What is Petroleum?
[[File:Petroleum cm05.jpg|thumb|Petroleum]] '''Petroleum''', (from Greek πέτρα - rock and έλαιο - oil) also called '''crude oil''', is a thick and [[black]] [[liquid]]. It is a natural material mainly made of [[hydrocarbon]]s. The hydrocarbons come from many billions of ancient [[phytoplankton]]. When they die, their bodies sink to the bottom. This formed basins of oil in many parts of the world. Most petroleum is found by drilling down through rocks on land or off-[[shore]] on the [[continental shelf]]. Major producers are in the [[Middle East]], the [[Americas]], and [[Russia]]. It is the most important world [[fuel]] source. It supplies 38% of the world's energy and is also used to make [[petrochemical]]s. Crude oil is a mixture of many different [[Organic chemistry|chemicals]] (mostly [[hydrocarbon]]s), most of which burn well. It is separated into simpler, more useful mixtures by [[fractional distillation]] in [[Oil refinery|oil refineries]] to give separate chemicals such as [[gasoline]] (or ''petrol'') for cars, [[kerosene]] for airplanes and [[tar|bitumen]] for roads. The bitumen gives crude oil its dark black color; most of the other chemicals in crude are slightly yellow or colorless. Petroleum can be easily [[transport]]ed by [[pipeline]] and [[oil tanker]]. Refined petroleum is used as [[fuel]]s; mainly [[gasoline]] (''petrol'') for cars, diesel fuel for [[diesel engine]]s used in trucks, trains and ships, [[kerosene]] fuel for jets and as [[lubricant]]s. Petrochemicals: * [[alcohol]]s * [[antiseptic]]s * [[artificial rubber]] * [[detergent]]s * [[drug]]s * [[explosive]]s * [[food additive]]s * [[insecticide]]s * [[perfume]]s * [[plastic]]s * [[textile]] fiber == Problems == Petroleum resource is limited and [[non-renewable]]. Some believe it will run out within 70 years after a [[peak oil]] early in the 21st century. Burning petroleum or other [[fossil fuel]] adds the [[carbon]] in the oil to the [[oxygen]] in the air to create [[carbon dioxide]], which is an [[Air pollution|air pollutant]].