Chemistry

• Air


  Mixture of gases: Nitrogen 78%, Oxygen 21%, Carbon dioxide 0.03% and inert gases 0.9%
• Fractional distillation of air

  1. Air is cooled or compressed until it turns into a liquid

  2. Liquid air is allowed to warm up and various gases boil off at different temperatures/boiling points

  3. The gases are released and stored in gas cylinders
• Carbon dioxide and water vapour must be removed because they solidify and block pipes of fractionating column at low temperatures
• Removing carbon dioxide


  Using sodium hydroxide (forms sodium hydrogen carbonate) or potassium hydroxide
• Removing water vapour


  Using drying agents like calcium chloride (hygroscopic)
• Finding volume and percentage of oxygen in air

  1. A known volume of air is passed over a heated metal

  2. The metal removes oxygen from air by forming a metal oxide
• Reaction of copper with oxygen

  • Cu + O2 heat-> CuO
• When copper is heated in air, it slowly reacts with oxygen forming Copper (ii) oxide. In the experiment, 100 cm³ of air was passed between two gas syringes.
• Uses of oxygen


  • Used by sea divers and mountain climbers for respiration
  • Treatment of sewage
  • Combustion/burning of fuels
  • Steel manufacturing
  • In hospitals after accidents
  • Welding
• Uses of carbon dioxide

  • By plants during photosynthesis
  • Making fizzy drinks
  • For softening dough (fermentation)
• Normal concentration of carbon dioxide gas on earth


  Very important because it traps Infrared rays (IR) and keeps the earth warm
• If the concentration of carbon dioxide gas and other green house gases is too high, a lot of heat is trapped. This may result in over heating of the earth. Excessive heating of the earth is called global warming.
• Causes of increased carbon dioxide concentration

  • Burning fossil fuels
  • Deforestation
  • Cars-use fuel
  • Industries
• Air pollution


  Introduction of gaseous contaminants into the environment
• Major pollutants of air

  • Carbon
  • Carbon monoxide (CO)
  • Oxides of sulphur (SO2, SO3)
  • Oxides of nitrogen (NO2, NO)
  • Lead compounds
  • CFCs (chlorofluorocarbons)
• Carbon


  • Dust particles from coal mines can reflect light and prevent it from reaching the ground if they are on air. This may reduce the rate of photosynthesis and kill plants.
• Carbon monoxide (CO)


  Toxic - It replaces Oxygen gas in haemoglobin forming Carboxyhaemoglobin hence, reduces the amount of oxygen supplied to the cells.
• Do not start the car and leave it running for a long time in closed garage or house.
• Oxides of sulphur (SO2, SO3)


  They dissolve in rain water then cause ACID RAIN because they are acidic oxides.
• Effects of acid rain


  • Corrode buildings made up of calcium carbonate
  • Lowers the pH of water in lakes and rivers the kill water animals like fish
  • Leaching of nutrients
• Oxides of nitrogen (NO2, NO)

  NO2 is an acidic oxide hence it causes acid rain<|>NO destroys the ozone layer because it is a very reactive gas
• Lead compounds


  Affects the development of brain (intelligence)<|>Very poisonous/toxic
• CFCs (chlorofluorocarbons)


  Destroy the ozone layer
• Ozone layer (O3)


  Protects the ground/earth from dangerous ultraviolet ray (UV) which cause skin cancer
• Methods of preventing air pollution

  1. Use catalytic converters in car exhausts

  2. Use unleaded petrol

  3. Use long chimneys in industries to reduce amount of SO2, SO3 deposited on the ground

  4. Remove sulphur from fuels before they burn

  5. Neutralise the acidic oxides by reacting them with carbonates

  6. Convert the oxides to useful solutions like sulphuric acid

  7. Use catalytic converters in car exhausts for oxides of nitrogen

  8. Recycle plastics
• Complete the table below:
• Organic compound


  A compound that contains carbon
• Metal carbonates, carbon dioxide and carbon monoxide are not included in organic compounds
• Hydrocarbon


  A compound that contains only hydrogen and carbon atoms

  
• Hydrocarbons undergo complete and incomplete combustion
• Complete combustion


  Excess oxygen, water and carbon dioxide form
• Incomplete combustion


  Insufficient oxygen, carbon monoxide and water or carbon and water form
• Prefix


  Tells you how many carbon atoms are present in the longest continuous chain
• Suffix


  Tells you what functional group is on the compound
• When there is more than one carbon atom where a functional group can be located, the carbon atoms are numbered to describe where the functional group is
• When 2 functional groups are present, 'di-' is used as a prefix to the second part of the name
• Branching also needs to be considered, the carbon atoms with the branches are described by their number
• The functional group takes precedence so it has the lowest number when describing the location of functional groups and branches
• Unbranched organic compounds


  • Alkanes
  • Alkenes
  • Alcohols
  • Carboxylic acids

  
• Methane is the main constituent of natural gas