Liquid fuels easy to handle, store and transport. They occupy less space. The combustion is cleaner and has higher colourific value than solid fuels. However, they are more expensive. They produce unpleasant smell if the combustion is incomplete.
Mining and fractional distillation of crude petroleum (boiling pointwise separation only)
Mining of petroleum oil
The crude oil is present deep below the impervious rocks in earth’s crust; the oil layer is covered by a layer of natural gas floats over a layer of brine. Mining is done by drilling holes in earth’s crust and sinking pipes up to the oil-bearing porous rocks. Oil usually gushes out itself due to the hydrostatic pressure of the natural gas. It may also be mechanically pumped by using suitable pumps.