6.2 Production of energy
A fuel is a substance used to obtain energy. Burning fuels (like oil, coal etc.) to form oxides is an exothermic reaction (gives out heat). The heat from burning fuels is used in power plants to create steam from water and turn turbines.
Hydrogen: Burns explosively with oxygen, so it is used in rockets. But in a fuel cell it combines with oxygen without burning (details of the construction and operation of a fuel cell are not required).
Nuclear fuels: are not burned. The radioisotopes (unstable atoms) decay naturally giving out energy. In a nuclear power station they are forced to break down by shooting neutrons at them. They heat up water to make steam which turns turbines. Advantages: lots of energy is made from a small amount of fuel and no carbon dioxide is produced. Disadvantage is that it produces radiation and radioactive waste, non-renewable
Electrochemical cell: consists of a negative pole (the more 
reactive metal) and a positive pole (less reactive metal) and an electrolyte. The greater the difference in reactivity of the two metals, the greater the voltage will be. The electrons flow because one metal is more reactive, so it has a stronger drive to give up its electrons. The atoms give up electrons and enter the solution as ions.
