Composition and Structure Of The Atmosphere

Our planet is enveloped by the atmosphere, a combination of gases where nitrogen and oxygen are most abundant, accompanied by varying levels of water in gaseous form and minute solid or liquid specks. This blend is essential for sustaining life and driving the Earth’s weather systems.

This atmospheric blanket isn’t the same all the way up; it’s structured into distinct layers defined by how temperature changes with altitude. The troposphere, closest to the ground, is where most of our weather occurs. Above it lies the stratosphere, which contains the vital ozone layer that protects us from the sun’s harmful rays. Ascending further, the mesosphere is a very cold layer where meteors typically burn up. Comprehending this composition and layered structure is key to understanding weather, climate, and the atmosphere’s protective role for Earth.

Discuss

Question
Discuss the importance of the different layers of the atmosphere ?
Ans:

The various layers of Earth’s atmosphere each perform an essential and distinct role in sustaining our planet. The troposphere, where we live, is the site of all weather phenomena and the distribution of heat. The stratosphere contains the crucial ozone layer, which absorbs damaging ultraviolet rays from the sun. The mesosphere serves as a protective barrier, incinerating most meteors that enter Earth’s atmosphere. The thermosphere, despite its high temperatures, holds the ionosphere, which is vital for long-range radio communication and the occurrence of auroras. Lastly, the exosphere forms the boundary with outer space and is the orbital home for numerous important satellites. These interconnected layers collaborate to make and keep Earth a place where life can thrive.

THINK AND ANSWER

Question
What would happen to the earth if the atmosphere disappeared ?
Ans:

If the Earth’s atmosphere suddenly disappeared, the consequences would be catastrophic and would render the planet utterly inhospitable to all known forms of life. Here’s a breakdown of what would happen:  

• Loss of Breathable Air: The most immediate and obvious impact would be the lack of oxygen for humans and most other terrestrial animals to breathe. Suffocation would occur within minutes.  
• No Air Pressure: The atmosphere exerts a significant amount of pressure. Without it, our bodily fluids would boil at normal body temperature. This would lead to immediate and gruesome death for any unprotected life.  
• Extreme Temperature Fluctuations: The atmosphere acts as a blanket, trapping some of the Sun’s heat and distributing it around the globe. It also helps to moderate temperature differences between day and night. Without it:
  • Daytime temperatures would soar to scorching levels, as there would be no atmosphere to filter the intense solar radiation.  
  • Nighttime temperatures would plummet to extremely frigid levels, as there would be no atmosphere to retain heat. These extreme temperature swings would make survival impossible.  
• No Protection from Radiation: The atmosphere, particularly the ozone layer in the stratosphere, shields us from harmful ultraviolet (UV) radiation and other forms of solar and cosmic radiation. Without this protection, all life would be exposed to lethal levels of radiation, leading to widespread death and genetic damage.  
• Constant Meteorite Bombardment: The atmosphere causes most small to medium-sized meteors to burn up due to friction before they reach the surface. Without this protective layer, Earth would be constantly bombarded by meteoroids, posing a significant threat to any remaining structures or life.
  
• No Sound Transmission: Sound waves require a medium to travel through. In the vacuum of space, there is no sound. Without an atmosphere, there would be complete silence.  
• Loss of Water: The atmosphere plays a crucial role in the water cycle, facilitating evaporation, cloud formation, and precipitation. Without it, liquid water on the surface would likely evaporate quickly into space, and the water cycle would cease to exist.

VALUES AND LIFE SKILLS

Question
We often leave the lights switched on and fans running when we are not in the room. We switch on the air-conditioning even though we don’t really need it. We insist on being dropped to school in the car every day. Thus, we waste valuable energy which is generally produced by burning coal and petroleum. As you know, the burning of these fuels release gases that pollute the atmosphere.
Make a list of the similar things that we do without realizing that we are destroying the environment. Think of the ways that we can behave differently.
Ans:

You’ve highlighted some very common and impactful ways we unknowingly harm the environment in our daily routines. Here’s a list of similar things we do without realizing their negative consequences, along with suggestions for different behaviors:

Unrealized Environmentally Damaging Actions:

