Metals

• Metals are found on the left and the middle of the periodic table
• Metals are rocks found in the earths crust that can be extracted and used as a material.
• The most unreactive metals are silver and gold and they are found as elements in the rocks. They are not chemically bonded to other elements in the compound.
• Zinc, iron and copper are all found as compounds within rocks. They are generally found bonded to oxygen as compounds called metal oxides
• The word equation for the reduction of zinc oxide with carbon is: zinc oxide + carbon --> zinc + carbon monoxidee
• When metals are above carbon in the reactivity series, they cannot be extracted using reduction with carbon. Carbon is not reactive enough to take the oxygen away from the metal
• Corrosion happens when a metal continues to oxidise. The metal becomes weaker over time, and eventually all of it may become metal oxide.
• Metals can oxidise in air. They react with oxygen and form metal oxides.
• Rusting is a specific example of corrosion, which occurs when iron or steel reacts with oxygen and water:
• An iron or steel object only rusts if oxygen and water are present.
• Rusting can be prevented by creating a physical barrier to oxygen and water. Ways to do this include:

  • painting
  • oiling and greasing
  • coating with plastic
• iron can be protected from rusting if it is in contact with a more reactive metal, such as zinc. The more reactive metal oxidises more readily than iron, so it ‘sacrifices’ itself while the iron does not rust.
• Galvanising

  When iron is coated in zinc, the process is called galvanising. The zinc layer stops oxygen and water reaching the iron. Zinc is more reactive than iron, so it also acts as a sacrificial metal. This protection works, even if the zinc layer is scratched.
• An alloy is a mixture of two or more elements, where at least one element is a metal. Many alloys are mixtures of two or more metals.
• Converting pure metals into alloys often increases the strength of the product
• Solid metals have a regular lattice structure. When a force is applied to a metal, layers of atoms can move past each other. The more difficult it is for the layers to move, the more force is needed and the stronger the metal.
• The reactivity series of metals is a chart listing metals in order of decreasing reactivity. In general, the more reactive a metal is, the more vigorously it reacts with other substances.
• We can examine the reactivity of metals by observing their reactions with water, steam and acid.
• When a metal reacts with water, a metal hydroxide and hydrogen are formed.
• Sodium reacts vigorously with water.

  sodium + water ➞ sodium hydroxide + hydrogen
• Calcium reacts readily with water.

  calcium + water ➞ calcium hydroxide + hydrogen
• Calcium hydroxide is slightly soluble in water so once the solution is saturated, it starts to become milky as solid calcium hydroxide appear.
• Magnesium reacts very slowly with water. However, it reacts vigorously with steam:

  magnesium + steam → magnesium oxide + hydrogen
• Metals which react with steam form the solid metal oxide and hydrogen gas.
• When metals react with acid hydrogen gas is produced.

  The general equation is:

  Metal + Acid → Salt + Hydrogen