:''For other uses, see
Oil (disambiguation).''
An 'oil' is any
substance that is in a
viscous liquid state (''"oily"'') at ambient temperatures or slightly warmer, and is both
hydrophobic (
immiscible with
water, literally ''"water fearing"'') and
lipophilic (miscible with other oils, literally ''"fat loving"''). This general definition includes compound classes with otherwise unrelated
chemical structures,
properties, and uses, including
vegetable oils,
petrochemical oils, and volatile
essential oils. Oil is a
nonpolar substance.
Examples
Biological
★
Vegetable oils, non-volatile oils extracted from plants, usually from seeds. Vegetable oils are less stable than mineral oils, and degrade over time.
★
Essential oils, volatile aromatic oil extracted from plants.
★ Animal Oils, such as
whale oil and
cod liver oil.
Synthetic
★
Synthetic oils,
synthesised
Mineral
★ Crude oil,
petroleum, and many petroleum derivatives
fuel oils.
Applications
; Food oils
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
boiling oil, which is much hotter than boiling
water. Oils are also used for flavouring and for modifying the texture of foods e.g
Stir Fry.
Health advantages are claimed for a number of specific oils such as
omega 3 fish oils,
evening primrose oil,
flaxseed oil, etc.
Trans fats, often produced by
hydrogenating vegetable oils, are known to be harmful to health.
; Oil as
fuel
Most oils
burn in
air generating
heat which can be used directly or converted into other forms of
energy in the usual ways. Oils are used as fuels for
heating, lighting (e.g.
kerosene lamp), powering
combustion engines, and other purposes. Oils used for this purpose nowadays are usually derived from
petroleum (
fuel oil,
diesel oil,
gasoil, etc).
Renewable biological sources of energy, some of which are oils, are used as an alternative to petroleum products due to concerns about
global warming and cost.
;
Lubrication
Due to their non-polarity, oils do not easily adhere to other substances. This makes them useful as lubricants for various engineering purposes. Mineral oils are more suitable than biological oils, which degrade rapidly in most environmental conditions.
; Manufacture of petrochemicals
Crude oil can be processed into
plastics and other substances. See
Petrochemistry.
;
Heat transport
Many oils have higher
boiling points than water and are
electrical insulators, making them useful for
liquid cooling systems, especially where electricity is used.
;
Painting
Color pigments can be easily
suspended in oil, making it suitable as supporting medium for paints. The slow drying process and miscibility of oil facilitates a realistic style. This method has been used since the 15th century.
;
Religion
Oils have been used throughout history as a fragrant or religious medium. Oil is often seen as a spiritually purifying agent, for example
Chrism.
;
Massage
Oil allows massage strokes to glide along the skin. The oil is selected based on the viscosity for the type of massage being conducted. A relatively high-viscosity oil such as almond oil may be used for a luxuriant, slow style, while a lighter oil such as grape seed oil may be selected for a more athletic or rapid approach. Scent may be added.
See also
★
Emulsifier, allow oils and water to mix
★
Wax, compounds with oil-like properties that are solid at common temperature