Chemistry Using Resources (T10)

• What is potable water?

  Water that is safe to drink.
• What is pure water?

  Water that only contains H2O
• Potable water contains dissolved substances such as dissolved salts and microbes
• What are composites?

  Composites are materials made from two or more different types of substances embedded together.
• Some examples of composites are:

  • Fiberglass - glass embedded in polymers (plastics)
  • Carbon Fiber - Long chains of carbon atoms bonded together
  • Concrete - aggregate (fragments of materials) embedded in cement
  • Wood- cellulose fibres
• What is the equation for corrosion?

  Iron + oxygen + water —>hydrated iron (III) oxide
• Both air and water are needed for iron to rust.
• What are the three main ways to prevent rusting?

  • Painting/coating with plastic
  • Electroplating - used to coat the iron with a layer of different metal that won’t be corroded
  • Oiling/Greasing - when moving parts are used etc bike chain.
• What are ceramics?

  Non-metal solids with high melting points that aren’t made from carbon compounds.
• Some ceramics can be made from clay. Its ability to be moulded when wet and then hardened makes clay ideal for making pottery and bricks.
• Glass is a ceramic which can be made by heating a mixture of sand, sodium carbonate and limestone
• What are low grade ores?

  Ores without a lot of copper.
• What are the two methods of extracting low grade ores?

  Bioleaching

  Phytomining
• What is bioleaching?

  Bacteria are used to convert copper compounds in the ore into soluble copper compounds, separating the copper. The leachate (solution produced) contains copper ions which can be extracted by electrolysis or displacement.
• What is phytomining?

  Growing plants in soil that contains copper so the plants can’t use it and therefore it gradually builds up in the leaves. The plants can be harvested, dried and burned so the ash contains soluble copper compounds from which copper can be extracted by electrolysis or displacement.
• What are the four stages of a life cycle assessment?

  1. Getting the raw materials
  2. Manufacturing and packaging
  3. Using the Product
  4. Product Disposal
• What are the problems with life cycle assessments?

  1. It takes account of the person carrying out the assessment and therefore it can be biased
  2. Selective LCAs show some of the impacts and not all so it gives them positive advertising
• What are three stages of making potable water?

  Finding an appropriate fresh water source

  Filtration

  Sterilasation
• In filtration, a wire mesh removes larger wastes such as twigs. The gravel and sand beds filter out any other solid particles.
• In sterilisation, the bacteria is sterilised by bubbling chlorine gas, using ozone or UV light.
• Why might some hot countries use desalination instead?

  In hot countries there’s not enough surface or groundwater (low rainfall).
• What is desalination?

  Removing seawater through distillation or reverse osmosis
• What is reverse osmosis?

  The sea water moves from a low to high concentration (reverse) through a membrane which traps ions and larger molecules, allowing only water molecules to pass through.
• How can you test and distil water in the lab?

  1. Test the pH of the water using a pH meter to make sure it’s between 6.5 and 8.5.
  2. Pour salty water into a distillation apparatus and heat the flask. The water will boil and form steam, leaving any dissolved salts in the flask
  3. The steam will condense back to liquid water in the condenser.
  4. Retest the pH of the water
• What is waste water?

  Sewage and toilet water etc.
• Desalination requires a lot of energy and is very expensive
• Sewage treatment process:

  • Sewage is screened to remove large substances
  • Sedimentation in a settlement tank: heavier suspended solids sink to the bottom to produce sludge, while lighter effluent floats on top
  • Effluent is treated by biological aerobic digestion: air is pumped to encourage aerobic bacteria to break down organic matter
  • Sludge is transferred to large tanks for anaerobic digestion by bacteria
  • Anaerobic digestion breaks down organic matter in the sludge, releasing methane gas (energy source) and producing waste that can be used as fertilisers
• What is the haber process?

  Used to make ammonia from hydrogen and nitrogen
• What is the equation for making ammonia?

  Nitrogen + Hydrogen --> Ammonia

  N2 3H <— 2NH3
• What conditions are required for the Haber process?

  • High temperature 450 degrees
  • High Pressure: 200 atmospheres
  • Iron catalyst
• The ammonia (gas) cools in the condenser and liquifies so it can be removed. The unused hydrogen and nitrogen are recycled so nothing is wasted.
• Because the reaction is reversible, some of the ammonia converts back into hydrogen and nitrogen. Eventually it reaches a dynamic equilibrium.
• Why is high pressure used in the haber process?

  High pressure increases the yield of ammonia and the rate of reaction.
• Why is a high temperature used in the haber process?

  Even though it would decrease the yield of ammonia, a high temperature is used to increase the rate of the reaction.
• NPK fertilisers are used to increase crop yield, growing faster and bigger.
• What does NPK stand for?

  Nitrogen, Phosphorus, Potassium