chemical changes

• Metal extraction


  The process of obtaining metals from their ores
• Reduction


  The loss of oxygen in a chemical reaction
• Oxidation


  The gain of oxygen in a chemical reaction
• Some metals, like gold, are so unreactive that they are found as pure metals in the Earth's crust and can be mined
• Most metals exist as compounds in rock and have to be extracted from the rock
• Ore


  A rock or mineral from which a metal can be extracted profitably
• Extracting less reactive metals

  Reduction with carbon
• Extracting more reactive metals

  Electrolysis
• Oxidation


  A substance gains oxygen in a reaction
• Reduction


  A substance loses oxygen in a reaction
• Oxidation and reduction reactions

  • iron + oxygen ➞ iron oxide
  • iron oxide + carbon ➞ iron + carbon dioxide
• Salt


  A compound where the hydrogen from an acid has been replaced by a metal
• Acids


  • hydrochloric acid
  • sulfuric acid
  • nitric acid
• Ions formed in acid solutions

  • H+ and Cl-
  • 2H+ and SO4^2-
  • H+ and NO3-
• Types of salts formed

  • metal chloride
  • metal sulfate
  • metal nitrate
• Sodium salts


  • sodium chloride, NaCl
  • sodium sulfate, Na2SO4
  • sodium nitrate, NaNO3
• Reactions of metals with water and acids depend on the reactivity of the metal
• Reactivity series


  • potassium
  • sodium
  • lithium
  • calcium
  • magnesium
  • aluminium
  • zinc
  • iron
  • tin
  • lead
  • copper
  • silver
  • gold
• Reactivity


  How chemically reactive a metal is
• Extraction methods


  • electrolysis
  • reduction with carbon
• Oxidation


  The loss of electrons
• Reduction


  The gain of electrons
• Writing ionic equations


  1. Check symbol equation is balanced

  2. Identify all aqueous ionic compounds

  3. Write those compounds out as ions

  4. Remove spectator ions
• Half equation


  An equation showing half of an ionic equation, either the oxidation or reduction half
• A metal's reactivity depends on how readily it forms an ion by losing electrons
• Displacement reaction


  A more reactive element takes the place of a less reactive element in a compound
• Displacement reaction


  • copper sulfate + iron ➞ iron sulfate + copper
• Acid


  A compound that, when dissolved in water, releases H+ ions
• Alkali


  A compound that, when dissolved in water, releases OH- ions
• pH scale


  A measure of acidity and alkalinity, running from 1 to 14
• Indicator


  A substance that can show if something is an acid or an alkali
• Acids react with some metals to form salts and hydrogen gas
• Neutralisation reactions


  1. Acids react with metal hydroxides to form salts and water

  2. Acids react with metal oxides to form salts and water

  3. Acids react with metal carbonates to form salts, water, and carbon dioxide
• Strong acid


  An acid that is completely ionised in water
• Weak acid


  An acid that is only partially ionised in water
• Concentrated acid


  An acid with lots of acid dissolved in a small volume of water
• Dilute acid


  An acid with little acid dissolved in a large volume of water
• Strong acids


  Acids that, when dissolved in water, every molecule splits up into ions - they are completely ionised
• Strong acids


  • H2SO4(aq) ➞ 2H+(aq) + SO4^2−(aq)
  • HNO3(aq) ➞ H+(aq) + NO3^−(aq)
  • HCl(aq) ➞ H+(aq) + Cl^−(aq)
• Weak acids


  Acids where only a percentage of their molecules split up into ions when dissolved in water - they are partially ionised