An oil is any nonpolar chemical substance
that is a viscous liquid
at ambient temperatures and is both hydrophobic
(does not mix with water
, literally "water fearing") and lipophilic
(mixes with other oils, literally "fat loving"). Oils have a high carbon and hydrogen content and are usually flammable and surface active
. Most oils are unsaturated lipids
that are liquid at room temperature.
The general definition of oil includes classes of chemical compounds that may be otherwise unrelated in structure, properties, and uses. Oils may be animal
, or petrochemical
in origin, and may be volatile
or non-volatile. They are used for food (e.g., olive oil
), fuel (e.g., heating oil
), medical purposes (e.g., mineral oil
(e.g. motor oil
), and the manufacture of many types of paints, plastics, and other materials. Specially prepared oils are used in some religious ceremonies and rituals as purifying agents.
First attested in English 1176, the word ''oil'' comes from Old French
''oile'', from Latin
''oleum'', which in turn comes from the Greek
(''elaion''), "olive oil, oil" and that from (''elaia''), "olive
tree", "olive fruit". The earliest attested forms of the word are the Mycenaean Greek
, ''e-ra-wo'' and , ''e-rai-wo'', written in the Linear B
Organic oils are produced in remarkable diversity by plants, animals, and other organisms through natural metabolic
'' is the scientific term for the fatty acid
s and similar chemicals often found in the oils produced by living things, while oil refers to an overall mixture of chemicals. Organic oils may also contain chemicals other than lipids, including protein
es (class of compounds with oil-like properties that are solid at common temperatures) and alkaloid
Lipids can be classified by the way that they are made by an organism, their chemical structure and their limited solubility
in water compared to oils. They have a high carbon
content and are considerably lacking in oxygen
compared to other organic compounds and minerals; they tend to be relatively nonpolar
molecules, but may include both polar and nonpolar regions as in the case of phospholipid
s and steroids.
[Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter. ''Molecular Biology of the Cell''. New York: Garland Science, 2002, pp. 62, 118-119.]
Crude oil, or petroleum
, and its refined components, collectively termed ''petrochemicals
'', are crucial resources in the modern economy. Crude oil originates from ancient fossilized organic material
s, such as zooplankton
, which geochemical
processes convert into oil. The name "mineral oil" is a misnomer
, in that minerals are not the source of the oil—ancient plants and animals are. Mineral oil is organic. However, it is classified as "mineral oil" instead of as "organic oil" because its organic origin is remote (and was unknown at the time of its discovery), and because it is obtained in the vicinity of rocks, underground traps, and sands. ''Mineral oil
'' also refers to several specific distillates of crude oil.
Several edible vegetable and animal oils, and also fat
s, are used for various purposes in cooking and food preparation. In particular, many foods are fried in oil much hotter than boiling water. Oils are also used for flavoring and for modifying the texture of foods (e.g. Stir Fry
). Cooking oils are derived either from animal fat, as butter
and other types, or plant oils from the olive
and many other species.
Oils are applied to hair to give it a lustrous look, to prevent tangles and roughness and to stabilize the hair to promote growth. See hair conditioner
Oil has been used throughout history as a religious medium. It is often considered a spiritually purifying agent and is used for anointing
purposes. As a particular example, holy anointing oil
has been an important ritual liquid for Judaism
are easily suspended
in oil, making it suitable as a supporting medium for paints
. The oldest known extant oil paintings date from 650 AD.
Oils are used as coolants in oil cooling
, for instance in electric transformers
. Heat transfer oils are used both as coolant
s (see oil cooling
), for heating (e.g. in oil heater
s) and in other applications of heat transfer.
Given that they are non-polar, oils do not easily adhere to other substances. This makes them useful as lubricants
for various engineering purposes. Mineral oils are more commonly used as machine lubricants than biological oils are. Whale oil
is preferred for lubricating clocks, because it does not evaporate, leaving dust, although its use was banned in the USA in 1980.
It is a long-running myth that spermaceti
from whales has still been used in NASA projects such as the Hubble Telescope
and the Voyager
probe because of its extremely low freezing temperature. Spermaceti is not actually an oil, but a mixture mostly of wax esters, and there is no evidence that NASA has used whale oil.
Some oils burn
in liquid or aerosol
form, generating light
, and heat
which can be used directly or converted into other forms of energy such as electricity or mechanical work. In order to obtain many fuel oils, crude oil
is pumped from the ground and is shipped via oil tanker
or a pipeline
to an oil refinery
. There, it is converted from crude oil to diesel fuel
(and other short-chain alkanes
), fuel oil
s (heaviest of commercial fuels, used in ships/furnaces), gasoline
(petrol), jet fuel
(historically), and liquefied petroleum gas
. A barrel of crude oil produces approximately of diesel, of jet fuel, of gasoline, of other products, split between heavy fuel oil and liquified petroleum gases,
[U.S. Energy Information Administration (EIA)]
— Retrieved 2011-10-02.
and of heating oil. The total production of a barrel of crude into various products results in an increase to .
[ Not all oils used as fuels are mineral oils, see biodiesel, vegetable oil fuel, and olive oil.
In the 18th and 19th centuries, whale oil was commonly used for lamps, which was replaced with natural gas and then electricity.
Crude oil can be refined into a wide variety of component hydrocarbons. ''Petrochemicals'' are the refined components of crude oil
and the chemical products made from them. They are used as detergents, fertilizers, medicines, paints, plastics, synthetic fibers, and synthetic rubber.
Organic oils are another important chemical feedstock, especially in green chemistry.
* Emulsifier, a chemical which allows oil and water to mix
Petroleum Online e-Learning resource from IHRDC