topic c4- chemical changes

• acids

  • solution with pH lower than 7
• acids

  form H+ ions in water
• alkali

  solution with pH higher than 7
• alkali

  form OH- ions in water
• bases

  any substance that will form a salt when reacted with acid
• water + metal

  metal hydroxide + hydrogen
• acid + metal

  salt + hydrogen
• neutralisation reactions

  • acid + base -> salt + water
  • acid + metal oxide -> salt + water
  • acid + metal hydroxide -> salt + water
  • acid + metal carbonate -> salt + water + carbon dioxide
• • metal oxides, metal hydroxides + metal carbonates are base
  • so all produce salt + water with acid
  • neutralisation reaction
• salts

  • sulphuric acid creates sulphates
  • nitric acid creates nitrates
  • hydrochloric acid creates chlorides
• potassium most reactive

  sodium

  lithium

  calcium

  magnesium

  aluminium

  CARBON

  zinc

  iron

  HYDROGEN

  copper

  silver

  gold least reactive
• redox reactions

  electrons are transferred
• oxidation

  • loss of electrons
  • gain of oxygen
• reduction

  • gain of electrons
  • loss of oxygen
• electrons

  O xidation

  I s

  L oss

  R eduction

  I s

  G ain
• cathode

  negative electrode
• anode

  positive electrode
• electrolysis

  • molten ionic compounds are entered into the container, this is the electrolyte
  • the positive metal ions are attracted to the cathode where they gain electrons, become neutral and sink
  • the negative ions are attracted to the anode and lose electrons and rise
• displacement reaction

  a reaction in which a more reactive metal or non-metal will take the place of another in an ionic compound
• electrolysis- anode

  • attract negative ion
  • lose electrons
  • oxidation
• electrolysis- cathode

  • attract positive ions
  • gain electrons
  • reduction
• products at anode

  • oxygen gas when there are no halogens present
  • if halogens present, halogen gas will form instead
• products at cathode

  • if the metal is more reactive than hydrogen, hydrogen gas will form
  • if the metal is less reactive than hydrogen, the metal is deposited (forms a solid)