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gcse chemistry > c13 - the earth's atmosphere > Flashcards

c13 - the earth's atmosphere Flashcards

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1
Q

how much nitrogen is in our atmosphere?

A

78%

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2
Q

define greenhouse layer

A

layer of gases (e.g carbon dioxide, methane, water vapour) which absorb infrared radiation emitted from Earth

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3
Q

how much oxygen is there in our atmosphere?

A

21%

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4
Q

why don’t scientists know about gases in the early atmosphere?

A
  • 4.6 billion years ago
  • lack of evidence
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5
Q

what was believed about the early atmosphere?

A
  • mainly carbon dioxide, water vapour, methane, ammonia and nitrogen
  • Earth’s surface covered in volcanoes
  • little to no oxygen around this time which resembles the atmosphere’s today on mars and venus
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6
Q

what happened in the first billion years?

A

intense volcanic activity released the gases that formed the early atmosphere

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7
Q

what happened once the earth cooled down?

A

water vapour in the atmosphere condensed to oceans

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8
Q

how was amount of carbon dioxide in the atmosphere reduced?

A

1) dissolved into oceans
2) insoluble carbonate compounds produced
3) then these precipitated on the seabed as sediments

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9
Q

when did plants and algae evolve?

A

approximately 2.7 billion years ago

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10
Q

how did algae photosynthesise?

A

used energy transferred as light waves from the sun

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11
Q

give the equation for photosynthesis

A

carbon dioxide + water – (releasing light) –> glucose + oxygen

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12
Q

what was the effect of plants and algae evolving?

A
  • decreased amount of carbon dioxide
  • increased amount of oxygen
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13
Q

how were the first animals able to evolve?

A

levels of oxygen rose steadily

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14
Q

what happened to animal remains over millions of years?

A
  • became covered with layers of sediment at bottom of oceans
  • deposits formed sedimentary carbonate rocks under pressure of sediment
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15
Q

give and example of a sedimentary carbonate rock

A

limestone, consisting of calcium carbonate, formed from shells and skeletons of marine organisms

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16
Q

how was coal formed?

A
  • sedimentary rock, formed from thick deposits of plant material
  • plant material was buried and in abscence of oxygen, compressed over millions of years
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17
Q

how were crude oil and natural gas formed?

A
  • formed in remains of plankton deposited in mud on seabed
  • remains covered by sediments which became layers of rock when compressed over millions of years
  • crude oil and natural gas trapped in layers of rock
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18
Q

what other gases did volcanoes produce?

A
  • nitrogen gas, which gradually built up in the early atmosphere
  • small proportions of methane and ammonia gases
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19
Q

how were methane and ammonia removed from the atmosphere?

A
  • by reacting with oxygen produced by photosynthesis
  • reactions produced carbon dioxide and nitrogen
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20
Q

why did levels of nitrogen gas in the atmosphere build up?

A

nitrogen is a very unreactive gas

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21
Q

how much change has there been over the past 200 million years in the atmosphere?

A

not much change

22
Q

what is the role of greenhouse gases in the atmosphere?

A

maintain temperatures on Earth that are high enough to support life

23
Q

what are the main greenhouse gases in the earth’s atmosphere?

A

carbon dioxide, methane, water vapour

24
Q

how does the greenhouse layer insulate the Earth?

A
  • allows short wave infrared radiation emitted by the sun to pass through it
  • absorbs long wave infra red radiation which is emitted by the Earth
25
Q

how does the surface of the earth cool down?

A

by emitting longer wavelength infrared radiation

26
Q

what happens to some of the energy radiated from the surface of the earth?

A

gets trapped in the atmosphere and temperature rises

27
Q

the higher the proportion of greenhouse gases…

A

the more energy is absorbed

28
Q

why has there been a great increase in amount of carbon dioxide in atmosphere over past 100 years?

A

due to an increased use of fossil fuels, which when burnt release carbon dioxide into the atmosphere

29
Q

describe the effect of deforestation

A

trees are cut down so less carbon dioxide is removed from the air because photosynthesis is reduced

30
Q

what happens to carbon dioxide as the temperature rises?

A

gets less soluble in water, oceans become less effective as carbon dioxide sinks

31
Q

give two main reasons for an increase of methane in the air.

A
  • more animal farming leading to more emissions and decomposing waste
  • increased waste, so more decomposition of rubbish in landfill sites
32
Q

what do mosts scientists believe and how do they know this?

A
  • they agree that a trend in global warming has started
  • views based on evidence presented in scientific journals
  • evidence is peer reviewed by other scientists
33
Q

why can’t scientists predict with certainty the effects of increasing levels of greenhouse gases?

A
  • could lead to biased opinions and evidence could be taken out of context
34
Q

give a major cause of climate change

A

global warming

35
Q

give 5 consequences of rising levels of greenhouse gases.

A

1) rising sea levels
2) more frequent and severe storms
3) changes in temperature and amount of rainfall
4) impact on food producing capacity of different regions
5) changes to distribution of wildlife species and some becoming extinct

36
Q

define carbon footprint of a product

A

total amount of carbon dioxide and other greenhouse gases emitted over its full life cycle

37
Q

give 7 actions to reduce carbon footprint

A

1) alternative energy supplies
2) biofuels increase usage
3) carbon taxes
4) diets, plant based
5) energy usage conserved
6) carbon capture and storage - fossil fuels
7) planting trees

38
Q

define biofuels

A

made from plant material and absorb carbon dioxide during photosynthesis, this is then returned to the atmosphere where they are burnt
- carbon neutral

39
Q

define carbon capture and storage

A

carbon dioxide produced in fossil fuel power stations is pumped deep underground and absorbed by porous rocks.

40
Q

give 5 problems which reducing carbon footprint include

A

1) scientific disagreement over cause of climate change
2) not focused targets on reducing greenhouse gsses
3) cost of manufacturing and transporting
4) restricting greenhouse gases hinder developing industries
5) lack of educations and lifestyle changes

41
Q

what happens when pure hydrocarbons burn completely and give an example

A

they are oxidised to carbon dioxide and water
when butane burns:
butane + oxygen –> carbon dioxide + water

42
Q

why would incomplete combustion occur?

A
  • when fuels dont burn completely
  • when fuels may contain other substances
43
Q

what does incomplete combustion produce?

A

carbon monoxide, some unburnt hydrocarbons and particulates (contain soot/carbon)

44
Q

define carbon monoxide and what it does

A
  • toxic gas
  • colourless, odourless so you don’t know if you are breathing it in
  • combines with haemoglobin in the blood and is carried around in your blood instead of oxygen
45
Q

what can particulates cause?

A
  • global dimming since they prevent sunlight reaching earth’s surface
  • lung damage in humans
46
Q

what do most fossil fuels contain?

A

sulfur compounds

47
Q

what happens when fossil fuels are burnt?

A

sulfur compound in fossil fuels produce sulfure dioxide

48
Q

what happens to the oxygen and nitrogen in the air when fuels are burnt?

A

high temp causes nitrogen oxides to form

49
Q

how is acid rain formed?

A

sulfure dioxide and nitrogen oxides

50
Q

what does acid rain cause?

A
  • breathing problems in humans
  • damages trees
  • kills animals and plants in lakes
  • attacks limestone buildings and metal structures

gcse chemistry (10 decks)

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