Fuel fuel. They are also used to start a coal fire. Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid. Most liquid fuels in widespread use are derived from the fossilized remains of dead plants and animals by exposure to heat and pressure inside the Earth's crust. However, there are several types, such as hydrogen fuel (for automotive uses), ethanol, jet fuel and bio-diesel which are all categorized
Fossil fuel be found in hydrocarbon fields either alone, associated with oil, or in the form of methane clathrates. The theory that fossil fuels formed from the fossilized remains of dead plants by exposure to heat and pressure in the Earth's crust over millions of years was first introduced by Andreas Libavius “in his 1597 Alchemia [Alchymia]” and later by Mikhail Lomonosov “as early as 1757 and certainly by 1763”.. The first use of the term "fossil fuel" was by the German chemist Caspar Neumann, in English translation in 1759. The United States Energy Information Administration estimates that in 2007 the world's