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A bottle of olive oil used in food Italian olive oil 2007.jpg
A bottle of olive oil used in food

An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) and lipophilic (mixes with other oils). Oils 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, vegetable, or petrochemical in origin, and may be volatile or non-volatile. [1] They are used for food (e.g., olive oil), fuel (e.g., heating oil), medical purposes (e.g., mineral oil), lubrication (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, [2] which in turn comes from the Greek ἔλαιον (elaion), "olive oil, oil" [3] and that from ἐλαία (elaia), "olive tree", "olive fruit". [4] [5] The earliest attested forms of the word are the Mycenaean Greek 𐀁𐀨𐀺, e-ra-wo and 𐀁𐁉𐀺, e-rai-wo, written in the Linear B syllabic script. [6]


Organic oils

Organic oils are produced in remarkable diversity by plants, animals, and other organisms through natural metabolic processes. Lipid is the scientific term for the fatty acids, steroids 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 proteins, waxes (class of compounds with oil-like properties that are solid at common temperatures) and alkaloids.

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 and hydrogen 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 phospholipids and steroids. [7]

Mineral oils

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 materials, such as zooplankton and algae, which geochemical processes convert into oil. [8] 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.[ citation needed ]



Several edible vegetable and animal oils, and also fats, 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, lard and other types, or plant oils from olive, maize, sunflower and many other species. [9]


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.[ citation needed ]


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 [10] and Christianity. [11]


Oils have been consumed since ancient times. Oils hold lots of fats and medical properties. A good example is olive oil. Olive oil holds a lot of fats within it which is why it was also used in lighting in ancient Greece and Rome. So people would use it to bulk out food so they would have more energy to burn through the day. Olive oil was also used to clean the body in this time as it would trap the moisture in the skin while pulling the grime to the surface. It was used as an ancient form of unsophisticated soap. It was applied on the skin then scrubbed off with a wooden stick pulling off the excess grime and creating a layer where new grime could form but be easily washed off in the water as oil is hydrophobic. [12] Fish oils hold the omega-3 fatty acid. This fatty acid helps with inflammation and reduces fat in the bloodstream.[ citation needed ]  


Color pigments are easily suspended in oil, making it suitable as a supporting medium for paints. The oldest known extant oil paintings date from 650 AD. [13]

Heat transfer

Oils are used as coolants in oil cooling, for instance in electric transformers. Heat transfer oils are used both as coolants (see oil cooling), for heating (e.g. in oil heaters) and in other applications of heat transfer.[ citation needed ]


Synthetic motor oil Motor oil.jpg
Synthetic motor oil

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 US in 1980. [14]

It is a long-running myth that spermaceti from whales has still been used in NASA projects such as the Hubble Space 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. [15]


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 (petrodiesel), ethane (and other short-chain alkanes), fuel oils (heaviest of commercial fuels, used in ships/furnaces), gasoline (petrol), jet fuel, kerosene, benzene (historically), and liquefied petroleum gas. A 42-US-gallon (35 imp gal; 160 L) barrel of crude oil produces approximately 10 US gallons (8.3 imp gal; 38 L) of diesel, 4 US gallons (3.3 imp gal; 15 L) of jet fuel, 19 US gallons (16 imp gal; 72 L) of gasoline, 7 US gallons (5.8 imp gal; 26 L) of other products, 3 US gallons (2.5 imp gal; 11 L) split between heavy fuel oil and liquified petroleum gases, [16] and 2 US gallons (1.7 imp gal; 7.6 L) of heating oil. The total production of a barrel of crude into various products results in an increase to 45 US gallons (37 imp gal; 170 L). [16]

In the 18th and 19th centuries, whale oil was commonly used for lamps, which was replaced with natural gas and then electricity. [17]

Chemical feedstock

Crude oil can be refined into a wide variety of component hydrocarbons. Petrochemicals are the refined components of crude oil [18] 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.

See also

Related Research Articles

A lubricant is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces. The property of reducing friction is known as lubricity.

<span class="mw-page-title-main">Petroleum</span> Naturally occurring flammable liquid

Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name petroleum covers both naturally occurring unprocessed crude oil and petroleum products that consist of refined crude oil.

<span class="mw-page-title-main">Diesel fuel</span> Liquid fuel used in diesel engines

Diesel fuel, also called diesel oil or historically heavy oil, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and then injection of fuel. Therefore, diesel fuel needs good compression ignition characteristics.

Naphtha is a flammable liquid hydrocarbon mixture. Generally, it is a fraction of crude oil, but it can also be produced from natural gas condensates, petroleum distillates, and the fractional distillation of coal tar and peat. In some industries and regions, the name naphtha refers to crude oil or refined petroleum products such as kerosene or diesel fuel.

<span class="mw-page-title-main">Vegetable oil</span> Oil extracted from seeds or from other parts of fruits

Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are mixtures of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fats from seeds. Olive oil, palm oil, and rice bran oil are examples of fats from other parts of fruits. In common usage, vegetable oil may refer exclusively to vegetable fats which are liquid at room temperature. Vegetable oils are usually edible.

<span class="mw-page-title-main">Synthetic oil</span> Lubricant consisting of artificially made chemical compounds

Synthetic oil is a lubricant consisting of chemical compounds that are artificially modified or synthesised. Synthetic lubricants can be manufactured using chemically modified petroleum components rather than whole crude oil, but can also be synthesized from other raw materials. The base material, however, is still overwhelmingly crude oil that is distilled and then modified physically and chemically. The actual synthesis process and composition of additives is generally a commercial trade secret and will vary among producers.

