C9 (the atmosphere) Flashcards
describe the atmosphere of the Earth today:
- 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.
why can scientists not be certain about the early atmosphere?
the Earth is around 4.6 billion years old, so it’s only a theory
what do scientists think about the first billion years of Earth?
- intense volcanic activity. these released the gases that formed the atmosphere (lots of carbon dioxide, 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
- Earth’s early atmosphere was mainly carbon dioxide, with very little oxygen (very much like the atmospheres of Mars and Venus today)
what gases did early volcanoes release, other than carbon dioxide and water vapour?
- nitrogen, which gradually built up in the atmosphere
- released small amounts of methane and ammonia
describe the overall early atmosphere of the Earth:
- mainly carbon dioxide
- small but increasing amounts of nitrogen
why have carbon dioxide levels decreased in the Earth’s atmosphere over time?
- 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 carbon 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 sedimentary rock, oil, and gas, trapping the carbon
how do we know what substance will be formed, depending on the type of organism being buried and the conditions involved?
- crude oil and natural gas: mainly from dead plankton
- coal: sedimentary rock from thick deposits of dead plant material
- limestone: sedimentary rock from the calcium carbonate from the shells and skeletons of marine organisms
where has oxygen come from since the Earth’s early atmosphere?
- 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
what was the first organism to produce oxygen?
cyanobacteria
describe fossil fuels:
- formed over millions of years
- non-renewable
- contain trapped carbon (part of the carbon dioxide taken in by photosynthesis)
how is coal formed?
FOSSIL FUEL
- from the remains of ferns and trees
- over time, the plant remains are covered with sediment and compressed
- high temperature and pressure creates coal
when may coal not be formed?
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.
how is crude oil formed?
FOSSIL FUEL
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.
what is natural gas?
FOSSIL FUEL
- mainly the hydrocarbon methane
- often found near deposits of oil, as it’s formed from plankton in a similar way to crude oil
describe the small proportions of the greenhouse gases in the modern day atmosphere:
water vapour: amount varies, changes depending on temperature
carbon dioxide: around 0.04%
methane: tiny amounts
what is the greenhouse effect?
the warming of the Earth caused by the greenhouse gases
describe the greenhouse effect:
- energy from the sun travels to Earth as short wavelength radiation (e.g. ultraviolet and visible light)
- some of the short wavelength radiation is absorbed and heats up the ground, but most of it is re-emitted/reflected back into the atmosphere, and into space, as longer wavelength radiation
- although some of this energy actually does reach space, most of it is absorbed by particles of gas in the atmosphere
- after a short delay, these re-emit the energy in random directions. some will be re-emitted towards space, and some towards the Earth
- most of the energy will collide with other gas particles before it leaves the atmosphere
- this process happens over and over again, meaning the heat energy stays close to Earth
describe the importance of the greenhouse effect:
keeps the temperature on Earth warm enough to support life.
why are the levels of carbon dioxide currently increasing?
- increasing as we burn fossil fuels (e.g. burning coal for electricity, petrol/diesel for cars, gas to heat our homes), which releases the locked up carbon as carbon dioxide
- rainforests are being destroyed through deforestation (usually burned) to provide land for grazing cattle, so they can’t absorb carbon dioxide through photosynthesis
- burning the forests also produces large amounts of carbon dioxide
why are the levels of methane currently increasing?
- released in agriculture (e.g. growing rice in flooded paddy fields, which generates methane emitting bacteria)
- released during farm animal (e.g. cows) digestion, which is then released into the atmosphere
- our release of waste releases methane as the waste is decomposed by microorganisms
what does it mean if the levels of methane and carbon dioxide in the atmosphere increase?
the temperature of the atmosphere is rising as more of the sun’s energy is being trapped by these greenhouse gases.
how is climate change measured?
by the changes in pattern of:
- temperature
- sunshine
- rainfall
- windspeed
how do we know that global warming is happening?
we have records going back hundreds of years, and we can see the steady increase
what are the some examples of climate change?
- climate change = the effect of global warming on the planet
- rising temperatures increases the melting of polar ice sheets and glaciers, increasing sea levels (water also expands at higher temperatures, volume increases)
- this could lead to more flooding of lowland areas, seasonal flooding, submersion of islands/coastal towns and coastal erosion
- climate change could lead to more severe weather (hurricanes)
- 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 (droughts)
what is peer review?
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)
why is climate change so difficult to model?
- 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
what uncertainty is there surrounding climate change?
cannot predict with certainty how much the temperature of the atmosphere will increase (can lead to speculation in the media)
what is a carbon footprint?
total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service, or event.
what is the benefit of a carbon footprint?
