Chemistry 3_ water.txt

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Author:
jpopat
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155530
Filename:
Chemistry 3_ water.txt
Updated:
2012-05-23 17:33:49
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chemistry water
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AQA chemistry 3
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    • author "me"
    • tags ""
    • description ""
    • fileName "Chemistry 3: water"
    • freezingBlueDBID -1.0
    • Tap water contains....
    • Dissolved substances e.g. calcium and magnesium (in hard water)
  1. What is the difference between hard and soft water?
    Hard water has more dissolved Ca and Mg
  2. Water can be used...
    • As a solvent
    • A coolant
    • In industrial processes
  3. Main points of the water cycle:
    ENERGY from the sun makes water EVAPORATE. It CONDENSES to form clouds. Temperature drops, RAIN falls onto land. RUNOFF accumulates back in the sea.
  4. What does soluble mean?
    A solid that dissolves on water
  5. The solid that dissolves in water is called....
    Solute
  6. Why is water called a universal solvent?
    Many substances dissolve in it
  7. Solubility is measured in...
    g/100g of water
  8. Soluble or insoluble: most ionic compounds...
    Soluble
  9. Soluble or insoluble: most covalent compounds
    Insoluble
  10. Soluble or insoluble: some molecular substances
    Soluble
  11. How does temperature affect solubility of compounds?
    Increased temperature means increased solubility
  12. Explain HOW temperature effects solubility of compounds.
    Liquid expands when heated so there is more room in there for solid particles
  13. What does a solubility curve show?
    The maximum amount of solute that can be dissolved in a solvent at a particular temperature to give a SATURATED SOLUTION
  14. What happens if a saturated solution cools down?
    Some solute crystallises out
  15. How can you work out how much solute cryatallises out?
    Solute at initial temp - solute at 'cooled down' temp = solute that crystallises out.
  16. Solubility of gas increases as......
    • Temperature decreases
    • Pressure increases
  17. Explain HOW solubility of gases is effected.
    When liquids are heated they expand so it is easier for gases to escape
  18. Give an example of when CO2 is used
    In fizzy drinks under pressure. Opening the lid releases pressure which is why it would eventually go flat (gas would escape)
  19. What gas dissolved in water is essential for aquatic life?
    Oxygen
  20. Give an example of how, related to water, power stations harm aquatic life.
    The discharge of hot water means less oxygen can dissolve in the water in lakes so there is less oxygen for the aquatic life.
  21. List the two main stages of drinking water
    • The water is passed through a FILTER BED to remove solid particles
    • CHLORINE GAS is added to kill harmful bacteria
  22. How can water quality be improved?
    • Using a filter which contains carbon, silver and ion exchange resins.
    • Any water can be distilled but this used a lot of energy which makes it more expensive.
  23. What type of water readily forms a lather with soap?
    Soft
  24. How do compounds get in hard water?
    Water flows over rocks and compounds get dissolved in the water
  25. Hard water with soap forms....
    Scum. This makes it harder to form a lather.
  26. Advantages of hard water
    Good for your health
  27. Disadvantages of hard water
    • More soap is needed for lather, increases COST
    • Deposits (scale) form on appliances e.g. kettles. This reduces efficiency.
  28. List the two ways to remove hardness
    • Add sodium carbonate
    • Ion exchange column
  29. Explain why sodium carbonate solution removes hardness
    The carbonate ions react with the Ca and Mg (which make water hard) to make calcium carbonate and magnesium carbonate (respectively). These are both insoluble precipitates.
  30. Explain what an ion exchange column does to remove hardness of water.
    The resin supplies hydrogen or sodium ions. As the hard water passes through the Ca and Mg ions are replaced by the H or Na ions.

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