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chemistry > C9 (the atmosphere) > Flashcards

C9 (the atmosphere) Flashcards

1
Q

describe the atmosphere of the Earth today:

A
  • around 78% of the atmosphere is nitrogen
  • around 21% is oxygen
  • small proportions of other gases, such as carbon dioxide, water vapour, and noble gases (e.g. argon)

these gases have stayed pretty constant for around 200 million years.

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2
Q

why can scientists not be certain about the early atmosphere?

A

the Earth is around 4600 million years old.

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3
Q

what do scientists think about the first billion years of Earth?

A
  • intense volcanic activity. these released the gases that formed the atmosphere (i.e. water vapour)
  • as the Earth cooled (couldn’t form oceans initially, as the temperatures were over 100 degrees celsius), the water vapour condensed to form the oceans
  • volcanoes also released huge amounts of CO2, which is what the early Earth’s atmosphere consisted mainly of, with almost no oxygen (very much like the atmospheres of Mars and Venus today)
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4
Q

what gases did early volcanoes release, other than carbon dioxide and water vapour?

A
  • nitrogen, which gradually built up in the atmosphere
  • released small amounts of methane and ammonia
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5
Q

describe the overall early atmosphere of the Earth:

A
  • mainly carbon dioxide
  • small but increasing amounts of nitrogen
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6
Q

why have carbon dioxide levels decreased in the Earth’s atmosphere over time?

A
  • the water vapour from volcanoes condensed to form oceans
  • some of the carbon dioxide dissolved in the oceans to form a weak acid (carbonic acid)
  • this reacted with minerals in the sea to form precipitates, which over time formed sediments of carbonate rock on the sea bed
  • plants and plankton photosynthesised, taking in CO2. animals then eat the plants, taking in the carbon. these die, get covered at the bottom of the ocean, and undergo huge pressures and heat, forming fossil fuels
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7
Q

what was the carbon dioxide in the sea used for?

A
  • carbon particulates and acid used to make the corals and shells of organisms such as mussels
  • when these died, they formed limestone (sedimentary rock), which helps to absorb CO2 from the atmosphere
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8
Q

where has oxygen come from since the Earth’s early atmosphere?

A
  • around 2.7 billion years ago, photosynthetic algae first evolved in the oceans
  • photosynthesis produced oxygen (and also absorbed more carbon dioxide) which entered the atmosphere
  • over the following billion years, plants evolved, increasing the amount of oxygen in the atmosphere
  • at some point the level of oxygen reached the point where animals could evolve
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9
Q

what was the first organism to produce oxygen?

A

cyanobacteria

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10
Q

describe fossil fuels:

A
  • formed over millions of years
  • non-renewable
  • contain trapped carbon (part of the carbon dioxide taken in by photosynthesis)
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11
Q

how is coal formed?

FOSSIL FUEL

A
  • from the remains of ferns and trees
  • over time, the plant remains are covered with sediment and compressed
  • high temperature and pressure creates coal
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12
Q

when may coal not be formed?

A

if the ferns/trees die in marshy wetlands. they don’t decompose, due to a lack of oxygen/acidic conditions, both preventing bacteria from carrying out decomposition.

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13
Q

how is crude oil formed?

FOSSIL FUEL

A

from plankton (tiny plants/animals found under the sea). when they die, they settle on the sea bed (apart from in anoxic conditions, when they’re unable to decompose). over time, they’re compressed by sediment, and heat and pressure convert them to crude oil.

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14
Q

what is natural gas?

