Chemical changes

• Acids have a low pH, Alkalis have a high one
• Phenolphthaleine - colourless in acid, pink in alkali
• litmus - red in acid, blue in alkali
• Methyl orange - red in acid, yellow in alkali
• H+ is acidic, OH- is alkaline
• Practical

  heat acid in water bath to speed up reaction

  Add base to acid. This will make soluble salt. Excess solid will sink

  Filter excess solid

  Heat solution

  Leave to cool and crystalise

  Filter
• Metal + Acid = salt + hydrogen

  Acid + Alkali = salt + water
• Negative - anion. Gain

  Positive - cation. Loss

  PANIC - positive annode negative is cathode
• Electrolysis breaks down a substance using electricity. Current is passed through an electrolyte (molten or dissolved compound) causing it to decompose
• OIL RIG

  Oxidation is loss of electrons, Reduction is gain.
• positive ions (cations) move towards the cathode (negative electrode) and reduced
• negative ions (anions) move towards the anode (positive electrode) and are oxidised
• as ions gain/lose electrons they form uncharged substances and are discharged from the electrolyte
• metal is discharged at the cathode and non metal is discharged at the anode

  eg. aluminium at cathode and oxygen at anode
• electrolysis is more expensive than reduction

  carbon is cheap, electricity is not