C10-Using resources

• Creating potable water through filtration and sterilisation (from fresh water)

  -For filtration, a mesh or permeable separator of some sort is used to get rid of any materials or larger particles in the water, along with a sand/gravel filter.

  -For sterilisation, chlorine gas can be bubbled through the water to neutralise any acidic particles or using ultraviolet light to kill bacteria.
• Desalination

  -By ‘reverse osmosis’ using a semi-permeable mebrane

  -By distillation
• Why is it impractical to use methods like reverse osmosis and distillation to desalinate large quantities of water?

  These processes use a lot of energy, and are therefore very expensive.
• Distillation of water

  -Test the pH of the water; if it isn’t close to neutral enough ,it must be neutralised using an acid/alkaline.

  -Test water for presence of sodium chloride; test for sodium using a flame test and test for chlorine using dilute nitric acid and silver nitrate solution (chlorine present= white precipitate).

  -Pour water into distillation apparatus and heat it so that it boils, and forms steam, leaving any dissolved salts in the flask.

  -Retest the water’s pH and for sodium chloride
• pure/potable water

  Pure water: pH is always 7, contains no dissolved substances

  Potable water: pH is not always 7, contains dissolved substances (little enough so it is safe to drink)
• Testing for pure water

  -Check the pH of the water; if the pH isnt 7, it definetely isnt pure, and if pH is 7, it may be pure.

  -Test for the presence of dissolved substances; Weigh the water and heat it gently in an evaporating basin.

  -If the water has gained weight after evaporation, it isnt pure (the dissolved substances have formed crystals at the top of the basin)

  -If no change in weight has occurred, the water is likely to be pure.
• Common resources from the earth that humans use

  -Water (for drink and to use as energy)

  -Materials like cotton (for fabric and clothes)

  -Fossil fuels (for combustion)

  -Crops/ plants from agriculture (produces food and can also be used as fuel or for construction)
• Efficient methods of taking resources from the earth

  -Using alternatives to fossil fuels that are renewable and do not harm the environment

  -Bioleaching to efficiently extract metals

  -Artificial fertilisers for crops so we can produce more food with the land we already have available for agriculture

  -Using chemistry to make more available water potable
• Water waste management (1)

  -Sewage water screening using a mesh to filter through larger materials and solids.

  -Water is then sent to large sedimentary tanks, where effluent and sludge is produced.

  -The sludge can then be taken away and digested by anaerobic bacteria so that it can be used as things like fertiliser for plants.

  -The effluent is also extracted ,but must be treated to get rid of harmful chemicals (aerobic bacteria digest harmful microorganisms and chemicals).

  -The effluent can then be discharged into fresh water.

  -Remaining water can be desalinated to make it potable.
• When is waste-managed water used as potable water

  in places where water is scarce
• Easy/cheaper method to make water potable

  Treating groundwater from aquifiers with chlorine to neutralise its pH (groundwater already has a low amount of dissolved substances)
• Alternative methods of extracting metals

  -Bioleaching

  -Phytomining
• Phytomining

  -Plants are grown on land that contains metal ores

  -Plants absorb the metal from the ores and concentrate it

  -Plants are harvested and burned, the ash contains high amounts of metal compounds

  -The metal from the ashes are extracted by reduction by carbon or electrolysis
• Bioleaching

  -Bacteria are mixed with low grade ores

  -The bacteria carry out chemical reactions and produce leachate solution

  -Leachate solution contains the metal compounds from the ores, which can be extracted by reduction by carbon or electrolysis
• Advantages of alternative methods to extract metals

  -Extract low grade ores economically

  -Tend to produce much less waste and pollution during extraction and processing in comparison to traditional mining (sustainable)
• Stages of a life cycle assessment

  -Extraction/sourcing

  -Transportation

  -Processing

  -Usage

  -Disposal and storage