FOSSIL FUEL

A
  • mainly the hydrocarbon methane
  • often found near deposits of oil, as it’s formed from plankton in a similar way to crude oil
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15
Q

describe the small proportions of the greenhouse gases in the modern day atmosphere:

A

water vapour: amount varies, changes depending on temperature

carbon dioxide: around 0.04%

methane: tiny amounts

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16
Q

describe the greenhouse effect:

A
  • energy from the sun travels to Earth as short wavelength radiation (e.g. ultraviolet and visible light)
  • some of the short wavelength radiation simply reflects back into space, but most of it passes easily through the atmosphere, as short wavelength radiation doesn’t interact strongly with the gas molecules in the atmosphere
  • the energy of the radiation is absorbed when it reaches the surface of the Earth
  • the surface of the Earth now radiates energy as long wavelength radiation such as infrared
  • some of these interact with the greenhouse gas molecules in the atmosphere (the energy is absorbed). this causes the temperature of the atmosphere to increase
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17
Q

describe the importance of the greenhouse effect:

A

keeps the temperature on Earth warm enough to support life.

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18
Q

why are the levels of carbon dioxide currently increasing?

A
  • increasing as we burn fossil fuels (e.g. burning coal for electricity, petrol/diesel for cars, gas to heat our homes)
  • rainforests are being destroyed through deforestation (usually burned) to provide land for grazing cattle, so they can’t absorb carbon dioxide
  • burning the forests also produces large amounts of carbon dioxide
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19
Q

why are the levels of methane currently increasing?

A
  • released in agriculture (e.g. growing rice in flooded paddy fields, which generates methane emitting bacteria)
  • released when cows pass wind
20
Q

what does it mean if the levels of methane and carbon dioxide in the atmosphere increase?

A

the temperature of the atmosphere is rising as more of the sun’s energy is being trapped by these greenhouse gases.

21
Q

how is climate change measured?

A

by the changes in pattern of:
- temperature
- sunshine
- rainfall
- windspeed

22
Q

what are the effects of climate change?

A
  • rising temperatures increases the melting of polar ice sheets and glaciers, increasing sea levels
  • this could lead to more flooding of lowland areas and coastal erosion
  • climate change could lead to more severe weather
  • increasing temperatures could change the distribution of animals such as insects. may even change the distribution of insect-borne diseases (e.g. malaria)
  • changes in amount, timing and distribution of rainfall
23
Q

what is peer review?

A

evidence for theories is shared between many different scientists. these scientists can then criticise the evidence and decide whether it’s valid. it allows scientists to detect false claims (e.g. based on poor evidence/bias)

24
Q

why is climate change so difficult to model?

A
  • sometimes see stories in the media that are simplified or simply biased
  • see speculation based on only parts of the evidence. scientists must work harder to communicate the ideas around climate change to the general public
25
Q

what uncertainty is there surrounding climate change?

A

cannot predict with certainty how much the temperature of the atmosphere will increase (can lead to speculation in the media)

26
Q

what is a carbon footprint?

A

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

27
Q

how can we reduce our carbon dioxide emissions?

A
  • a lot of energy is used to heat homes, which comes from burning fossil fuels. we can instead insulate our homes/turn down the heating
  • a lot of carbon dioxide is produced by driving cars, and we can travel by public transport instead, which release less CO2 per passenger
  • we generate electricity by burning fossil fuels. we can switch to renewable sources of energy
28
Q

how can we reduce our electricity usage at home?

A
  • switch to energy saving lightbulbs
  • turn appliances off at the plug, rather than leaving them on standby
29
Q

describe the problems with the solutions to reducing carbon emissions:

A
  • expensive, people are reluctant to pay
  • inconvenient (public transport)
30
Q

how can we reduce methane emissions?

A
  • people can eat less beef and dairy products. however, people enjoy eating these and are unlikely to change their diets
  • landfills also emit methane. we can trap this released methane and burn it to produce electricity. however, this costs money
31
Q

what is a fuel?

A

fuels release energy when combusted (burned). examples include coal and hydrocarbons

32
Q

what are hydrocarbons most commonly used for?

A

to power vehicles such as cars, from petrol and diesel

33
Q

what happens when we burn hydrocarbons and coal?

