasing demand. Methods include Rainwater Harvesting, where rainwater is collected and stored or allowed to seep into the ground to recharge the groundwater.

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Excessive rainfall leads to 'Floods', while a lack of rain over a long period in a particular area leads to 'Droughts'.

📐Formulae

H2OH_2O

Total Water on Earth≈97% (Saline)+3% (Fresh water)\text{Total Water on Earth} \approx 97\% \text{ (Saline)} + 3\% \text{ (Fresh water)}

Ice⇌CoolingHeatingWater⇌CoolingHeatingWater Vapor\text{Ice} \xrightleftharpoons[\text{Cooling}]{\text{Heating}} \text{Water} \xrightleftharpoons[\text{Cooling}]{\text{Heating}} \text{Water Vapor}

6CO2+6H2O→SunlightC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{Sunlight}} C_6H_{12}O_6 + 6O_2

💡Examples

Problem 1:

If a small village requires 50,00050,000 liters of water per day and the population is 500500 people, calculate the average water consumption per person in one day.

Solution:

Average consumption =50,000500=100= \frac{50,000}{500} = 100 liters per person.

Explanation:

To find the per capita consumption, we divide the total water consumed by the total number of people in the village.

Problem 2:

Explain why H2OH_2O is considered a universal solvent.

Solution:

Water is called a universal solvent because it can dissolve more substances than any other liquid.

Explanation:

Due to its chemical polarity, H2OH_2O molecules can attract and break down various solutes, which is vital for transporting nutrients and minerals in living organisms.

Problem 3:

A glass of cold water shows droplets on its outer surface. Identify the process involved.

Solution:

The process is called Condensation.

Explanation:

Water vapor present in the air comes in contact with the cold surface of the glass, loses heat energy, and converts back into liquid water droplets.