Chemical changes

• Metals that react with oxygen to form metal oxides

  • Chromium
  • Copper
  • Iron
• Extraction of metals and metal oxides

  1. Heating the metal with carbon

  2. Carbon removes the oxygen from the metal oxide
• Metals are found in the ground as metal oxides


  The metal needs to be extracted
• Reactivity series of metals

  • Potassium
  • Sodium
  • Calcium
  • Magnesium
  • Aluminium
  • Zinc
  • Iron
  • Tin
  • Lead
  • Copper
  • Silver
  • Gold
  • Platinum
• Oxidation


  Gain of oxygen and loss of electrons
• Reduction


  Gain of electrons
• A chemical reaction where both oxidation and reduction occur is a redox reaction
• Copper sulfate + Zinc


  Zinc sulfate + Copper
• Cu2+ is reduced, Zn is oxidised
• Metals + Acids


  Metal salt + Hydrogen
• Metal carbonates + Acids


  Metal salt + Carbon dioxide + Water
• Acids + Alkalis


  Metal salt + Water
• Neutralisation


  The acid used determines the salt produced in a reaction
• Salts produced from acids

  • Chlorides (from hydrochloric acid)
  • Nitrates (from nitric acid)
  • Sulfates (from sulfuric acid)
• Neutralisation reaction


  NaOH + HCl → H2O + NaCl
• Soluble salts


  • Can be made from acids by reacting them with carbonates or solid insoluble substances such as metal oxides or hydroxides
• Making a pure, dry sample of a soluble salt

  1. Add excess solid to acid until no more reacts

  2. Filter off excess solid to produce a solution

  3. Crystallise the salt solution to produce solid salt
• Hazards, risks and precautions when making a soluble salt
• Acid


  Produces H+ ions in water, tastes sour, turns blue litmus paper red, corrodes metals
• Alkali


  Produces OH- ions in water, tastes bitter, turns red litmus paper blue
• Strong acid


  Completely ionised in aqueous solution (e.g. hydrochloric, nitric, sulfuric acids)
• Weak acid


  Only partially ionised in aqueous solution (e.g. ethanoic, carbonic, citric acids)
• As pH decreases by 1 unit


  Hydrogen ion concentration increases by a factor of 10
• Electrolyte


  A liquid or solution containing free-moving ions that can conduct electricity
• Electrolysis


  1. Positive ions move to the negative electrode (cathode)

  2. Negative ions move to the positive electrode (anode)
• Products of electrolysis


  • At cathode: metal or hydrogen
  • At anode: oxygen or halogen
• Rules for determining products of electrolysis