- can work out how environmentally damaging something is, so we’re better able to decide whether or not it’s worth the cost
- we can also identify the most polluting activities in order to try and reduce their emissions
what would we need to take into account to work out something’s carbon footprint?
e.g. phone
- how all the raw materials were sourced
- the manufacturing process
- the total amount of power it uses over its lifetime
- how it’s disposed of
- the emissions produced from transporting the parts
- it’s almost impossible to accurately calculate something’s total carbon emissions
- however, a rough calculation can still give a good idea of the worst emitters, and we can then make sensible plans to try and reduce these emissions
how can we reduce our carbon dioxide emissions?
- 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 (wind, solar, nuclear)
- use more efficient manufacturing processes: less energy, less waste
- recycle it
how can we reduce our electricity usage at home?
- switch to energy saving lightbulbs
- turn appliances off at the plug, rather than leaving them on standby
describe the problems with the solutions to reducing carbon emissions:
- expensive, people are reluctant to pay (e.g. renewable energy is more expensive than fossil fuels. our entire economy is currently based on fossil fuels, making it hard to change)
- prioritising the environment means the whole economy may suffer. this makes international agreements difficult
- inconvenient (public transport)
how can government reduce the carbon footprint?
- introduce new laws
- tax companies based on how many greenhouse gases they emit
what is carbon capture technology?
captures the carbon dioxide formed when we burn fossil fuels before it can escape into the atmosphere
- it’s stored deep underground in cracks in the rocks (e.g. old oil wells), where it can’t escape into the environment
how can we reduce methane emissions?
- 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
what is a fuel?
fuels release energy when combusted (burned). examples include coal and hydrocarbons
what are hydrocarbons most commonly used for?
to power vehicles such as cars, from petrol and diesel
what happens when we burn hydrocarbons and coal?
- 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 and water
what is released during incomplete combustion?
- when there’s not enough oxygen available for complete combustion
- can form carbon monoxide, and particulates (solid particles of carbon which we call soot)
what is carbon monoxide?
- toxic gas with no colour/smell
- can be detected using a carbon monoxide detector in your home
what are the harmful effects of carbon monoxide, and how can we oppose it?
diffuses into the blood, binds to haemoglobin in the same place oxygen binds. the haemoglobin can now carry less oxygen, so less is transported around the body
- 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
describe the formation of sulfur dioxide:
- some fuels (e.g. coal) contain sulfur
- when coal is burned, the sulfur is oxidised, producing sulfur dioxide
how can we oppose the formation of sulfur dioxide?
sulfur impurities can be removed from a fuel before the fuel is burnt
describe the formation of oxides of nitrogen
- produced inside internal combustion engines (e.g. in cars)
- really high temperatures cause nitrogen and oxygen (both from the air) to react
- produces a range of different molecules, collectively named as ‘oxides of nitrogen’
what are the effects of sulfur dioxide and oxides of nitrogen?
- cause breathing problems in humans (can trigger people’s asthma)
- mix with clouds, they dissolve to form dilute sulfuric/nitric acid. this falls as acid rain. this can damage certain buildings/statues, corrode metals, damage plants
how can acid rain damage plants?
either lands directly on the plant or makes the surrounding soil more acidic, making it harder for the plant to grow
describe the formation of particulates, and their risks:
- can damage human health (if inhaled, can get stuck in the lungs and damage them, leading to respiratory problems)
- also reduce the amount of energy from the sun that reaches the Earth’s surface, as it forms dark cloud/smog (reflects sunlight back into space), called global dimming. it’s possible that this is affecting rainfall patterns
how are particulates formed, and how can they be prevented?
- 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
describe the full development of the atmosphere:
- Earth is a molten block of rock and minerals
- The Earth’s surface is covered in volcanoes, releasing carbon dioxide, water vapour, and nitrogen
- Earth’s early atmosphere consists of carbon dioxide, with some water vapour, nitrogen, and traces of methane and ammonia
- the water vapour condensed as the Earth cooled and rain fell, forming oceans
- comets also brought water
- bacteria first appeared
- algae and other life forms evolved. they could make their own food using the sun’s energy, with oxygen being their waste
- oxygen levels rise steadily as algae and bacteria fill the seas
- animals evolved using oxygen to respire
- our atmosphere today
what is the ozone layer made up of?
oxygen
describe the carbon cycle:
- 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
what was required for animals to exist?
- a temperature decrease
- a CO2 decrease
- the appearance of O2
- the ozone layer
- the formation of oceans
what are two main points about the Earth’s atmosphere and its ozone layer?
- 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
