8.3 Metals and their Reaction with Oxygen

• • most metals react with oxygen when they get hot enough
  • some metals react quickly without even being heated
  • sodium, potassium, and calcium appear dull from the container, but when pieces are cut, the surface is shiny
  • the shiny surface will soon become dull again after reacting with oxygen (the oxide of the metal)
  • these metals are stored under oil to prevent them from reacting with water vapour in the air.
• • when a metal reacts with oxygen, the product is a metal oxide
  • word equation: metal + oxygen - metal oxide
  • silver reacts slowly with the air, and goes black over time as silver oxide is formed
  • some metals, such as gold, do not react with oxygen. They are unreactive/inert (unreactive)
• Reactivity of metals:

  Most reactive - least reactive

  • potassium
  • sodium
  • calcium
  • magnesium
  • aluminium
  • carbon
  • zinc
  • iron
  • tin
  • lead
  • hydrogen
  • silver
  • gold
  • platinum
• The reactions between iron and oxygen

  • when iron is left in damp air, it rusts
  • the iron reacts with oxygen to form an orange-brown solid, called iron-oxide
  • word equation: iron + oxygen - iron oxide
  • this reaction only takes place when both water and oxygen are present but the water is not written into the equation
  • not a useful reaction because this could mean a building collapsing
• What causes iron to rust

  • Iron cannot have water and oxygen if you want to prevent it from rusting
  • calcium chloride can be used to absorb moisture in the air
  • iron can be protected by painting to stop oxygen in air from reaching the iron
  • also can be galvanised (covering the iron with a layer of zinc)