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Earth—Our Shared Home - The Blue Planet: Earth as Our Home

Grade 5CBSE

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

🔑Concepts

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Earth is the 3rd3^{rd} planet from the Sun and the only known planet in the solar system to support life.

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It is called the 'Blue Planet' because approximately 71%71\% of its surface is covered by water.

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The atmosphere is a protective blanket of gases (mainly Nitrogen and Oxygen) that traps heat and blocks harmful ultraviolet (UV) radiation.

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The presence of liquid water, an breathable atmosphere, and an ideal temperature (the 'Goldilocks Zone') makes life possible.

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Earth performs two types of movements: Rotation (on its axis) causing day and night, and Revolution (around the Sun) causing seasons.

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The Earth is slightly tilted on its axis at an angle of 23.5∘23.5^\circ.

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The Lithosphere (land), Hydrosphere (water), and Atmosphere (air) meet at the Biosphere where life exists.

📐Formulae

Surface Composition=71% Water+29% Land\text{Surface Composition} = 71\% \text{ Water} + 29\% \text{ Land}

Atmospheric Air≈78% Nitrogen+21% Oxygen+1% Other Gases (CO2, Argon, etc.)\text{Atmospheric Air} \approx 78\% \text{ Nitrogen} + 21\% \text{ Oxygen} + 1\% \text{ Other Gases (CO}_2, \text{ Argon, etc.)}

1 Rotation=24 hours\text{1 Rotation} = 24 \text{ hours}

1 Revolution=36514 days\text{1 Revolution} = 365 \frac{1}{4} \text{ days}

Average Distance from Sun≈1.5×108 km\text{Average Distance from Sun} \approx 1.5 \times 10^8 \text{ km}

💡Examples

Problem 1:

If a leap year occurs every 44 years to account for the extra 14\frac{1}{4} day in the revolution period, how many total days are there in a period of 44 years?

Solution:

365+365+365+366=1461 days365 + 365 + 365 + 366 = 1461 \text{ days}

Explanation:

Three normal years have 365365 days each, and every fourth year (leap year) has 366366 days to accommodate the sum of the four 14\frac{1}{4} days (0.25×4=10.25 \times 4 = 1 full day).

Problem 2:

Calculate the approximate ratio of water to land on Earth's surface.

Solution:

Ratio≈71:29≈7:3\text{Ratio} \approx 71 : 29 \approx 7 : 3

Explanation:

Since water covers about 71%71\% and land covers 29%29\%, the ratio is roughly 77 parts water to 33 parts land.

Problem 3:

A scientist is studying the atmosphere. If she collects 100100 liters of pure dry air, approximately how many liters of Oxygen will it contain?

Solution:

100×21100=21 liters100 \times \frac{21}{100} = 21 \text{ liters}

Explanation:

Oxygen makes up approximately 21%21\% of the Earth's atmosphere by volume.