**Atmosphere Composition:** Nitrogen 78%, Oxygen 21%, Argon 0.93%, CO₂ 0.04%, others 0.03%; water vapour 0.1–0.4%.
**Five Atmospheric Layers (from Earth):**
• **Troposphere:** 0–12 km; temperature decreases; all weather occurs here
• **Stratosphere:** 12–50 km; contains ozone layer; ideal for aeroplanes
• **Mesosphere:** 50–80 km; temperature decreases; meteors burn here
• **Thermosphere:** 80–700 km; temperature increases; auroras and radio transmission occur
• **Exosphere:** 700+ km; very thin air; light gases escape
**Weather vs Climate:** Weather = daily/hourly changes; Climate = 30+ year average.
**Key Concepts:** Insolation decreases equator→poles. Ozone filters UV. Atmosphere traps heat. Air pressure equals throughout body.
Q1. Which gas makes up approximately 78% of Earth's atmosphere?
Answer: B — Nitrogen comprises 78% of the atmosphere and is essential for life as it supports plant growth and various biological processes.
Q2. At what average height does the troposphere extend?
Answer: B — The troposphere extends to an average height of 12 kilometres and is the most important layer where all weather phenomena occur.
Q3. Which atmospheric layer contains the ozone that protects Earth from ultraviolet radiation?
Answer: C — The stratosphere (12–50 km) contains the ozone layer, a critical feature that filters harmful ultraviolet radiation from the Sun.
Q4. Which of the following statements about temperature in atmospheric layers is NOT correct?
Answer: D — Temperature actually increases in the stratosphere due to ozone absorption of solar radiation, making option D incorrect while others are true.
Q5. Priya observes that weather changes from day to day in her city, but the overall climate remains similar year after year. What is the key difference she is noticing?
Answer: B — Weather refers to hour-to-hour and day-to-day changes, while climate is the sum of weather conditions over extended periods of 30+ years.
Q6. How does insolation affect temperature distribution on Earth?
Answer: C — Insolation (incoming solar energy) decreases from the equator to the poles, causing equatorial regions to be warmer than polar regions.
Q7. Which of the following is a correct match between atmospheric layer and its characteristic?
Answer: C — Most meteorites entering from space burn up in the mesosphere due to friction with atmospheric gases at that altitude.
Q8. Why does the atmosphere not crush our bodies despite exerting significant pressure on us?
Answer: C — Air pressure acts on us from all sides and our bodies exert equal counter-pressure in response, resulting in no net force felt by us.
Q9. In which atmospheric layer does the Aurora Borealis occur and why?
Answer: C — The Aurora Borealis occurs in the thermosphere when charged particles from the Sun interact with different atmospheric gases, causing them to glow.
Q10. Which statement best explains why the atmosphere is essential for life on Earth?
Answer: B — The atmosphere serves multiple critical functions: shielding from UV radiation, trapping heat for temperature regulation, and providing essential gases like oxygen.
What is the atmosphere?
A blanket of air surrounding Earth, held by gravity, composed of gases essential for life and shielding us from harmful solar radiation.
Name the two most abundant gases in the atmosphere.
Nitrogen (78%) and oxygen (21%) are the two primary gases that sustain all life on Earth.
What is the troposphere and why is it important?
The troposphere is the lowest layer (12 km high) where we breathe, weather forms, and nearly all precipitation occurs.
Which layer contains the ozone and what does it do?
The stratosphere contains the ozone layer, which filters the Sun's harmful ultraviolet radiation and protects life on Earth.
How does temperature change in the troposphere and mesosphere?
Temperature decreases with increasing altitude in both the troposphere and mesosphere, making them unique among atmospheric layers.
What happens to temperature in the thermosphere?
Temperature rises rapidly with increasing altitude in the thermosphere as gas molecules absorb X-rays and ultraviolet radiation.
Define weather and climate with one key difference.
Weather is hour-to-hour atmospheric conditions while climate is the average weather pattern over 30+ years for a region.
What is insolation and how does it affect temperature?
Insolation is incoming solar energy that decreases from the equator to the poles, causing temperature variation across latitudes.
Name three major elements that influence weather and climate.
Temperature, precipitation, humidity, wind, and atmospheric pressure are the five major elements affecting weather and climate.
What is the exosphere and what happens there?
The exosphere is the uppermost atmospheric layer with very thin air where light gases like helium and hydrogen escape into space.
Name the two most abundant gases in the atmosphere and state their approximate percentages. [2 marks]
Look at the composition pie chart; Nitrogen and Oxygen are the primary gases. State their exact percentages: 78% and 21%.
Explain how the ozone layer in the stratosphere protects life on Earth. Why is the stratosphere ideal for flying aeroplanes? [3 marks]
The ozone layer filters ultraviolet radiation, protecting organisms from harm. Aeroplanes fly here because it is free of clouds and weather disturbances. Connect both reasons to the stratosphere's position and composition.
Analyse the relationship between the five atmospheric layers and the phenomena that occur within them. How do the different temperature patterns in these layers influence Earth's weather and climate? [5 marks]
Describe each layer (troposphere, stratosphere, mesosphere, thermosphere, exosphere) with their altitude, temperature patterns, and specific phenomena (weather, auroras, meteors). Explain how temperature variations and layer functions (ozone protection, heat trapping, convection in troposphere) directly cause weather patterns and climate differences. Link insolation and altitude to temperature distribution.
Practice with interactive flashcards, mind maps, upload your own chapters and get AI study kits instantly
Try StudyOS Free →