c13 -

Question 1

which elements are in the air? and how much of them are present?

Answer 1

• nitrogen: 78
• oxygen: 21
• argon: 0.9
• water vapour: 0.1
  carbon dioxide: 0.04

Question 2

how did the atmosphere evolve?

Answer 2

1) earth is a ball of molten rock. no atmosphere is present
2) earth is still too hot for any surface water. it is covered in volcanoes.
3) earth starts to cool down. water vapour begins to condense and oceans are formed
4) life begins in oceans. simple plants called cyanobacteria use carbon dioxide in photosynthesis. ozone forms and oxygen levels start to rise.
5) land plants start to appear. oxygen levels rise rapidly
6) animals evolve due to the increase in oxygen
7) balance between carbon dioxide and oxygen is achieved
8) carbon dioxide levels rise due to pollution. global warming starts - weather patterns affected

Question 3

what was the first source of gas in the early atmosphere and which gas did it release?

Answer 3

volcanoes released mainly carbon dioxide

Question 4

what are some ways in which carbon dioxide levels can be reduced?

Answer 4

• oceans absorbing carbon dioxide
• plants photosynthesising
• some carbon dioxide became ‘locked’ in rocks

Question 5

how can carbon dioxide become locked in rocks?

Answer 5

• carbon dioxide is taken in by plants and converted into glucose
• the carbon in the glucose can then end up in plant material, which is eaten by animals and transferred to their tissues (skeletons and shells)
• these marine organisms then build up at the bottom of the ocean (layers and layers of sediment) → forms coal, oil and natural gas

Question 6

how did ammonia and methane come to be in the atmosphere?

Answer 6

• volcanoes also produced nitrogen gas in the early atmosphere; this also contained some amounts of methane and ammonia gases
• any methane and ammonia found reacted with the oxygen formed by the evolving plants and algae
• this removed methane and ammonia from the earth’s atmosphere but the levels of nitrogen could continue to rise

Question 7

what were the first organisms to produce oxygen on earth?

Answer 7

• cyanobacteria / algae

Question 8

how does oil form?

Answer 8

dead marine organisms forming layers and layers on the bottom of the ocean

Question 9

what are the main greenhouse gases?

Answer 9

• carbon dioxide
• methane
• water vapour

Question 10

what is the greenhouse effect?

Answer 10

• the sun emits short wavelength radiation
• this passes through the atmosphere but is absorbed by the earth
• earth re-emits it as longer wavelength thermal energy
• this can be absorbed by gases and radiated all around the atmosphere (trapped)

Question 11

how has human activity led to an increase in greenhouse gas emissions?

Answer 11

• burning fossil fuels in industry
• deforestation - stops some of the CO2 being absorbed for photosynthesis
• waste going to landfill releases CO2 and methane when burnt
• paddy fields (rice) and breeding cattle for food produces methane

Question 12

what are the effects of the global temperatures rising?