OCR 21st Century Science, Chemistry - C1

• The earth is surrounded by a thin layer of gases called the atmosphere which contain:
  • 78% - Nitrogen (N2)
  • 21% - oxygen (O2)
  • 1% - Argon (Ar) and other noble gases
  • 0.04% - Carbon Dioxide (CO2)
  • 0-4% - Water vapour (varies according to weather conditions)
• The earth's atmosphere id just 1km thick while the diameter is over 12 000km.
• the earth is heated by the sun but at the same time the earth also radiates heat back out as infrared energy. the earth's greenhouse gases (methane [CH4], Carbon dioxide [CO2], Water Vapour [H2O]) absorb the heat to stop it from escaping into space. So the earth is warmer then it would be.

• Sulphur Dioxide (SO2) - causes acidic rain which kills plants and water creatures.
• Carbon Monoxide (CO) - A poisonous gas which reacts with blood.
• Nitrogen Dioxide (NO2) - causes acidic rain, causes breathing problems, makes asthma conditions worse.
• Particulates - make things dirty, make lung infections worse, makes asthma worse.

• Units used for measurement are PPB(parts per billiion) or PPM (parts per million).
• Measurements can vary because:
  • Varibles - factors that change
  • Measuring equipment has a limited digree of accuracy
  • the user's skill of accuracy
• Chemicals - atom -> element -> Molecules.

• For a complete combustion all the reactants must be present with the right amount needed to make the products.
• Incomplete combustion happens when there is a shortage of an element that is needed to make the product.

Photosynthesis Formulae

Water(H2O) + Carbon Dioxide(CO2) -----> Oxygen(O2) + Glucose(C6H12O6)

• Carbon dioxide enters the atmosphere by:
  • Burning fossil fuels
  • Humans breathing out
  • Respiration
  • Land use
• Carbon dioxide is removed from the atmosphere by:
  • Photosynthesis
  • Dissolves in ain water and sea water
  • Some is stored in Limestone

• Emissions from power stations can be reduced by:
  • Using less energy so less fuel is burned
  • Using a filter system to remove Sulphur dioxide and particulates from flue gases before they leave a coal burning power station.
  • Removing toxic chemicals before they are burned.
  • Using alternative renewable energy sources like solar, wind, hydroelectric energy instead of fuels.
• Emissions from motor vehicles can be reduced by:
  • Buying a car with a modern engine that burns less fuel.
  • Buying a hybrid car which uses electric power in the city centre and can change to petrol for longer journeys,
  • Using a low sulphur fuel to reduce the amount of sulphur dioxide released.
  • Converting the engine to run on biodiesel, a renewable fuel.
  • Using public transport so there are less vehicles on the road.
• A catalytic converter chances a harmful chemical and changes it into a less harmful chemical without itself being effected.