A
  • both made up of only carbon and hydrogen atoms
  • when burned (complete combustion), the carbon and hydrogen atoms react with oxygen in the air (they’re oxidised)
  • this forms carbon dioxide (greenhouse gas), which contributes to climate change
  • other gases that can be released when a fuel is burnt include: water vapour, carbon monoxide, sulfur dioxide, oxides of nitrogen. solid particles and unburned hydrocarbons may also be released, forming particulates in the atmosphere
34
Q

what is carbon monoxide?

A
  • toxic gas with no colour/smell
  • can be detected using a carbon monoxide detector in your home
35
Q

what are the harmful effects of carbon monoxide, and how can we oppose it?

A

red blood cells pick it up, carrying it around the blood instead of oxygen. the victim becomes starved of oxygen, gets drowsy, loses consciousness, and can die
- ensure a sufficient supply of oxygen to engines, so carbon dioxide is still produced

36
Q

describe the formation of sulfur dioxide:

A
  • some fuels (e.g. coal) contain sulfur
  • when coal is burned, the sulfur is oxidised, producing sulfur dioxide
37
Q

how can we oppose the formation of sulfur dioxide?

A

sulfur impurities can be removed from a fuel before the fuel is burnt

38
Q

describe the formation of oxides of nitrogen

A
  • produced inside engines (e.g. in cars)
  • high temperatures cause nitorgen and oxygen from the air to react
  • produces a range of different molecules, collectively named as ‘oxides of nitrogen’
39
Q

what are the effects of sulfur dioxide and oxides of nitrogen?

A
  • cause breathing problems in humans (can trigger people’s asthma)
  • also dissolve in rainwater to form acid rains (damages trees, corrodes buildings made of limestone, kills animal and plant life in lakes)
40
Q

describe the formation of particulates, and their risks:

A
  • can damage human health (increase the risk of heart/lung disease)
  • also reduce the amount of energy from the sun that reaches the Earth’s surface (reflects sunlight back into space), called global dimming. it’s possible that this is affecting rainfall patterns
41
Q

how are particulates formed, and how can they be prevented?

A
  • diesel engines burn hydrocarbons with bigger molecules than those in petrol engines
  • when these large molecules react with O2, they don’t always burn completely
  • tiny solid particles containing carbon and unburned hydrocarbons are produced (particulates). they get carried into the air
  • switch to petrol engines/electric cars
42
Q

describe the full development of the atmosphere:

A
  1. Earth is a molten block of rock and minerals
  2. The Earth’s surface is covered in volcanoes, releasing carbon dioxide, water vapour, and nitrogen
  3. Earth’s early atmosphere consists of carbon dioxide, with some water vapour, nitrogen, and traces of methane and ammonia
  4. the water vapour condensed as the Earth cooled and rain fell, forming oceans
  5. comets also brought water
  6. bacteria first appeared
  7. algae and other life forms evolved. they could make their own food using the sun’s energy, with oxygen being their waste
  8. oxygen levels rise steadily as algae and bacteria fill the seas
  9. animals evolved using oxygen to respire
  10. our atmosphere today
43
Q

what is the ozone layer made up of?

A

oxygen

44
Q

describe the carbon cycle:

A
  • decomposition (soil bacteria and fungi respire, adding CO2 into the air). plant deposits can be compressed to form fossil fuels, which are then combusted, releasing fossil fuels
  • photosynthesis draws CO2 into plants. animals eat the CO2, passing it along. they then respire, releasing CO2 into the air
45
Q

what was required for animals to exist?

A
  • a temperature decrease
  • a CO2 decrease
  • the appearance of O2
  • the ozone layer
  • the formation of oceans
46
Q

what are two main points about the Earth’s atmosphere and its ozone layer?

A
  • the atmosphere is held to Earth by the force of gravity - its mass is attracted to the Earth’s surface
  • most of the Sun’s harmful ultraviolet rays are blocked by the ozone layer

chemistry (12 decks)

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