How is the chemical energy contained in fossil fuels converted to electrical energy in an electric power station?
Chemical energy contained in the fossil fuels undergo combustion which is an exothermic reaction and heat is evolved. The more heat evolved, the better the fuel is.
That heat is used to boil water and the resultant steam is used to rotate a wheel which is connected to the axle of an electric generator. This way, electric power is generated from fossil fuels.