Chemical species are known to contain chemical energy. Chemical energy is contained in chemical bonds in a chemical substance.
Since energy can neither be created nor destroyed, energy contained in chemical bonds can be transformed from one form to another. Coal contains chemical energy.
One of the ways of generating electricity is the combination of fossil fuels. This involves the conversion of chemical energy to heat energy. The steam produced is used to turn a turbine. The turning off the turbine implies a conversion of heat to mechanical energy. The turning of the turbine now produces electrical energy.
