OCR AS Chemistry (F321.4) - Resources Revision Notes

These revision notes are for Resources - the fourth module of F322 (Organic Chemistry) from OCR AS Chemistry A.

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OCR AS Chemistry Notes
THE GREENHOUSE EFFECT
Without greenhouse gases, planet would be a lot colder
o Hence average temperatures of Venus and Mars
THE GREENHOUSE EFFECT
1. Incoming visible light is unaffected by the gases in the earth's atmosphere
2. Some is reflected by the earth and the atmosphere but most of this radiation is absorbed by the earth's surface and
warms it
3. Infra-red radiation is then emitted from the earth's surface
4. Some of the radiation passes through atmosphere and some is absorbed and re-emitted in all directions by
greenhouse gas molecules
o This warms the earth's surface and lower atmosphere
Greenhouse effect creates an equilibrium
o Surface and gases absorb energy at same rate as radiation steady temperature
GREENHOUSE GASES
1) WATER VAPOUR
a. Evaporation of lakes and oceans
2) CARBON DIOXIDE
a. Volcanic eruptions
b. Animal respiration
c. Burning or decay of organic matter
3) METHANE
a. Production of coal, natural gas and oil
b. Product of rotting organic waste in landfill
c. Released from certain animals during digestion
d. Trapped under ice-like structures in cold northern seas
o Greater contribution to greenhouse effect
The bonds in the gases absorb infra-red radiation

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This causes the molecule to vibrate
Eventually the molecule will emit some of this energy as radiation
This radiation can then be absorbed by another greenhouse gas or the earth's surface
GWP =
o Global Warming Potential
o Ability of a trace gas to cause global warming
o Chlorofluorocarbons (CFCs) are 25000 times more efficient at absorbing infra-red than carbon dioxide, but
since they have been banned, their effect is diminishing
GLOBAL WARMING
Ice and permafrost melting
Antarctic ice sheet melting
Tropical areas have more…read more

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The hydrogen is burnt, producing only water
STORAGE AS CARBONATES
Store carbon in stable minerals by reacting CO2 with metal oxides to produce stable carbonates
o C aO (s) + C O2 (g)CaCO3 (s)
o M gO (s) + C O2 (g)MgCO3 (s)
However natural reaction is very slow
o Efforts to increase it are very energy intensive (power station needs 60-180% more energy)
USES OF CO2
FOAM
CFCs once used
CO2 now used to produce expanded polystyrene etc.…read more

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Produces natural fizz in beer
Supercritical CO2 can be used to extract the flavour of beer from hops
DRY CLEANING
Previous solvents are toxic
Used with a wetting agent, CO2 is a safer solvent that still dissolves grease
TOXIC WASTE TREATMENT
Remove toxic chemicals from waste
CHEMICAL SYNTHESIS
Can be used as wither a solvent or reagent
Because of ability to control solvent properties, products can be obtained with fewer wasted bi-products
AIR POLLUTION
1) CARBON MONOXIDE
a.…read more

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USING RENEWABLE RESOURCES
a. Plant-based substances
b. Solar energy instead of fossil fuels (eventually run out)
2) SAVING MONEY
a. Not having to treat hazardous waste
b. Using fewer chemicals
c. Using less energy
3) PREVENTING WASTE
a. Time + money is not spent on clearing it up
4) MAXIMISING ATOM ECONOMY
a. Designing synthetic methods to maximise all materials used in process into final product
5) RECYCLING AND BIODEGRADABILITY
a. At the end of their use, products should be recycled
b.…read more

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