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Air and Atmosphere - Greenhouse Effect and Global Warming

Grade 7ICSE

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

🔑Concepts

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The Greenhouse Effect is a natural process where certain gases in the Earth's atmosphere trap heat, preventing it from escaping into space, thereby keeping the planet warm enough to sustain life. Without this, the average temperature would be around −18∘C-18^\circ C.

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Greenhouse Gases (GHGs) are those that contribute to the greenhouse effect. The primary GHGs include Carbon Dioxide (CO2CO_2), Methane (CH4CH_4), Nitrous Oxide (N2ON_2O), Water Vapor (H2OH_2O), and Chlorofluorocarbons (CFCsCFCs).

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Global Warming is the observed century-scale rise in the average temperature of the Earth's climate system due to the enhanced greenhouse effect caused by human activities such as burning fossil fuels and deforestation.

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Deforestation leads to an increase in CO2CO_2 levels because trees that perform photosynthesis (6CO2+6H2O→C6H12O6+6O26CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2) are removed, reducing the amount of CO2CO_2 absorbed from the atmosphere.

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Impacts of Global Warming include the melting of polar ice caps, rising sea levels, extreme weather patterns, and loss of biodiversity.

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The Ozone layer (O3O_3) in the stratosphere protects the Earth from harmful Ultraviolet (UVUV) radiation, but ground-level ozone can act as a greenhouse gas.

📐Formulae

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

CH4+2O2→CO2+2H2O+HeatCH_4 + 2O_2 \rightarrow CO_2 + 2H_2O + \text{Heat}

C+O2→CO2C + O_2 \rightarrow CO_2

💡Examples

Problem 1:

Explain why an increase in the concentration of CO2CO_2 from 0.03%0.03\% to higher levels is a concern for environmentalists.

Solution:

An increase in CO2CO_2 concentration leads to an enhanced greenhouse effect.

Explanation:

Carbon dioxide (CO2CO_2) molecules have the property of trapping infrared radiation (heat) reflected from the Earth's surface. As the concentration increases beyond its natural level (approx. 0.03%0.03\%), more heat is trapped in the atmosphere, leading to a rise in global temperatures known as Global Warming.

Problem 2:

Calculate the number of oxygen atoms in 3 molecules of Carbon Dioxide (CO2CO_2).

Solution:

3×2=63 \times 2 = 6 oxygen atoms.

Explanation:

Each molecule of CO2CO_2 contains 22 atoms of Oxygen (OO). Therefore, 33 molecules of CO2CO_2 contain 3×2=63 \times 2 = 6 atoms of Oxygen.

Problem 3:

Identify the gas 'X' in the reaction: CH4+2O2→X+2H2OCH_4 + 2O_2 \rightarrow X + 2H_2O. How does this gas affect the atmospheric temperature?

Solution:

The gas 'X' is CO2CO_2.

Explanation:

The combustion of Methane (CH4CH_4) produces Carbon Dioxide (CO2CO_2) and Water Vapor. CO2CO_2 is a greenhouse gas that absorbs long-wave terrestrial radiation, causing the atmospheric temperature to increase.