C9 : Chemistry of the Atmosphere

How old is the Earth?

4.6 billion years old

What are the proportions of gases are there in the atmosphere today?

• Approximately 78% nitrogen

• Approximately 21% oxygen

• Small amounts of other gases ~ carbon dioxide, water vapour and noble gases (less than 1%)

How long have the gases in the atmosphere stayed constant for?

200 million years

What was the early atmosphere mostly made up of?

Carbon dioxide

The Earth’s early atmosphere can be compared to which planets today?

Mars + Venus

In the first billion years what was the Earths surface mostly covered in?

Covered in volcanoes

What did intense volcanic activity produce in the early atmosphere? (5)

• Nitrogen

• Water vapour

• Methane

• Ammonia

• Carbon Dioxide

How were oceans formed?

As the earth cooled, the water vapour released by the volcanoes condensed to form oceans

Explain how the amount of oxygen in the atmosphere increased

Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis

How long ago did algae produce oxygen?

2.7 billion years ago

What did the build up of oxygen lead to?

Complex life such as animals to evolve

How was the percentage of carbon dioxide reduced in the atmosphere? (4)

• Carbon dioxide dissolving in water

• Photosynthesis of algae

• Formation of fossil fuels

• Sedimentary rocks

Explain how was the percentage of carbon dioxide reduced in the atmosphere when carbon dioxide dissolved in water

Carbon dioxide was dissolved in water and carbonates were precipitated producing carbonate sediments on the sea bed.

Explain how the percentage of carbon dioxide reduced in the atmosphere as a result of photosynthesis

Plants and algae needed carbon dioxide to photosynthesise

Explain how dead plants reduced the carbon dioxide in the atmosphere (3)

• Plants took in carbon dioxide because of photosynthesis

• When they died they were buried by layers of sediment

• Over millions of years they became compressed and formed the sedimentary rocks/fossil fuel - trapping carbon dioxide and reducing it from the atmosphere

Define plankton

Organisms that can be moved by ocean currents

Explain how crude oil and natural gas are formed

Formed from deposits of plankton over millions of years by being exposed to high temperatures + pressures

Explain how coal is formed

Formed from thick deposits of dead plant material over millions of years by being exposed to high temperatures + pressures

What is limestone?

A sedimentary rock

Explain how limestone is formed

Mainly formed from calcium carbonate deposits from the shells and skeletons of marine organisms

What is the job of greenhouse gases?

Create an insulating layer in the Earths atmosphere which maintains temperatures

Why are greenhouse gases important?

Allows the Earth to be warm enough to support life

What are the 3 main greenhouse gases?

• Water vapour

• Carbon dioxide

• Methane

Explain the greenhouse effect in terms of the interaction of short and long wavelength radiation (7)

1. Energy from the sun travels to the Earth as short wavelength radiation (e.g. ultra violet and visible light)

2. The energy of the radiation is absorbed when it reaches the surface of the Earth

3. The surface of the Earth then re-emits the energy as long wavelength radiation (e.g. infra-red)

4. Some of the long wavelength radiation reflects back into space

5. But some of the long wavelength radiation interacts with the greenhouse gas molecules in the atmosphere and the energy in the long wavelength radiation is absorbed

6. The greenhouse gases then re-emit the thermal radiation in all direction including towards the earth

7. Because the energy is trapped in the atmosphere this causes the temperature to increase

What are the 2 ways humans increase the amount of carbon dioxide in the atmosphere?

• Deforestation → leads to less trees photosynthesising which leads to less carbon dioxide being absorbed

• Burning fossil fuels → releases carbon dioxide

What are the 2 ways humans increase the amount of methane in the atmosphere?

• Agriculture → farm animals produce more methane through their digestive processes (farting)

• Decomposition of landfills → releases methane

What is the importance of peer review?

Makes information reliable

Why is there speculation on the causes of global warming?

Simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased

What are the consequences of climate change? (4)

• Melting of polar ice caps, causing a rise in sea levels, increased flooding in costal areas and costal erosion

• Increase in extreme weather (droughts, hurricanes floods)

• Changes in rainfall patterns and increase in temperatures will lead to species not being adapted to their new environments and crops not having the correct conditions to grow

• Tropical diseases such as malaria would be more common in areas that aren’t tropical such as the UK

What is a carbon footprint?

The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.

How could carbon footprints be reduced? (8)

• Use renewable energy sources instead of fossil fuels

• Be efficient processes to reduce waste which reduces emissions of methane

• Governments can tax people on the amount of greenhouses gases they emit

• Governments can put a cap (limit) on emissions of all greenhouse gases that companies make

• Invest in technology that captures carbon dioxide

• Walk instead of driving

• Become a vegetarian

• Improve home insulation

Why is it difficult for people to reduce their carbon footprints? (4)

• Governments are worried that if they prioritise the environment it will impact economic growth of communities

• Hard to makes international agreements to reduce emissions because countries don’t want to sacrifice their economic development if others won’t do the same

• Individuals don’t want to change their lifestyles

• Too expensive

What are released when fossil fuels are burned? (6)

• Carbon dioxide

• Carbon monoxide

• Water vapour

• Sulfur dioxide

• Oxides of nitrogen

• Particulates

When is carbon dioxide released + what are its effects?

• Released → complete combustion of fossil fuels with an excess of oxygen

• Effects → a greenhouse gas which causes global warming

When is carbon monoxide released + what are its effects?

• Released → incomplete combustion of carbon fuels with a lack of oxygen

• Effects → Colourless, odourless and very hard to detect

  → dangerous as it binds with the haemoglobin and reduces the amount of oxygen in the blood as a result

  → lack of oxygen causes fainting, a coma or death

When is water vapour released + what are its effects?

• Released → complete/incomplete combustion of fossil fuels

• Effects → a greenhouse gas which causes global warming

When is sulfur dioxide released + what are its effects?

• Released → when coal is burned, sulfur atoms are oxidised

• Effects → causes acid rain which kills plants and damages buildings and statues, also makes metal corrode

  → also causes respiratory problems if breathed in

When are oxides of nitrogen released + what are their effects?

• Released → a reaction between nitrogen and oxygen in the air caused by the heat of burning at high temperatures (happens mainly in the internal combustion engines of cars)

• Effects → causes acid rain which kills plants and damages buildings and statues, also makes metal corrode

  → also causes respiratory problems if breathed in

When are particulates released + what are their effects?

• Released → unburned particles of hydrocarbons

• Effects → cause respiratory problems if inhaled as they get stuck in lungs and cause problems

  → also reflect sunlight back into space leading to less light reaching the Earth and causing global dimming