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• Acid + metal


  Salt + hydrogen
• Acid + insoluble base


  Salt + water
• Acid + alkali (soluble base)


  Salt + water
• Acid + metal carbonate


  Salt + water + carbon dioxide
• Fuel cells


  Hydrogen is the fuel, reacts with oxygen to produce an electric current, and the only chemical product is water
• As long as the hydrogen fuel is supplied they will never stop working
• They are more expensive than chemical cells (what you know as batteries)
• They do not need to be repaired or replaced
• Chemical cells


  Eventually the chemicals run out so the cell loses voltage and then stops working, then you have disposal issues
• Chemical cells are cheaper
• Fuel cells can be used to drive cars
• Advantages of fuel cells

  • No carbon dioxide produced so no impact on global warming
  • Fuel cell motors are very quiet and have less moving parts so are more reliable
• Disadvantages of fuel cells

  • Hydrogen is flammable and hard to store safely, also a gas so needs compressed to store a decent amount
  • There are a lack of places to fill up with hydrogen (or petrol/diesel is readily available)