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History
Fossil fuels are the remnants of plants and animals that died around 300 million years ago. As their remains became covered in topsoil, and the recycling action of the earth's crust moved their remains further and further underground, the remains came under immense pressure and heat. The result is a hydrocarbon-dense material that takes three main forms: coal (a rocklike fossil fuel), oil or petroleum (a liquid fossil fuel) and natural gas (a gaseous fossil fuel).
Coal was discovered in ancient China 3,000 years ago and was used for a variety of purposes such as heating homes and metalworking. Oil or petroleum has seeped to the surface through cracks in the crust called "fissures." The oil that made it to the surface was called "pitch" or "tar" and was used to seal early boats and canoes as well as for warfare where it was set on fire and poured onto enemies as early as Roman times. Natural gas also seeps to the surface where it may be ignited by certain atmospheric conditions or may just dissipate harmlessly into the atmosphere.
Significance
Fossil fuels are particularly significant because they are packed with easy-to-burn hydrocarbons. Hydrocarbons are molecules that are composed entirely of chains of carbon and hydrogen, which is a method for storing energy. Burning fossil fuels produces a lot of heat very quickly. This capacity for heat is measured in British thermal units, or BTUs. Wood, which was traditionally used to heat homes for centuries in Europe and America, has a BTU range of between 2,000 and 5,000 BTU per pound of material. Coal, on the other hand, has between 4,000 and 15,500 BTU per pound of material, depending upon the type of coal used.
Function
Fossil fuels are oxidized through the application of heat, which acts as a catalyst to the exothermic chemical reaction known as combustion. When a fossil fuel is placed in a heated environment, its molecules are excited to the point that they burn, which is the severing of the electrical bonds between the hydrogen and carbon atoms. The hydrocarbon reacts with the oxygen in the air during combustion, forming water vapor (H2O) and carbon dioxide (CO2). If not enough heat is applied to the combustion, then the result is a lot of free carbon molecules in the form of soot. High-heat environments provide ample energy to allow the breaking of hydrocarbons into water and carbon dioxide in larger amounts.
Effects
Petroleum, as it comes out of the ground, is ill-suited for use as a high-energy fuel and therefore must be refined. Refining increases the length of the hydrocarbon molecules to the point where it becomes a very energy-packed liquid. One gallon of typical gasoline has 125,000 BTU of thermal energy stores within it. The small explosions inside the engine (called combustion) power cars, trucks, airplanes, ships and other machines used in daily American life. As a result, gasoline allows for the cheap, efficient transportation of goods and people over vast distances.
Benefits
Heating via fossil fuels, such as natural gas, is also more efficient than other methods of heating. Natural gas is forced under pressure through a series of tubes into a furnace (or oven in some cases). The gas is forced out of small nozzles that are regulated by mechanical or electronic means. Natural gas has 1,027 BTU per square foot of gas, but considering most natural gases are lighter than air, natural gas is sold in 100,000 BTU units, called therms. Natural gas is relatively cheap to produce (or in some cases, capture) and can be generated by humans and human society (methane from garbage decomposition or coal mining, for example), which makes it a renewable resource, though it may not technically be considered a "fossil fuel" anymore.