Topic 9 Flashcards

Current & Early Atmosphere

Current & Early Atmosphere: read all 6 questions and answers

1. What are the approximate proportions of gases in today's atmosphere?
   Nitrogen ~78%, Oxygen ~21%, Argon ~0.9%, CO₂ ~0.04%, plus small amounts of water vapour and other trace gases.
2. How long has the atmosphere been roughly stable?
   For about 200 MILLION years the proportions have been broadly stable.
3. What was the early atmosphere mainly composed of?
   Mainly CARBON DIOXIDE (CO₂), similar to Mars and Venus today. Also water vapour, with little or no oxygen. Small amounts of methane and ammonia.
4. Where did the early atmosphere come from?
   Intense VOLCANIC ACTIVITY released gases from the Earth's interior, including CO₂, water vapour, nitrogen, methane, and ammonia.
5. Why are scientists uncertain about the exact early atmosphere?
   There were NO DIRECT MEASUREMENTS. Evidence comes from rocks, fossils, and comparing with other planets. We can only estimate.
6. What happened to the water vapour in the early atmosphere?
   As the Earth COOLED, water vapour CONDENSED to form the oceans.

How Oxygen Increased

How Oxygen Increased: read all 5 questions and answers

1. How did oxygen first appear in the atmosphere?
   Around 2.7 billion years ago, CYANOBACTERIA (algae) evolved and began photosynthesising - absorbing CO₂ and releasing O₂.
2. Write the photosynthesis equation.
   6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Carbon dioxide + water → glucose + oxygen.
3. How was CO₂ removed from the early atmosphere? (3 ways)
   1. DISSOLVED in the oceans (formed carbonate rocks/shells). 2. Used in PHOTOSYNTHESIS (locked in biomass). 3. Formed FOSSIL FUELS (dead organisms buried and compressed over millions of years).
4. What are the three main types of fossil fuel?
   COAL (from ancient plants), OIL and NATURAL GAS (from ancient marine organisms). All formed over millions of years from buried biomass.
5. How did the rise in oxygen allow more complex life?
   Oxygen built up in the atmosphere over hundreds of millions of years, eventually allowing AEROBIC organisms to evolve. The ozone layer (O₃) also formed, protecting life from UV radiation.

Greenhouse Gases & the Greenhouse Effect

Greenhouse Gases & the Greenhouse Effect: read all 6 questions and answers

1. What is the greenhouse effect?
   Greenhouse gases in the atmosphere ABSORB infrared (heat) radiation emitted by the Earth's surface and RE-RADIATE it in all directions, including back towards the surface. This keeps Earth warm enough for life.
2. Name the three main greenhouse gases.
   1. Carbon dioxide (CO₂). 2. Methane (CH₄). 3. Water vapour (H₂O).
3. What human activities increase CO₂ levels?
   BURNING FOSSIL FUELS (transport, industry, power generation) and DEFORESTATION (fewer trees to absorb CO₂, and burning releases stored carbon).
4. What human activities increase methane levels?
   CATTLE FARMING (digestive processes), RICE PADDIES (waterlogged soil), LANDFILL (decomposing waste), and NATURAL GAS leaks.
5. What is the enhanced greenhouse effect?
   The ADDITIONAL warming caused by INCREASED concentrations of greenhouse gases from human activities. More greenhouse gases trap more heat, raising global temperatures.
6. Is the greenhouse effect itself a bad thing?
   NO - the natural greenhouse effect is essential for life. Without it, Earth would be too cold (~-18°C). The problem is the ENHANCED greenhouse effect from extra greenhouse gases.

Climate Change & Carbon Footprint

Climate Change & Carbon Footprint: read all 7 questions and answers

1. What is climate change?
   A long-term shift in global or regional climate patterns. Since the Industrial Revolution, human activities have increased greenhouse gas concentrations, causing global warming.
2. List five consequences of climate change.
   1. Polar ice caps melting → sea level rise → flooding. 2. More extreme weather (droughts, storms, floods). 3. Changes to ecosystems and habitats. 4. Impact on agriculture and food production. 5. Migration of species to new areas.
3. Why is there debate about climate change?
   The vast majority of scientists agree humans are the main cause. But: climate models are COMPLEX, long-term data can be interpreted differently, and media/politics/economics influence perception. PEER REVIEW is vital.
4. What is a carbon footprint?
   The TOTAL amount of CO₂ and other greenhouse gases emitted over the FULL LIFE CYCLE of a product, service, or event.
5. List six ways to reduce carbon footprint.
   1. Use renewable energy (solar, wind, tidal). 2. Improve energy efficiency. 3. Carbon capture and storage (CCS). 4. Reduce, reuse, recycle. 5. Plant trees. 6. Use public transport/cycling.
6. Why is it difficult to reduce carbon footprint to zero?
   Requires major LIFESTYLE CHANGES, is ECONOMICALLY CHALLENGING, some processes have NO ALTERNATIVE to fossil fuels, and international agreement is needed.
7. What is carbon capture and storage (CCS)?
   Technology that captures CO₂ produced at power stations/factories and stores it underground (e.g. In depleted oil/gas reservoirs) so it is not released to the atmosphere.

Atmospheric Pollutants

Atmospheric Pollutants: read all 7 questions and answers

1. What is carbon monoxide (CO) and why is it dangerous?
   Formed by INCOMPLETE COMBUSTION. It is TOXIC - binds to haemoglobin in blood, preventing oxygen transport. It is colourless and odourless, making it very difficult to detect.
2. How is sulfur dioxide (SO₂) produced and what harm does it cause?
   Formed when fuels containing SULFUR IMPURITIES are burned. Dissolves in water in clouds → forms ACID RAIN, which damages buildings (limestone/marble), kills aquatic life, and harms plants.
3. How are nitrogen oxides (NOₓ) formed?
   At HIGH TEMPERATURES inside engines, nitrogen (N₂) and oxygen (O₂) from the AIR react. NOT from the fuel itself. Causes acid rain, photochemical smog, and respiratory problems.
4. What are particulates and what problems do they cause?
   Tiny particles of unburned CARBON (soot) from incomplete combustion. Cause RESPIRATORY PROBLEMS, darken buildings, and contribute to GLOBAL DIMMING (reflecting sunlight).
5. What is global dimming?
   A reduction in sunlight reaching the Earth's surface caused by PARTICULATES in the atmosphere reflecting and absorbing sunlight.
6. How do catalytic converters help reduce pollution?
   They convert toxic gases into less harmful ones: CO → CO₂ (carbon monoxide to carbon dioxide) and NOₓ → N₂ (nitrogen oxides to nitrogen). Found in car exhausts.
7. How can sulfur dioxide emissions be reduced?
   FLUE GAS DESULFURISATION at power stations (reacting SO₂ with calcium oxide/hydroxide) and using LOW-SULFUR FUELS.