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Our Home: Earth, a Unique Life Sustaining Planet - Air, water, and sunlight

Grade 8CBSE

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

🔑Concepts

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Earth is the only known planet in our solar system to support life due to its ideal distance from the Sun, creating a 'Goldilocks Zone' with suitable temperatures.

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The atmosphere is a mixture of gases: approximately 78%78\% Nitrogen (N2N_2), 21%21\% Oxygen (O2O_2), and 0.03−0.04%0.03-0.04\% Carbon Dioxide (CO2CO_2).

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The Ozone Layer (O3O_3), located in the stratosphere, protects life by absorbing harmful Ultraviolet (UV) radiation from the Sun.

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The Greenhouse Effect is the process by which gases like CO2CO_2 and methane (CH4CH_4) trap heat in the atmosphere, keeping Earth warm enough for life.

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Water covers about 71%71\% of the Earth's surface, acting as a universal solvent and a vital medium for biochemical reactions in living organisms.

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Sunlight is the primary source of energy. Plants convert solar energy into chemical energy through photosynthesis: 6CO2+6H2O→C6H12O6+6O26CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2.

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The Water Cycle involves continuous movement of water through evaporation, condensation, and precipitation, powered by heat from the Sun.

📐Formulae

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

Pressure(P)=Force(F)Area(A)\text{Pressure} (P) = \frac{\text{Force} (F)}{\text{Area} (A)}

Oxygen Content=Total Volume of Air×21100\text{Oxygen Content} = \text{Total Volume of Air} \times \frac{21}{100}

💡Examples

Problem 1:

If a sample of air has a total volume of 500 L500 \text{ L}, calculate the approximate volume of Oxygen present in it.

Solution:

VO2=500×21100=105 LV_{O_2} = 500 \times \frac{21}{100} = 105 \text{ L}

Explanation:

Since Oxygen makes up approximately 21%21\% of the Earth's atmosphere, we multiply the total volume by 0.210.21.

Problem 2:

Calculate the difference in atmospheric pressure if the pressure at sea level is 101325 Pa101325 \text{ Pa} and the pressure at a specific mountain peak is 89450 Pa89450 \text{ Pa}.

Solution:

101325−8945011875\begin{array}{r} 101325 \\ -89450 \\ \hline 11875 \end{array}

Explanation:

The difference in pressure is calculated by subtracting the higher altitude pressure from the sea level pressure, resulting in 11875 Pa11875 \text{ Pa}.

Problem 3:

Explain why life cannot exist without the Sun using the concept of energy flow.

Solution:

Sunlight →\rightarrow Producers (Plants) →\rightarrow Consumers (Animals).

Explanation:

The Sun provides energy for photosynthesis. Without sunlight, plants cannot produce glucose (C6H12O6C_6H_{12}O_6), leading to a collapse of the entire food chain.