• Excessive Water Usage:
  • Leaving taps running while brushing teeth, washing dishes, or shaving.
  • Taking long showers or baths.
  • Watering lawns excessively or during the hottest part of the day when much of it evaporates.
  • Using a washing machine or dishwasher for small loads.
• Wasteful Consumption and Disposal:
  • Using and discarding single-use plastics (bags, bottles, cutlery, straws) without considering alternatives.
  • Not separating waste for recycling and composting, leading to more landfill burden.
  • Buying excessively and contributing to demand for resource-intensive production.
  • Discarding clothes, electronics, and other items that could be repaired, reused, or donated.
• Food-Related Waste and Choices:
  • Wasting food by taking more than we can eat or not storing it properly.
  • Consuming large amounts of meat, which has a higher carbon footprint than plant-based foods due to land use, animal agriculture emissions, and water consumption.
  • Buying food that has traveled long distances, increasing transportation emissions.
• Transportation Habits:
  • Opting for personal vehicles for short distances instead of walking, cycling, or using public transport.
  • Not carpooling when multiple people are going to the same place.
  • Driving inefficiently (e.g., rapid acceleration and braking).
  • Flying frequently for short trips where alternatives exist.
• Energy Consumption Beyond Necessity:
  • Leaving electronic devices plugged in even when fully charged (phantom load).
  • Using energy-intensive appliances during peak hours.
  • Not insulating homes properly, leading to increased heating and cooling needs.
  • Over-lighting rooms or outdoor areas.
• Use of Harmful Chemicals:
  • Using excessive amounts of chemical cleaners, pesticides, and fertilizers that can pollute water and soil.
  • Not disposing of hazardous waste (batteries, electronics, paints) properly.
• Disregard for Nature:
  • Littering in natural environments.
  • Supporting activities that harm wildlife or destroy habitats (e.g., purchasing products made from endangered species).
  • Not respecting local ecosystems during outdoor activities.

Ways to Behave Differently (Sustainable Alternatives):

• Conscious Water Use: Turn off taps, take shorter showers, water plants efficiently, and run full loads in appliances.
• Reduce, Reuse, Recycle: Choose reusable items, repair and repurpose goods, separate waste diligently, and buy less.
• Sustainable Food Choices: Reduce food waste, eat more plant-based meals, buy local and seasonal produce, and choose sustainably sourced products.
• Eco-Friendly Transportation: Walk, cycle, use public transport, carpool, drive efficiently, and consider alternatives to flying for short distances.
• Energy Conservation: Unplug unused electronics, use energy-efficient appliances, insulate homes well, use natural light, and switch to LED bulbs.
• Choose Greener Products: Opt for eco-friendly cleaning products, avoid pesticides, and dispose of hazardous waste responsibly.
• Respect and Protect Nature: Avoid littering, support conservation efforts, choose sustainable tourism, and be mindful of wildlife and habitats.

EXERCISES

A. Fill in the blanks.

1. ______ per cent of the atmosphere is made of nitrogen.

Ans: 78%

2. Along with carbon dioxide and methane, ________ is a potent greenhouse gas.

Ans: water vapour

3. The rate at which the temperature drops in the ________  is 1°C per 165 metres.

Ans: troposphere 

4. The ________ is the layer of the atmosphere that help in radio transmission.

Ans: thermosphere

5. The upper part of the thermosphere is called the ________.

Ans: ionosphere

B. Match the following.

Answer:

C. Choose the correct answer.

1. This per cent of the atmosphere is composed of nitrogen.

1. 99
2. 78
3. 21
4. 76

Ans : 78

2. 21 per cent of the atmosphere is composed of

1. Helium
2. Oxygen
3. Nitrogen
4. Hydrogen

Ans : Oxygen

3. This gas protects us from the harmful ultraviolet radiation.

1. Oxygen
2. Ozone
3. Helium
4. Hydrogen

Ans : Ozone

4. The rate at which the temperature drops in the troposphere is called

1. lapse rate
2. loss rate
3. less rate
4. drop rate

Ans : Lapse rate

5. This layer of the atmosphere has the lowest temperature.

1. Mesosphere
2. Thermosphere
3. Tropopause
4. Stratosphere

D. State whether the following are true or false.

1. The earth’s atmosphere contains 99 per cent oxygen, which is essential for life.
Ans: False.
Correct : The earth’s atmosphere contains 21% per cent oxygen, which is essential for life.

2. The stratosphere is the lowest layer of the atmosphere.
Ans: False.
Correct : The troposphere is the lowest layer of the atmosphere.

3. The temperature drops at the rate of 1°C per 185 metres in the atmosphere.
Ans: False.
Correct : The temperature drops at the rate of 1°C per 165 metres in the atmosphere.

4. The stratosphere extends from the top of the troposphere up to 80 km above the surface of the earth.
Ans: False.
Correct : The stratosphere extends from the top of the troposphere up to 50 km above the surface of the earth.

5. Communication satellites orbit in thermosphere.
Ans: True.

E. Answer the following questions in brief.

Question 1.
How is the atmosphere kept in place around the earth?
Ans:

Here’s a simple explanation:

• Gravity’s Pull: Just as gravity pulls everything towards the Earth’s surface (like you and me, or a ball you throw up), it also pulls the gases that make up the atmosphere towards the Earth.  
• Mass Matters: The Earth has a significant amount of mass, and therefore a strong gravitational pull. This pull extends outwards into space, although its strength decreases with distance.
• Atmospheric Gases Have Mass: The gases that constitute the atmosphere, though seemingly light, do have mass. Gravity acts on this mass, constantly drawing the gas molecules downwards.
• Balance: While the gas molecules have some kinetic energy (they are constantly moving), This prevents them from escaping into outer space.

