GCSE Chemistry

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GCSE Chemistry
2012-06-14 15:20:05

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  1. explain what happened to most of the water vapour in the earths early atmosphere (2)
    • condensed
    • to form the oceans/sea 
  2. explain the meaning of "locked up carbon dioxide" (2)
    • any two from:
    • • (CO2) from the atmosphere
    • • (CO2) taken in millions o fyears ago or early (atmosphere)
    • • (CO2) was used to form the shells / skeletons of marine organisms / fossil fuels
  3. suggest two ways in which a limestone quarry may harm the environment (2)
    • it means wildlifes natural habitats will be destroyed to make way for the quarry
    • causes noise and dust pollution  
  4. Balance this equation for the combustion of propane 
    C3H+ O===> H2O + CO2
    C3H8 + 5O===> 4H2O + 3CO2
  5. nitrogen oxides are produced when petrol burns in a car engine . State one condition needed for these compounds to form (1)
    nitrogen oxides are formed when the nitrogen and oxygen in the air react due to very high temperatures prdouced by the engine 
  6. describe two ways in which the amount of sulphur dioxide released into the atmopshere may be reduced (2)
    • the sulphur dioxide can be reacted with calcium oxide 
    • we can burn less fossil fuels by using biodiesel instead  
  7. what is global dimming and how is it caused ? (3)
    the amount of sunlight we have lost per decade due to solid particlues due to incomplete combustion of fuels . These particles reflect sunlight back into space . Also water droplets condense aroun them making clouds more reflective than normal 
  8. gloabl dimming is likely to have reduced the 
    impact of global warming 
  9. what extra information does a displayed structual formula give compared with a molecular formula (1)
    unlike a molecular formula it tells use where the double and single bonds are
  10. state two ways in which carbon dioxide is added to the atmopshere (2)
    respiration and burning fossil fuels
  11. what are tectonic plates (1)
    interlocking pieces of rock in the upper mantle and crust
  12. explain why mountians are formed on plate boundaries (2)
    because here two plates meet and the crust is pushed upwards
  13. describe the older theory that explained how mountians formed as the earth cooled
    the crust shrank and wringled forming mountians
  14. scientists think that the movement of plate is caused by convection currents , about how far are the plates moving each year (1)
    • 1-10 cm
    • but in exam say 6cm
  15. why were Wenger's ideas not accepted when he first put them forward (1)
    he could not explain how the continent moved and scientists had other theories like the landbridge theory
  16. why is it important to monitor underground water levels in earthquake zones (2)
    changes i water levels could help predict an earthquake and save lives as people could be evacuated
  17. outline how insoluble compounds can become part of sedimentary rocks (2)
    • they sink to the bottom of the sea as sediment
    • over millions of years these sediments formed sedimentary rocks such as limestone , locking away the carbon in rocks
  18. outline how soluble compounds can be used by marien organisms and become part of sedimentary rock (3)
    soluble compounds such as calcium hydrocacrbonate were used by sea creatures to make calcium carbonate shells . As these creatures died , their shells fell into the sediment . Over time , these sediments formed sedimentary roks , such as limestone locking away the carbon in rocks
  19. explain and evaluate the effects of human activities on the atmopshere (6)
    • * humans burn large amounts of fossil fuels
    • ==> increases the amount of carbon dioxide in the atmopshere which causes global warming
    • ==> increases the amount of sulphur dioxide and nitrogen oxides in the atmosphere which cause acid rain
    • ==> increases the amount of carbon particulates in the atmosphere which cause respiration problems
    • ==> increases the amount of carbon monoxide in the atmopshere which is toxic
    • we also cause deforestation which means that there are less trees to absorb carbon dioxide so the concentration of carbon dioxide in the atmosphere increases
  20. to what extent would you agree that it is important to burn fuels in a good supply of air ? In your answer conatin the products of complete and incomplete combustion
    • if the fuels contains sulfur the air supply makes little difference because sulphur dioxide is still produced in partial combustion , which causes acid rain .
    • If the air supply is low carbon monoxide is produced which is toxic . If the supply is good however carbon dioxide will be produced , which is a greenhouse gas
  21. explain how the air in a blast funace helps to raise the temperature
    more oxygen , therefor faster burn and faster energy output
  22. write a balanced symbol equation for the extraction of iron oxide using a blast funace if iron oxide = Fe2O3
    2Fe2O3 + 3C ===> 4Fe + 3CO2
  23. explain why copper cannot be extracted from a 1% copper ore in a blast furnace
    too much waste - it would clog it up and be inefficient
  24. explain the production of copper from low grade ores by leaching
    the copper would be soaked in acid or water and the copper compounds would be leached out and we would remove the copper from the leachate by electrolysis
  25. can you suggest a method for cleaning up rivers polluted with copper salts ? explain how it works . are there any possible disadvantages to the method ?
    put scrap iron in the river to displace copper . the solid copper metal is not harmful and may be removed . Iron goes into the solution rather than the copper . Iron is not so harmful . Possible disadvanatges include unsightliness if teh iron is dumped directly into the river , percipitated copper and dissolved iron potentially affecting the ecosystem , and impurities in the scrap iron causing other forms of pollution