The general definition of oil includes classes of chemical compounds that may be otherwise unrelated in structure, properties, and uses. Oils may beanimal,vegetable, orpetrochemical in origin, and may bevolatile 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.
Etymology
First attested in English 1176, the wordoil comes fromOld Frenchoile, fromLatinoleum,[2] which in turn comes from theGreekἔλαιον (elaion), "olive oil, oil"[3] and that fromἐλαία (elaia), "olive tree", "olive fruit".[4][5] The earliest attested forms of the word are theMycenaean Greek𐀁𐀨𐀺,e-ra-wo and𐀁𐁉𐀺,e-rai-wo, written in theLinear B syllabic script.[6]
Types
Organic oils
Organic oils are produced in remarkable diversity by plants, animals, and other organisms through naturalmetabolic processes.Lipid is the scientific term for thefatty 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, includingproteins,waxes (class of compounds with oil-like properties that are solid at common temperatures) andalkaloids.
Lipids can be classified by the way that they are made by an organism, their chemical structure and their limitedsolubility in water compared to oils. They have a highcarbon andhydrogen content and are considerably lacking inoxygen compared to other organic compounds and minerals; they tend to be relativelynonpolar molecules, but may include both polar and nonpolar regions as in the case ofphospholipids and steroids.[7]
Crude oil, orpetroleum, and its refined components, collectively termedpetrochemicals, are crucial resources in the modern economy. Crude oil originates from ancientfossilizedorganic materials, such aszooplankton andalgae, whichgeochemical processes convert into oil.[8] The name "mineral oil" is amisnomer, 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 alsofats, 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, asbutter,lard and other types, or plant oils fromolive,maize,sunflower and many other species.[9]
Cosmetics
Oils are applied to hair to give it a lustrous look, to prevent tangles and roughness and to stabilize the hair to promote growth. Seehair conditioner.[citation needed]
Religion
Oil has been used throughout history as a religious medium. It is often considered a spiritually purifying agent and is used foranointing purposes. As a particular example,holy anointing oil has been an important ritual liquid forJudaism[10] andChristianity.[11]
Health
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]
Colorpigments are easilysuspended in oil, making it suitable as a supporting medium forpaints. The oldest known extant oil paintings date from 650 AD.[13]
Given that they are non-polar, oils do not easily adhere to other substances. This makes them useful aslubricants 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 thatspermaceti from whales has still been used in NASA projects such as theHubble Space Telescope and theVoyager 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 oilsburn in liquid oraerosol form, generatinglight, andheat 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 viaoil tanker or apipeline to anoil refinery. There, it is converted from crude oil todiesel fuel (petrodiesel),ethane (and other short-chainalkanes),fuel oils (heaviest of commercial fuels, used in ships/furnaces),gasoline (petrol),jet fuel,kerosene,benzene (historically), andliquefied 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]
^"The Linear B word e-ra-wo".Palaeolexicon. Word study tool of ancient languages."e-ra3-wo". Archived fromthe original on 2016-03-21. Retrieved2014-03-22.Raymoure, K.A."e-ra-wo".Minoan Linear A & Mycenaean Linear B. Deaditerranean. Archived fromthe original on 2016-03-20. Retrieved2014-03-22.
^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.
