Chemistry-of-the-Atmosphere-Student-file

Atmosphere Composition and Structure

Overview

• Earth is the only planet known to support life, making air vital.

• Atmosphere: The layer of gases surrounding Earth, held by gravity.

• Protects against harmful UV rays and maintains suitable temperatures.

• Essential for all life forms.

Objectives

• Explain the composition of the atmosphere.

• Describe characteristics of different atmospheric layers.

• Explain the importance of the atmosphere and the cyclic processes of gases.

Composition of the Atmosphere

• Components: Mixture of gases, water vapor, and dust particles.

• Main Gases:

  • Nitrogen: 78.1%

  • Oxygen: 20.9%

• Other Gases:

  • Argon: 0.9%

  • Carbon Dioxide: 0.03%

  • Hydrogen: 0.01%

  • Trace elements include neon, helium, ozone, etc.

Ozone Gas

• Found in the ozone layer, absorbs UV rays, critical for life.

Water Vapor

• Present as gaseous water, essential for precipitation.

• Varies from 0% to 4% depending on humidity and temperature.

• Important processes: Evaporation (from water bodies) and transpiration (from plants).

Dust Particles

• Usually in lower atmosphere; involved in cloud formation and precipitation.

• Includes sand and smoke particles.

Importance of the Atmosphere

• Oxygen: Breathing for living beings.

• Carbon Dioxide: Essential for photosynthesis in plants.

• Water Vapor: Influences precipitation and climate.

• Ozone: Protects from UV radiation.

Structure of the Atmosphere

• Total height approximately 1600 km, but 97% of mass is within 30 km.

Layers of the Atmosphere

1. Troposphere

   • Lowest layer, height varies (18 km at the equator, 8 km at poles).

   • Weather occurrences happen here.

   • Temperature decreases with height, called normal lapse rate.

   • Upper boundary: Tropopause.

2. Stratosphere

   • Extends up to 50 km.

   • Contains ozone, temperature increases with height.

   • Ideal for aircraft travel due to stable conditions.

3. Mesosphere

   • Spans up to 80 km.

   • Temperature decreases, can drop to -100°C.

   • Location of meteor activity.

4. Ionosphere

   • Ranges up to 400 km; contains charged particles.

   • Reflects radio waves, aids communication.

5. Exosphere

   • Last layer, beyond 400 km, very thin air.

Cyclic Processes of Atmospheric Gases

1. Carbon Cycle

   • Carbon exists as CO2; plants use it for photosynthesis.

   • CO2 returns to the atmosphere through respiration, decay, and combustion.

2. Oxygen Cycle

   • Atmospheric oxygen is essential for respiration and combustion.

   • Produced mainly by plants through photosynthesis.

3. Nitrogen Cycle

   • Nitrogen (78% of atmosphere) is essential for life, primarily sourced from soil nitrates.

   • Nitrogen fixation transforms atmospheric nitrogen into usable forms for organisms.