High School Earth Science: Earth’s Energy - Non-renewable Energy Resources — Flashcards

Oil, or petroleum, is a liquid fossil fuel. It is currently the single largest source of energy in the world. When oil first comes out of the ground, it is called crude oil. It is a thick, dark brown or black liquid. It forms from the remains of tiny organisms that live at the sea surface and then sink to the seafloor when they die, forming layers of deposits. As the layers pile up, heat and pressure increase. Over millions of years, the dead organisms turn into liquid oil.    
Crude oil is a mixture of many different hydrocarbons. To separate the different hydrocarbons, crude oil must be broken down, or refined, in plants called refineries. Refining is possible because each hydrocarbon in crude oil boils at a different temperature. When the oil is boiled in a refinery, the different hydrocarbons boil off at different times and are collected separately. Most of the compounds that come out of the refining process are fuels, such as gasoline, diesel fuel, and jet fuel. Because these fuels are rich sources of energy and can be transported easily, they provide about 90 percent of the energy used for transportation around the world. The rest of the compounds from crude oil are used to make products such as waxes, plastics, and fertilizers.    
As in every type of mining, mining for oil has environmental consequences. Oil rigs are unsightly and spills are all too common. Oil spills can be disastrous to ecosystems.