<span class="mw-page-title-main">Barrel (unit)</span> Series of units for volume measurement

A barrel is one of several units of volume applied in various contexts; there are dry barrels, fluid barrels, oil barrels, and so forth. For historical reasons the volumes of some barrel units are roughly double the volumes of others; volumes in common use range approximately from 100 to 200 litres. In many connections the term drum is used almost interchangeably with barrel.

<span class="mw-page-title-main">Barrel</span> Hollow cylindrical container

A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, usually alcoholic beverages; a small barrel or cask is known as a keg.

<span class="mw-page-title-main">Saponification value</span> Milligrams of a base required to saponify 1g of fat

Saponification value or saponification number represents the number of milligrams of potassium hydroxide (KOH) or sodium hydroxide (NaOH) required to saponify one gram of fat under the conditions specified. It is a measure of the average molecular weight of all the fatty acids present in the sample in form of triglycerides. The higher the saponification value, the lower the fatty acids average length, the lighter the mean molecular weight of triglycerides and vice versa. Practically, fats or oils with high saponification value are more suitable for soap making.

<span class="mw-page-title-main">Tank car</span> Train car for holding liquids and gases

A tank car is a type of railroad car or rolling stock designed to transport liquid and gaseous commodities.

<span class="mw-page-title-main">Petroleum product</span> Products ultimately derived from crude oil

Petroleum products are materials derived from crude oil (petroleum) as it is processed in oil refineries. Unlike petrochemicals, which are a collection of well-defined usually pure organic compounds, petroleum products are complex mixtures. Most petroleum is converted into petroleum products, which include several classes of fuels.

<span class="mw-page-title-main">Industrial wastewater treatment</span> Processes used for treating wastewater that is produced by industries as an undesirable by-product

Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater may be reused or released to a sanitary sewer or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants. Most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans. This applies to industries that generate wastewater with high concentrations of organic matter, toxic pollutants or nutrients such as ammonia. Some industries install a pre-treatment system to remove some pollutants, and then discharge the partially treated wastewater to the municipal sewer system.

Shale oil is an unconventional oil produced from oil shale rock fragments by pyrolysis, hydrogenation, or thermal dissolution. These processes convert the organic matter within the rock (kerogen) into synthetic oil and gas. The resulting oil can be used immediately as a fuel or upgraded to meet refinery feedstock specifications by adding hydrogen and removing impurities such as sulfur and nitrogen. The refined products can be used for the same purposes as those derived from crude oil.

In chemistry, acid value is a number used to quantify the acidity of a given chemical substance. It is the quantity of base, expressed as milligrams of KOH required to neutralize the acidic constituents in 1 gram of a sample.

Whale oil is oil obtained from the blubber of whales. Oil from the bowhead whale was sometimes known as train-oil, which comes from the Dutch word traan.

<span class="mw-page-title-main">Tank truck</span> Motor vehicle designed to carry liquefied loads, dry bulk cargo or gases on roads

A tank truck, gas truck, fuel truck, or tanker truck or tanker is a motor vehicle designed to carry liquids or gases on roads. The largest such vehicles are similar to railroad tank cars, which are also designed to carry liquid loads. Many variants exist due to the wide variety of liquids that can be transported. Tank trucks tend to be large; they may be insulated or non-insulated; pressurized or non-pressurized; and designed for single or multiple loads. Some are semi-trailer trucks. They are difficult to drive and highly susceptible to rollover due to their high center of gravity, and potentially the free surface effect of liquids sloshing in a partially filled tank.

Renewable Fuels are fuels produced from renewable resources. Examples include: biofuels, Hydrogen fuel, and fully synthetic fuel produced from ambient carbon dioxide and water. This is in contrast to non-renewable fuels such as natural gas, LPG (propane), petroleum and other fossil fuels and nuclear energy. Renewable fuels can include fuels that are synthesized from renewable energy sources, such as wind and solar. Renewable fuels have gained in popularity due to their sustainability, low contributions to the carbon cycle, and in some cases lower amounts of greenhouse gases. The geo-political ramifications of these fuels are also of interest, particularly to industrialized economies which desire independence from Middle Eastern oil.

Oleochemistry is the study of vegetable oils and animal oils and fats, and oleochemicals derived from these fats and oils. The resulting product can be called oleochemicals (from Latin: oleum "olive oil"). The major product of this industry is soap, approximately 8.9×106 tons of which were produced in 1990. Other major oleochemicals include fatty acids, fatty acid methyl esters, fatty alcohols and fatty amines. Glycerol is a side product of all of these processes. Intermediate chemical substances produced from these basic oleochemical substances include alcohol ethoxylates, alcohol sulfates, alcohol ether sulfates, quaternary ammonium salts, monoacylglycerols (MAG), diacylglycerols (DAG), structured triacylglycerols (TAG), sugar esters, and other oleochemical products.

Hydrotreated vegetable oil (HVO) is a biofuel made by the hydrocracking or hydrogenation of vegetable oil. Hydrocracking breaks big molecules into smaller ones using hydrogen while hydrogenation adds hydrogen to molecules. These methods can be used to create substitutes for gasoline, diesel, propane, kerosene and other chemical feedstock. Diesel fuel produced from these sources is known as green diesel or renewable diesel.

Honing oil is a liquid, solution or emulsion used to aid in the cutting or grinding of metal, typically by abrasive tools or stones, and may or may not contain oil. It can also be called machining oil,tool oil, cutting fluid, and cutting oil.


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