Studied by 0 people
Looks like no one added any tags here yet for you.
for 200 million years…..
the proportions of diff gases in the the atmosphere have been much the same as they are today
The proportions of different gases in the atmosphere- nitrogen
about four-fifths (approximately 80%) nitrogen
The proportions of different gases in the atmosphere- oxygen
about one-fifth (approximately 20%) oxygen
The proportions of different gases in the atmosphere- other gases
small proportions of various other gasws- including carbon dioxide, water vapour and noble gases
why is evidence for earth’s early atmosphere limited
due to the time scale of 4.6 billion years so theories have changed over time
one theory suggests that during first billions of years
there was intense volcanic activity that released gases that formed the early atmosphere
like water vapour- as the earth cooled water vapour condensed to form oceans
volcanoes also released a lot of carbon dioxide- also small amounts of methane and ammonia- and nitrogen which gradually built up
at start of period atmosphere was most like mars or venus today- mainly CO2 and little to no O2
CO2 dissolved in water and carbonates were precipitated producing sediments, reducing amount of CO2 in atmosphere
how oxygen increased in the atmosphere
photosynthetic plants in sea 2.7 billion years ago- algae and plants
photosynthesis produced oxygen
plants evolved meaning more O2 could be produced- reached point where animals could evolve
photosynthesis also takes in CO2- carbon trapped in fossil fuels
how long does it take fossil fuels to form
millions of years
are fossil fuels non renewable or renewable
non renewable- if we keep using them, they will run out
how is coal formed
from remains of ferns and trees
if they die in marshy wetlands then they don’t decompose- due to lack of O2 and acidic conditions- both prevent decomposition from happenening
over time plants are covered by sedimentary rocks- the pressure and high temp creates coal
how is oil formed?
crude oil is formed from plankton who were covered by mud on sea bed- if O2 isnt present then they don’t decompose
over time, they are compressed by sediment
heat and pressure convert them into crude oil
how is natural gas formed??
mainly the hydrocarbon methane, often find natural gas near deposits of oil
natural gas formed in similar way as oil- crude oil
examples of greenhouse gases
water vapour, methane and carbon dioxide
Amount of water vapour in the atmosphere….
..varies widely and changes depending on the temp
How the greenhouse effect works?
Energy from the sun travels to the earth as short wave radiation e.g. ultra violet & visible light
Some of radiation reflects back into space but most pases through easily as short wavelength radiation doesnt interact strongly with gas molecules
Energy of radiation is absorbed when it reaches the surface of earth
Surface of earth now radiates the energy as long wavelength radiation e.g. infra red
Some of LWR interacts with greenhouse gas molecules- energy in LWR is absorbed- as energy trapped in atmosphere causes temp to increase
Why is the greenhouse effect key?
Keeps temp warm enough to support life
Without greenhouse effect, the earth would be too cold for most living organisms to survive
are the levels of CO2 and methane increasing/decreasing and why?
levels are increasing due to human activity
Why are CO2 levels increasing??
burning of fossil fuels
What do we use coal for and what does it produce?
for electricity, produces CO2
What do we use petrol & diesel for and where does it come from??
power cars
Came from burning fossil fuels producing CO2
What do we use natural gas for and where does it come from??
heat our homes
Came from fossil fuels, burnt to produce CO2
Where is CO2 normally absorbed from??
growing trees
Why have the levels of CO2 being absorbed decreased?
rainforests are being destroyed by deforestation
Why is deforestation occuring and how??
forests burned to supply land for burning cattle
Release large amounts of CO2
Why is temp of atmosphere increasing?
More of the energy from the sun is trapped
Effects of rising temps
melting of polar ice sheets and glaciers
Lead to more severe weather
change distribution of animals
Effects of rising temps- melting of ice
leads to rising sea levels- flooding of low lying areas
Effects of rising temps- severe weather
storms in the uk
Effects of rising temps- distribution of animals
such as insects—> may change distribution of insect borne diseases e.g. malaria
What do scientists believe climate change is caused by?
human activity which causes release of greenhouse gases
Evidence for climate change
Shared between many different scientists- can criticise the evidence and share if its valid- peer review
Problems with sharing findings of climate change
complex and difficult to model
see stories on the media that’re simplified or having bias- scientists must work hard to communicate ideas to general public
uncertainties
Carbon footprint
Gives us an idea pf how much something contributes to climate change
Amount of CO2 and other greenhouse gases emitted over the full life cycleof a product
Reducing CO2 emissions- energy
lot of energy used to heat our homes- often comes from burning fossil fuels
Insulate our homes or turn down heating
Reducing CO2 emissions- cars
great deal of CO2 released from driving our cars
Reduce by using public transport- less CO2 per passenger
Reducing CO2 emissions- electricity
produced by burning fossil fuels
reduce by switching to renewable forms of energy
reduce how much electricity u use at home e.g. energy saving bulbs or turn off plugs when not being used
Problems with reducing CO2 emissions
most of solutions are expensive and people are reluctant to pay
Some are inconvenient
Reducing methane emissions
biggest source are agriculture
grazing cattle release methane when they pass wind, one way is to reduce intake of meat
another source is landfills- can reduce by trapping methane n burning it to produce electricity
methane is much more powerful than CO2
Problems with reducing methane emissions
people enjoy eating meat and are unlikely to change diet
trapping and burning methane costs money
Pollutants from fuels
CO2
water vapour
carbon monoxide
sulfur dioxide
oxides of nitrogen
When do fuels release energy?
when they’re combusted e.g. coal & hydrocarbons
coal used to generate electricity in power stations
hydrocarbon used to power vehicles
What do most fuels include??
including coal and hydrocarbons
Contain carbon and hydrocarbons
What happens when we burn fuels?
Carbon and hydrogen are oxidised
Complete combustion occurs when we’ve made CO2
Requires a lot of oxygen
Where do we find the hydrocarbon methane?
In natural gas and used to heat homes
What happens if oxygen is limited when combustion occurs?
produces carbon monoxide instead dioxide
Carbon monoxide characteristics
toxic gas with no colour or smell
people have detectors in their homes
What do SOME fuels contain??
contain element sulfur
e.g, coal
What happens when coal is burned?- sulfur
Sulfur atoms are oxidised that produces gas sulfur dioxide- sulfur + oxygen —> sulfur dioxide
Where are oxides of nitrogen produced?
produced in engines- high temps cause
N2 + O2 —> NOx
What can sulfur dioxide and oxides of nitrogen cause??
cause breathing problems
form acid rain
Acid rain
Damage trees, corrode buildings made from limestone
Particles of carbon (soot) are called?
Particulates
What can particulates and unburned hydrocarbons cause?
Can damage human health- increase risk of heart/lung disease
Reduce amount of energy from sun reaching surface- earth—> global dimming (affect rainfall patterns)
