C9 - Chemistry of the Atmosphere

• What gases make up the Earth's atmosphere today, and what are their approximate percentages?

  • The Earth's atmosphere today consists of approximately:
  • 78% nitrogen,
  • 21% oxygen,
  • 0.9% argon,
  • 0.04% carbon dioxide,
  • Trace amounts of other gases, including water vapor.
• What evidence suggests that the Earth's early atmosphere contained large amounts of carbon dioxide?

  • Evidence includes:
  • The presence of carbonate rocks (e.g., limestone) formed from carbon dioxide.
  • The lack of oxygen in early rocks and fossils.
• How did the amount of oxygen in the Earth's atmosphere increase over time?

  • Oxygen levels increased due to photosynthesis by algae and plants, which converted carbon dioxide and water into oxygen and glucose.
• What role did photosynthesis play in changing the composition of the Earth's atmosphere?

  • Photosynthesis removed carbon dioxide and released oxygen, gradually increasing oxygen levels and decreasing carbon dioxide levels.
• Explain how carbon dioxide was removed from the early atmosphere.

  • Carbon dioxide was removed by:
  • Dissolving in oceans and forming carbonate precipitates.
  • Being incorporated into sedimentary rocks like limestone.
  • Being used by plants and algae during photosynthesis.
• What is the significance of limestone and fossil fuels in understanding the history of the Earth's atmosphere?

  • Limestone and fossil fuels store carbon that was once in the atmosphere, providing evidence of past carbon dioxide levels.
• How did the formation of oceans contribute to changes in the Earth's atmosphere?

  • Oceans absorbed large amounts of carbon dioxide, reducing its concentration in the atmosphere and allowing oxygen levels to rise.
• Describe how the Earth's early atmosphere was formed.

  • The Earth's early atmosphere was formed by volcanic activity, which released gases such as carbon dioxide, water vapor, nitrogen, and small amounts of methane and ammonia.
• What are greenhouse gases, and name three examples.

  • Greenhouse gases trap heat in the Earth's atmosphere. Examples include carbon dioxide, methane, and water vapor.
• Explain how greenhouse gases contribute to the greenhouse effect.

  • Greenhouse gases absorb and re-radiate infrared radiation, trapping heat in the atmosphere and warming the Earth's surface.
• Describe the role of carbon dioxide and methane in maintaining global temperatures.

  • Carbon dioxide and methane absorb infrared radiation, preventing it from escaping into space and helping to maintain Earth's temperature.
• How do human activities increase the levels of carbon dioxide in the atmosphere?

  • Human activities such as burning fossil fuels, deforestation, and industrial processes release large amounts of carbon dioxide.
• What are the main sources of methane in the atmosphere?

  • Sources include agriculture (e.g., cattle farming), landfills, and the extraction of fossil fuels.
• Explain the potential consequences of climate change on the environment.

  • Rising sea levels due to melting ice caps.
  • More frequent and severe weather events.
  • Loss of biodiversity and habitat destruction.
• How can scientists use data from ice cores to study past climate change?

  • Ice cores trap air bubbles, which provide information about past atmospheric composition and temperature.
• What is the correlation between atmospheric carbon dioxide levels and global temperatures?

  • Higher carbon dioxide levels correlate with higher global temperatures due to the enhanced greenhouse effect.
• What is meant by the term "carbon footprint"?

  • A carbon footprint is the total amount of greenhouse gases emitted directly or indirectly by an individual, organization, or product.
• List three actions individuals can take to reduce their carbon footprint.

  • Using public transport or cycling instead of driving.
  • Reducing energy consumption at home (e.g., turning off lights).
  • Eating less meat and dairy.
• How can governments and industries reduce carbon emissions on a larger scale?

  • Invest in renewable energy sources.
  • Implement carbon capture and storage (CCS) technologies.
  • Enforce regulations to limit emissions.
• Explain the benefits and drawbacks of using renewable energy sources to reduce carbon footprints.

  • Benefits include reduced greenhouse gas emissions and sustainability.
  • Drawbacks include high initial costs and variability in energy supply.
• How does deforestation contribute to an increase in carbon dioxide levels?

  • Deforestation reduces the number of trees that can absorb carbon dioxide through photosynthesis, increasing atmospheric CO₂ levels.
• What is the role of reforestation in reducing carbon dioxide in the atmosphere?

  • Reforestation increases the number of trees, which absorb carbon dioxide during photosynthesis, reducing atmospheric CO₂ levels.
• Name two gases that are considered atmospheric pollutants and explain their sources.

  • Examples include:
  • Sulfur dioxide (from burning fossil fuels).
  • Nitrogen oxides (from vehicle emissions).
• What are the environmental impacts of sulfur dioxide emissions?

  Sulfur dioxide causes acid rain, which harms ecosystems, damages buildings, and affects human health.
• How do nitrogen oxides form in the atmosphere, and what problems do they cause?

  Nitrogen oxides form during combustion at high temperatures. They contribute to acid rain, smog, and respiratory problems.
• Explain how carbon monoxide is produced and why it is dangerous to humans.

  Carbon monoxide is produced by incomplete combustion of fuels. It is dangerous because it binds to haemoglobin, reducing oxygen transport in the blood.
• How can catalytic converters in vehicles reduce atmospheric pollution?

  Catalytic converters convert harmful gases (e.g., carbon monoxide, nitrogen oxides) into less harmful substances (e.g., carbon dioxide, nitrogen).
• Design an experiment to measure the amount of carbon dioxide in a sample of air.

  • Use a gas syringe to collect air and pass it through limewater.
  • The limewater will turn cloudy as it reacts with carbon dioxide, and the volume of CO₂ can be calculated.
• Describe a method to test the pH of rainwater and determine if it is acidic.

  • Collect rainwater and use a pH meter or universal indicator to measure its pH.
  • A pH below 7 indicates acidity.