chemistry of the atmosphere

• percentage of gases in earths atmosphere - dry air (no water molecules)

  * nitrogen - 78%

  * oxygen - 21%

  * carbon dioxide - 0.04%

  * argon - 0.9%

  * other gases - 0.06%
• how much water vapour can air contain (%)

  up to 5%
• when was the earths early atmosphere

  4.6 billion yers ago
• how did the early atmosphere evolve

  1 ) a lot of volcanic activity so atmosphere mainly made up of co2 and a bit of h2o, ch4, nh3, n2 - earth was very hot so no animal or plant life

  2 ) planet cooled so water vapour condensed to form oceans

  3 ) bacteria and algae evolved and then photosynthesised to produce oxygen

  4 ) co2 starts to decrease

  5 ) other gases decrease and some increase
• how does co2 start to decrease in the early atmosphere

  1 ) photosynthesis

  2 ) sedimentary rocks take it in - dead sea matter builds up at bottom of ocean and forms rocks like limestone

  3 ) fossil fuels - some remains of these organisms become fossil fuels
• why does methane decrease

  methane + oxygen = carbon dioxide + water
• why does ammonia decrease

  ammonia + oxygen = nitrogen + water
• why does nitrogen increase

  * inert / very unreactive

  * build up over time
• how does the greenhouse effect work

  1 ) sun heats up earth with infrared radiation / heat

  2 ) some reflected back into space off atmosphere

  3 ) some infrared radiation absorbed by earths surface

  4 ) molecules of greenhouse gases absorb infrared radiation on its way out, “trapping” it in the earths atmosphere
• adv v dis of greenhouse effect

  adv : if didn’t exist, earth would be too cold for life to form

  dis : increasing levels of greenhouse gases mean that scientists believe it is heating up earth too much
• human activity - co2

  1 ) burning fossil fuels

  2 ) deforestation - reduces planets capacity to absorb co2

  3 ) oceans became less able to absorb co2 - rising
• human activity - ch4

  1 ) swamp

  2 ) grazing cattle

  3 ) landfill

  4 ) rice fields / decomposing waste
• why do people not believe humans are impacting climate change

  atmosphere temperature fluctuates
• evidence of climate change (levels of co2 and temp increase)

  air pockets in ice cores
• what type of radiation is absorbed by greenhouse gases

  long wavelength radiation (infrared / heat)
• how does long wavelength cause global warming

  1 ) absorbed by greenhouse gases

  2 ) make bonds in molecules vibrate, bend and stretch more vigorously

  3 ) this raises the temperature as heat is trapped is trapped in the atmosphere
• what are the main greenhouse gases

  h2o - water vapour

  co2 - carbon dioxide

  ch4 - methane
• how much is the atmosphere temperature meant to rise in the next 100 years

  increase 5.8 degrees
• 4 main effects of global change

  1 ) rising sea levels = flooding

  2 ) more frequent and extreme weather events

  3 ) changes to temp and rainfall - affects food production and how different countries grow food

  4 ) stress of ecosystems
• what is the carbon footprint

  total amount of co2 and other greenhouse gases emitted over a full life cycle of a product, service or event
• ways to reduce carbon footprint

  1 ) carbon capture - pump co2 into ground (expensive)

  2 ) plant based diet - reduce demand for beef and lowers transport

  3 ) insulate homes

  4 ) reforestation

  5 ) use alternative energy resources
• what are atmospheric pollutants


  substances that contaminate the air making it harmful or damaging for human health or the environment
• source of atmospheric pollutants


  factories

  lorries

  cars
• examples of atmospheric pollutants

  water vapour - already in air

  carbon dioxide - already in air

  sulfur dioxide

  nitrogen oxides

  carbon monoxide

  carbon particulates

  unburnt hydrocarbons
• what how does incomplete combustion occur - hydrocarbons

  burning hydrocarbons and fuels with longer chains
• how is water vapour produced

  1 ) combustion of alkenes

  2 ) incomplete combustion
• why is water vapour an atmospheric pollutant

  greenhouse gas - contributes to global warming
• how is co2 produced

  combustion
• why is co2 an atmospheric pollutant

  greenhouse gas - contributes to global warming
• how is carbon monoxide produced

  incomplete combustion
• why is carbon monoxide an atmospheric pollutant

  * colourless odourless gas

  * binds to haemoglobin in instead of oxygen, taking its place

  * starves body of oxygen
• how are carbon particulates produced

  incomplete combustion
• how are carbon particulates an atmospheric pollutant

  * small particles of solid carbon

  * global dimming - no photosynthesis

  * damage cells in our lungs

  * cause cancer
• when are unburnt hydrocarbons released

  alongside carbon monoxide or carbon particulates
• how is nitrogen oxide produced

  * nitrogen and oxygen in air react

  * very high temperatures in car engines - combustion

  1 ) no2

  2 ) no3
• how is nitrogen oxide an atmospheric pollutant


  * cause breathing and respiratory problems (asthma)

  * acid rain
• how is sulfur dioxide produced

  sulfur impurities in fuel react with oxygen
• how is sulfur dioxide an atmospheric pollutant

  * acidic gas

  * acid rain - damage trees and buildings and harms wildlife
• prevention of the formation of sulfur dioxide

  * remove sulfur from fuels before burning

  * acidic so2 can be neutralised at factories or power stations