chemical changes

• the lower the pH of a solution, the more acidic it is
• the higher the pH of a solution, the more alkaline it is
• the pH of a neutral substance is 7
• alkalis would show up as purple on a universal indicator
• acids would show up as red on a universal indicator
• neutral substances would show up as green on a universal indicator
• acids and bases neutralise each other
• acid + base -> salt + water
• acids produce protons in water
• strong acids ionise completely in water
• weak acids do not fully ionise in a solution
• electrolysis means splitting up with electricity
• electrolysis

  1. electric current is passed through an electrolyte (a molten or dissolved ionic compound) and the ions move toward the electrodes where they react and the compound decomposes
  2. positive ions in the electrolyte will move towards the cathode and gain electron (they are reduced)
  3. negative ions in the electrolyte will move towards the anode and lose electrons (they are oxidised)
  4. this creates a flow of charge through the electrolyte as ions travel to the electrodes
  5. as ions gain or lose electrons, they form the uncharged element and are discharged from the electrolyte
• an ionic solid cannot be electrolysed because the ions are in fixed positions and cannot move
• molten ionic compounds can be electrolysed because the ions can move freely and conduct electricity