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2012-06-14 13:05:17

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  1. disposable nappies for babies need to absorb as much wate as possible . Disposable nappies have a pad containing a special polymer called hydrogel . Hydrogels absorb water . Suggest one disadvanatge of for the company if it increases the amount of hydrogel in its nappy pads
    • any one from
    • costs more
    • uses more energy
    • uses more resources
  2. explain what happened to most of the water vapour in the earths early atmosphere
    it condensed to form the oceans
  3. explain the meaning of locked up carbon dioxide
    • any two from
    • •(CO2) from the atmosphere
    • • (CO2) taken in millions of years ago or early (atmosphere)
    • •(CO2) was used to form the shells / skeletons of marine organisms / fossil fuels
  4. what is a compound
    a substance that contains 2 or more different types of atoms from different elements that are chemically joined
  5. suggest two ways in which a limestone quarry is of benifit to people
    • it provides local jobs for people
    • they can use limestone in products such as bathroom tiles
  6. how can you tell , safely that heat is produced in a reaction
    the water has been formed is a gas
  7. nitrogen oxides are prodyced when petrol burns in a car engine . State one condition needed for these compounds to form
    there needs to be a very high temperature generated by the engine so that nitrogen and oxygen from the air can react
  8. describe two ways in which the amount of sulphur dioxide released into the atmosphere may be reduced
    • we can use biodiesel instead of burning fossil fuels to generate our electricity
    • the SO2 produced can be reacted with CaO
  9. what is global dimming and how is it caused
    it is the amount of sunlight we have lost per decade due to particulates released during incomplete combustion of fuels . These particles reflect sunlight back into space . Also water droplets also condense around clouds making them more reflective than usual
  10. what is the problem with methane as a fuel compared to hexane as a fuel
    methane is more difficult to store ans transport
  11. describe at least 2 disadvantages of using ethanol or hydrogen in cars instead of hydrocarbon fossil fuels such as petrol
    • hydrogen is difficult to store and transport , it also uses processes such as electrolysis to make it which uses fossil fuels
    • if we use ethanol produced by fermentation of sugars then agricultural land will be destroyed perhaps leading to food shortages and more expensive food pirces
  12. explain why the amount of benzene allowed in petrol is limited by law
    because benzene is toxic
  13. cracking is a thermal decomposition reaction , what happens in thermal decomposition reactions
    a substance is broken up into two or more different substances by heating it and passing the hot vapour over a catalyst
  14. what are alkenes made in cracking used to make
  15. why was the parrafin soaked in ceramic wool
    to keep the liquid at the end of the tube
  16. 1) why are the first few bubbles of gas not collected
    2) describe a test you could do to prove that alkenes have been produced . Give the results of the test 
    • 1) air (this is the air that was origionally in the test tube before the parrafin vapourised)
    • 2) we coud add bromine water to the alkenes .The alkene would decolourise the bromine 
  17. Crude oil is a very important raw material with many uses . Give some social and economic advantages and disadvantages of using products from crude oil as fuels or as raw materials for plastic and other chemicals . (6)
    • advantages
    • * produces useful fuels
    • * used to make raw materials that are converted into useful amterials e.g. plastics/solvents/medicine
    • * fuel has been relatively cheap
    • disadvantages
    • * non renewable
    • * more recently crude oil has become much more expensive
    • * when burned it produces carbon dioxide which causes global warming and sulphur dioxide that causes acid rain  
  18. describe how sunflower oil is extracted in 8 points (4)
    • seeds are harvested 
    • seeds are crushed
    • water is added to the crushed seeds
    • the mixture is pressed
    • water and sunflower are obtained
    • water and sunflower oil seperate into two layers
    • water and other impurities are removed
    • sunflower oil is collected  
  19. explain what happens to the carbon-carbon double bonds during hardening (1)
    the carbon-carbon double bonds are opened up forming single carbon-carbon bonds 
  20. describe two benifits of and a drawback of cooking food with vegetable oils rather than with water (3)
    • advanatges 
    • * vegertable oils have higher boiling points than water , so can be used to cook foods at a higher temperature 
    • * it gives food a pleasant flavour
    • disadvanatge
    • * it increases the energy we get fromm eating our foods and this will make us fat if we dont burn off the energy 
  21. an emulsion is a 
    mixture of oil and water in which droplets of one liquid are disperesed in another
  22. Rb is in group 1 how will it react with water ?
    Rb will react violently with water , giving off hydrogena and forming rubidium hydroxide 
  23. write a balanced chemical equation for the reaction of sodium with oxygen 
    4Na + O ===> 2Na2O
  24. write the word equation and the balanced symbol equation for the reaction potassium with water 
    • potassium + water ===> potassium hydroxide + hydrogen 
    • 2K + 2H2O ===> 2KOH + H2
  25. Sodium and potassium are stored in oil . Why do you think that is ?
    To stop them reacting with oxygen or moisture in the air 
  26. Kr is in group 0 . Describe its likely properties 
    unreactive gas 
  27. explain why argon is used in filament light bulbs
    argon is unreactive so the white hot filament will not react with it , so will not burn out 
  28. explain why the noble gases remained undiscoverd for so long 
    no active properties to be discovered , so finally only discovered by default - a part of air that wouldnt react
  29. hydrogen is cheaper to produce than industrially than helium . A nitrogen/oxygen mixture comes free in the air . So why do we fill pary ballons with helium instead of cheaper hydrogen and fill deep sea divers' tanks with an expensive helium/oxygen mixture instead of cheaper compressed air ? 
    Both hydrogen and helium are lighter than air gases but helium is unreactive , whereas hydrogen could catch fire/explode . Nitrogen in air dissolves in the blood and causes health problems . Insoluble helium doesn't