5.1+Unit+2+Fossil+Fuels

=__**What are fossil fuels?**__=

====**Fossil fuels are [|fuels] formed by natural processes such as [|anaerobic decomposition] of buried dead [|organisms]. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years.**====

=__**Types of fossil fuels**__=

1. Petroleum 2. Coal 3. Natural Gas


 * Petroleum:** Also called crude oil, the term petroleum encompasses multiple types of hydrocarbons, which are compounds consisting primarily of hydrogen and carbon but possibly containing other elements as well. Petroleum forms mainly from marine vegetation and bacteria that lived in the oceans or other saltwater environments millions of years ago. Petroleum deposits are often found in the same locations as natural gas, each of which can be extracted for energy production. Petroleum is used in the production of plastic and medications among many other products.


 * -Coal:** Coal forms from plants such as ferns, moss and trees which lived near shorelines and in swamps and bogs millions of years ago. When these plants die, they are slowly covered with sediment and over time pressed deep into the earth where they are affected by mounting heat and pressure. Under these conditions, the organic matter becomes richer in carbon and hydrogen, and increasingly deprived of oxygen. Coal goes through various stages of development based on its increasing carbon content, and coal containing higher levels of carbon burns cleaner than those with lower levels. The purest form of coal is graphite, which consists almost entirely of carbon.


 * -Natural Gas:** Natural gas forms mainly from the remains of plankton, or a type of small water organisms including algae. Consisting mostly of methane, natural gas is often found on top of deposits of petroleum due to its lower density, and is extracted in the same process. However, deposits containing only natural gas do exist. Natural gas is desirable in part because it burns cleaner than coal and petroleum. Natural gas is commonly used in residential applications for home heating and has a myriad of other applications.