Chemical Change

• Metals by reactivity


  • Most reactive
  • Less reactive
• Metals above carbon in reactivity series

  • Need electrolysis to be extracted
• Metals below carbon in reactivity series


  • Can be extracted by reduction
• Unreactive metals


  • Generally found in earth as pure ores, unreacted with anything
• Reactive metals


  • Generally found combined with oxygen as metal oxides
• Metal more reactive than hydrogen


  Hydrogen gas produced in electrolysis
• Metal less reactive than hydrogen


  Something else produced as gas in electrolysis
• More reactive metal


  Displaces less reactive metal in a reaction
• Less reactive metal


  Cannot displace more reactive metal in a reaction
• Oxidation


  Loss of electrons
• Reduction


  Gain of electrons
• Anode


  Positive electrode
• Cathode


  Negative electrode
• Balancing half-equations in electrolysis


  1. Balance elements

  2. Make charge neutral by adding electrons

  3. Determine if oxidation or reduction
• Acid + metal = salt + hydrogen
• Metal oxide + acid = salt + water
• Acid + metal hydroxide = salt + water
• Acid + metal carbonate = salt + water + carbon dioxide
• Making copper sulfate


  1. Heat sulfuric acid

  2. Stir in copper oxide until in excess

  3. Filter to remove excess copper oxide

  4. Evaporate to leave copper sulfate crystals
• pH scale


  1 is acidic, 7 is neutral, 14 is alkaline
• Acidity


  Caused by hydrogen ions
• Alkalinity


  Caused by hydroxide ions
• Acid-base titration


  1. Pipette alkali into flask

  2. Add acid from burette drop by drop

  3. Stop when indicator changes colour permanently
• Strong acids


  • Hydrochloric, nitric, sulfuric, hydrobromic, hydroiodic, chloric
• Strong acid


  Fully dissociates into ions
• Weak acid


  Partially dissociates into ions
• Concentration of strong/weak acid


  Affects degree of dissociation into ions
• Electrolysis


  Requires molten or dissolved ionic compounds
• Aluminium electrolysis


  1. Positive anode attracts oxygen, forming oxygen gas

  2. Negative cathode attracts aluminium ions, forming aluminium metal
• Common electrolysis setups


  • Sodium chloride
  • Sodium sulfate
  • Copper chloride
  • Copper sulfate
• Products of electrolysis depend on reactivity of metals
• Hydrogen test


  Squeaky pop
• Oxygen test


  Relights glowing splint
• Chlorine test


  Bleaches damp litmus paper
• Types of bases


  • Metal oxides
  • Metal hydroxides
  • Metal carbonates
• Neutralization reactions


  Reactions between acids and bases
• Making soluble salts using an insoluble base


  1. Place dilute acid in beaker and heat gently

  2. Add insoluble base a little at a time

  3. Filter out excess base

  4. Evaporate solution to get crystals

  5. Filter and dry crystals
• Acid reacts with metal oxide or hydroxide


  Forms salt and water
• Acid reacts with metal carbonate


  Forms salt, water and carbon dioxide
• Soluble salts are formed when an acid reacts with an insoluble base