Welcome to Class 10 Chemistry Chapter 14 – Environmental Chemistry!
This chapter explains the Earth’s atmosphere, its composition, layers, and the effects of human activities on air quality and the environment. You will also learn about pollutants, acid rain, and ozone depletion, and how they impact life and nature.
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Composition of Atmosphere: Understand the gases surrounding Earth and their role in supporting life.
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Layers of Atmosphere: Learn about the different atmospheric layers and their importance in protecting the Earth.
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Pollutants: Discover the sources of air pollution and their harmful effects on humans, plants, and animals.
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Acid Rain and Its Effects: Study how acid rain forms and its damaging effects on buildings, crops, and ecosystems.
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Ozone Depletion and Its Effects: Learn why the ozone layer is important, how it is depleted, and the consequences for life on Earth.
These notes are designed for easy revision and exam preparation, including MCQs, short questions, and long questions.
Important MCQs – Chapter 14 Environmental Chemistry
1. Which layer of the atmosphere lies just above the Earth’s surface?
(a) Stratosphere
(b) Troposphere ✅
(c) Mesosphere
(d) Thermosphere
2. Which atmospheric layer contains the ozone layer?
(a) Troposphere
(b) Mesosphere
(c) Thermosphere
(d) Stratosphere ✅
3. What is the atmosphere?
(a) A solid cover around Earth
(b) Envelope of gases around Earth ✅
(c) A layer of magnetic field
(d) Mixture of liquids
4. What percentage of the atmospheric mass is found within the first 30 km from Earth’s surface?
(a) 90%
(b) 80%
(c) 99% ✅
(d) 70%
5. Which of the following is not a primary air pollutant?
(a) Carbon monoxide (CO)
(b) Sulphur dioxide (SO₂)
(c) Nitric oxide (NO)
(d) Ozone (O₃) ✅
Short Questions – Chapter 14 Environmental Chemistry
1. State the major sources of CO and CO₂ emission.
Answer:
Major Sources:
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Combustion engines of vehicles (petrol and diesel)
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Burning of fossil fuels such as coal, oil, and natural gas
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Open-air fires and industrial kilns
These activities release both CO (Carbon Monoxide) and CO₂ (Carbon Dioxide) into the atmosphere, contributing to air pollution and global warmi
2. How is ozone layer formed in the stratosphere?
Answer:
Formation of Ozone:
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Step 1: Oxygen molecules (O₂) absorb ultraviolet (UV) rays and split into oxygen atoms (O).
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Step 2: These oxygen atoms (O) react with oxygen molecules (O₂) to form ozone (O₃).
Reaction: 🧪
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O₂ + UV ⇒ O + O
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O + O₂ ⇒ O₃ (ozone)
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This continuous process creates and maintains the ozone layer in the stratosphere, which protects Earth from harmful UV radiation.
3. Why does 75% of the atmospheric mass lie within the troposphere?
Answer:
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Gravity pulls most gases toward the Earth’s surface.
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The troposphere is the lowest layer of the atmosphere, so it contains denser air.
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Therefore, approximately 75% of the atmospheric mass is concentrated in the troposphere.
Explanation:
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This is why weather phenomena, clouds, and most living organisms are found in the troposphere.
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The higher layers contain thinner air and less mass.
4. What do you mean by an air pollutant?
Answer:
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An air pollutant is any unwanted or harmful substance present in the air that can damage human health, the environment, or the climate.
Examples of air pollutants:
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Carbon monoxide (CO)
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Sulphur dioxide (SO₂)
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Nitrogen oxides (NOx)
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Smoke
Explanation:
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Air pollutants can be gases, particles, or biological molecules.
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They are responsible for respiratory problems, environmental degradation, acid rain, and climate change.
Long Questions – Chapter 14 Environmental Chemistry
Q1: Write down the significance of atmospheric gases.
Introduction:
The atmosphere is the thin layer of gases that surrounds the Earth. These gases are essential for life as they protect us from harmful solar radiation, regulate the Earth’s temperature, and support various biological and chemical processes necessary for living organisms.
Major Atmospheric Gases & Their Significance
1. Nitrogen (N₂) – 78%
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Nitrogen is an inert gas, which means it does not easily react with other substances.
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It dilutes oxygen in the air, preventing rapid burning and explosions.
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Nitrogen is a key component of the nitrogen cycle, which is essential for plant growth and soil fertility.
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2. Oxygen (O₂) – 21%
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Oxygen is essential for respiration in humans, animals, and some microorganisms.
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It supports combustion, allowing fuels to burn efficiently for energy.
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Oxygen is vital for metabolic reactions in cells that produce energy.
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3. Carbon Dioxide (CO₂) – 0.03%
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Plants use CO₂ during photosynthesis to make glucose, which is the primary energy source for most living organisms.
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CO₂ contributes to the greenhouse effect, helping maintain Earth’s temperature suitable for life.
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It plays a significant role in the carbon cycle, recycling carbon through ecosystems.
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4. Water Vapour (H₂O)
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Water vapour is essential for cloud formation and rainfall, which sustains life on Earth.
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It helps in regulating temperature through evaporation and condensation.
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Water vapour also carries heat energy around the planet, influencing weather patterns.
5. Ozone (O₃)
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Found in the stratosphere, forming the ozone layer.
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Absorbs harmful ultraviolet (UV) rays from the sun, protecting humans, animals, and plants from radiation damage.
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Without ozone, life on Earth would face severe health risks like skin cancer and cataracts.
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Other Trace Gases
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Methane (CH₄), Nitrous oxide (N₂O), Argon (Ar)
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These gases, although present in small amounts, contribute to climate regulation and participate in chemical reactions in the atmosphere.
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Summary:
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Atmospheric gases are vital for sustaining life on Earth.
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They regulate climate, protect against harmful radiation, support plant growth, and enable respiration and energy production.
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Maintaining the balance of these gases is essential, as any significant change can disrupt ecosystems and make the Earth uninhabitable.
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