Question 2.

Name the important gases that are found in the atmosphere.

Ans:

The most important gases in the atmosphere are Nitrogen (78%), Oxygen (21%), Argon (0.9%), Carbon Dioxide (around 0.04%), and Water Vapor (variable, 0-4%). These gases are vital for life, weather, and regulating Earth’s temperature.

Question 3.

How is carbon dioxide a useful gas for life on earth?

Ans:

Carbon dioxide is super important for life because plants take it in to make their own food through photosynthesis, and in that process, they release the oxygen that we and most other animals need to breathe. It also helps keep Earth at a cozy temperature because it traps some heat, like a greenhouse. Plus, it’s involved in making the shells of many sea creatures. So, even though too much is a problem now, it’s a gas that life on Earth really depends on.

Question 4.

What is the troposphere?

Ans:

The troposphere is Earth’s lowest atmospheric layer, the one nearest to the ground where we live. It is in this zone that almost all weather phenomena occur, including rain, wind, and storms. This layer holds the greatest portion of the atmosphere’s gases, and typically, its temperature declines as altitude increases.

Question 5.

What is the difference between the troposphere and the tropopause?

Ans:

The troposphere is the bottommost layer of the atmosphere, the region closest to the Earth’s surface where we reside and where virtually all weather phenomena occur. A defining feature of this layer is that its temperature typically declines as altitude increases.

It’s characterized by the point where the temperature ceases to decrease with height, effectively acting as a boundary that separates the turbulent troposphere from the more stable stratosphere above.

F. Answer the following questions in one or two paragraphs.

Question 1.
Write briefly about the layers of the atmosphere.
Ans:

Earth’s atmosphere has five main layers: the troposphere (weather, gets colder), stratosphere (ozone, gets warmer), mesosphere (coldest, meteors burn), thermosphere (hot, radio/auroras), and exosphere (outermost, satellites). Each plays a vital role.

Question 2.

State any three characteristics of the stratosphere.

Ans:

Here are three key features of the stratosphere:

1. It is situated above the troposphere.
2. It includes the ozone layer, which blocks much of the sun’s damaging UV rays.
3. Its temperature typically rises with increasing altitude.

Question 3.

What is ozone? What is the ozone layer? How is the presence of ozone layer essential to preserve life on earth?

Ans:

It functions as a protective barrier, absorbing the majority of the Sun’s dangerous ultraviolet (UV) radiation, especially UV-B and UV-C rays. If the ozone layer didn’t exist, these high-energy UV rays would bombard the Earth’s surface, leading to significant harm such as DNA damage, increased rates of skin cancer, harm to ocean ecosystems and plant growth, and weakened immune systems in animals. Therefore, the ozone layer plays a vital role in making Earth a habitable place for a wide variety of organisms.

Question 4.

State any three characteristics of the mesosphere.

Ans:

Here are three distinct features of the mesosphere:

1. It resides above the stratosphere.
2. It is the atmosphere’s coldest region.
3. The majority of meteors disintegrate within this layer due to atmospheric drag.

Question 5.

Why is the thermosphere important ?

Ans:

The thermosphere holds significance for several key reasons:

• It offers a degree of protection from intense solar radiation, absorbing very high-energy forms like X-rays.
• It contains the ionosphere, a region of charged particles vital for long-distance radio communication by reflecting radio waves.
• It is the site of the breathtaking auroras (Northern and Southern Lights), resulting from interactions between solar particles and atmospheric gases.
• Its upper reaches provide orbital space for many satellites, which are crucial for communication, navigation, weather monitoring, and scientific study.

Question 6.

Explain the significance of the earth’s atmosphere.

Ans:

The Earth’s atmosphere is vital because it provides the air we breathe, regulates our planet’s temperature, shields us from harmful radiation and space debris, facilitates the water cycle, enables long-distance communication, and drives weather and climate. It’s essential for life as we know it.

G Picture study :
This is a picture of a supersonic aircraft.

Question 1.
In which layer of the atmosphere does this airplane normally fly?
Ans:
A supersonic aircraft fly in stratosphere.

Question 2.
This layer of the atmosphere is also known to protect living beings from the harmful rays of the sun. How?
Ans:

The layer of air that keeps living things safe from the sun’s harmful light is the stratosphere. Within the stratosphere is a special area called the ozone layer. Ozone molecules in this layer can soak up most of the sun’s dangerous ultraviolet (UV) rays, especially the really harmful ones called UV-B and UV-C. By grabbing these rays, the ozone layer works like a natural sunscreen for Earth. This stops too much of this harmful light from reaching the ground, which helps protect plants, animals, and people from getting hurt by it.

LET’S DO SOMETHING
In your notebooks, draw a diagram showing the layers of the atmosphere. Mark clearly the ozone layer, the height at which a jet plane can fly and also the height up to which birds can fly.
Ans: