gases in the atmosphere

• label

  A) nitrogen

  B) 78

  C) oxygen

  D) 21

  E) argon

  F) 0.9

  G) co2

  H) 0.04

  
• • Scientists know the historic composition of the air by analysing the tiny air bubbles trapped in ice cores taken at the poles
  • The air bubbles were trapped as the snow and ice was laid down tens of thousands of years ago and provide a snapshot of what our atmosphere was like back then
• finding percentage of oxygen

  • react a metal / non-metal with oxygen in a fixed volume of air
  • eg burn a phosphorus in a bell jar that's sitting in a trough of water
  • Initially the water levels are the same inside and outside the jar
  • As the phosphorus burns it uses up the oxygen inside the bell jar and the water level rises
  • By making careful measurements of water levels before and after the experiment you can determine the percentage of oxygen in the air
  • Phosphorus is very suitable for this experiment as it burns readily until all the available oxygen is used up
  • phosphorus is toxic
• label

  A) bung

  B) bell jar

  C) evaporating dish

  D) trough

  E) water

  F) phosphorus

  G) burning

  H) volume

  
• label

  A) stopcock

  B) iron filings

  C) air

  D) inverted

  E) water

  
• finding % o2

  1. draw a mark on the burette and fill water up to the lower mark
  2. let it drain into a small measuring cylinder
  3. measure the volume of water
  4. add a little water to moisten the inside of the burette
  5. close the tap and sprinkle iron filings / iron wool into the bottom of the burette
  6. add a little water to moisten the inside of the burette
  7. invert into a trough of water n record position of water level
  8. after 3-4 days note new position

  
• combustion ( burning )

  • oxygen reacting with elements / compounds to produce oxides
  • exothermic
  • oxidation reaction
• label

  A) white flame

  B) white

  C) powder

  D) oxide

  E) exothermic

  F) water

  G) blue flame

  H) colourless

  I) poisonous

  J) gas

  
• co2 from thermal decomposition

  • thermal decomposition - reactions where a substance breaks down due to the action of heat
  • eg thermal decomposition of metal carbonates
  • carbonates of metals from the lower half of the reactivity series tend to decompose on heating to produce the metal oxide and carbon dioxide gas
  • metal carbonate -> metal oxide + carbon dioxide
• • The thermal decomposition of copper (II) carbonate occurs readily on heating
  • Copper (II) carbonate is a green powder and slowly darkens as black copper (II) oxide is produced
  • The carbon dioxide given off can be tested bypassing the gas through limewater and looking for it to turn milky
  • CuCO (s) → CuO (s)+CO (g)
  • copper (II) carbonate →copper (II) oxide + carbon dioxide

  A) heat

  
• The release of carbon dioxide from calcium carbonate in the production of cement is a contributing source of rising atmospheric CO2 levels that contributes to the enhanced greenhouse effect.
• GREENHOUSE EFFECT

  • When shortwave radiation from the sun strikes the Earth’s surface it is absorbed and re-emitted from the surface of the Earth as infrared radiation
  • Much of the radiation, however, is trapped inside the Earth’s atmosphere by greenhouse gases which can absorb and store the energy
  • Carbon dioxide, methane and water vapour are gases that have this effect
  • Increasing levels of carbon dioxide, although present in only a small amount, is causing significant upset to the Earth’s natural conditions by trapping extra heat energy
  • This process is called the enhanced greenhouse effect
• label

  A) atmosphere

  B) energy

  C) absorbed

  D) surface

  E) re-emitted

  F) longer

  G) infrared

  H) heat

  I) space

  J) absorbed

  K) greenhouse

  L) re-emitted

  M) trapped

  N) atmosphere

  O) hotter

  
• Carbon dioxide Sources:

  1. Combustion of wood and fossil fuels
  2. respiration of plants and animals
  3. thermal decomposition of carbonate rocks and the effect of acids on carbonates
• It is important to understand the difference between the greenhouse effect and the enhanced greenhouse effect. The greenhouse effect ensures the mean global temperature is around 15 C and without greenhouse gases the surface of the Earth would swing between extreme heat and extreme cold. The enhanced greenhouse effect, due an increase in greenhouse gas concentrations, most scientists believe, is leading to global warming.