autumn test

• Changes of state - boiling and evaporating are changes of state from a liquid to a gas.
• Rusting - the chemical name for rusting is hydrogen iron oxide.
• What is the scale that represents how reactive metals are?


  The reactivity series.
• Displacement reaction - when a more reactive metal takes the place of a less reactive metal in a compound.

  example

  silver nitrate + copper = copper nitrate + silver

  this is because carbon is more reactive than silver, so when silver is added to copper the carbon displaces it.
• What is a mixture?


  2 or more separate substances that aren't joined together with chemical bonds.
• What methods can separate mixtures?

  Filtration, distillation, chromatography, evaporation.
• carbon and hydrogen can be used to extract metals from their compounds using a displacement reaction.
• Reduction - the loss of oxygen .

  Oxidisation - the gain of oxygen.
• Carbon is the reducing agent in a reaction.
• What are the 4 stages of sewage treatment:

  • screening and grit removal
  • primary sedimentation
  • secondary sedimentation
  • biological treatment
• sewage - the term given to any waste water.
• Screening and grit removal - sewage water is passed through a metal grid to trap larger objects.
• Primary sedimentation- small pieces of solid sediment will sit at the bottom of the container and be remove through pipes, this is called sludge.
• Biological treatment - water still contains harmful substances so bacteria is added to digest any harmful microorganisms or toxic chemicals.
• Secondary sedimentation - the remaining bacteria sat at the bottom of the container is removed . the remaining effluent (waste water) can be sterilised and used as drinking water.
• What is potable water?

  Water that is safe to drink.
• How do we make potable water?

  • screening - water is passed through a metal grid.
  • Filtration- through a bed of fine sand and gravel.
  • Sterilising - using chlorine to kill harmful microorganisms.
• Sea water can be passed through a membrane to make potable water.
• Pure and potable

  • if something is pure it contains only one type of atom or molecule
  • if something is potable it means safe to drink - not necessarily pure.
• What does the water cycle do?

  the water cycle provides fresh water for plants and animals on land before draining into the seas.
• Rusting occurs when iron reacts with oxygen in the presence of water.
• Sustainable development - is development that meets the needs of current generations without compromising the ability of future generations to meet their own needs.
• A composite- is made of two or more materials with different properties.
• Most composites are made of two materials:

  a. a matrix which surrounds and binds together fibres or fragments of the other material

  b. a reinforcement.
• The assessment is broken into the following stages:

  • extracting and processing raw materials.
  • manufacturing and packaging
  • use and maintenance during its lifetime
  • disposal at the end of its useful life.
• Desalination -The process of removing salt.