Oil
Oil, in a general sense, is a chemical compound that is not miscible with
water, and is in a
liquid state at ambient temperatures. Such substances are sometimes described as hydrophobic or lipophilic .
Emulsifiers allow oils and water to mix.
Encyclopedia
Oil, in a general sense, is a chemical compound that is not miscible with
water, and is in a
liquid state at ambient temperatures. Such substances are sometimes described as hydrophobic or lipophilic .
Emulsifiers allow oils and water to mix.
Types
Hydrocarbons
Certain oils are liquid
hydrocarbons or mixtures thereof. They differ from other organic compounds, such as
alcohols,
ketones and
ethers in that they are non-
polar. Waxes are chemically similar to this kind of oil, differing only in that they have longer hydrocarbon chains, resulting in a greater number of intermolecular attractions per molecule, and are thus solids at room temperature.
Triglycerides
The word oil also refers to
triglycerides which are liquids at room temperature, usually in the context of cooking oil. The triglycerides in cooking oil tend to contain unsaturated
fatty acid chains, hence the terms
monounsaturate and
polyunsaturate. Triglycerides found in animals are generally
saturated and so tend to be solids at room temperature - if solid, they are called animal fats.
Animal triglycerides are mostly solid while vegetable triglycerides are mostly liquid because animal triglycerides are more saturated. The unsaturation in vegetable triglycerides is in the form of
cis alkene groups, which form a kink in the fatty acid chain, preventing neighbouring fatty acid chains from aligning. This effect limits the degree of
intermolecular attraction and so allows individual molecules to rotate with respect to each other, the condition for a
liquid.
Examples
Biological
- Vegetable oil, non-volatile oils extracted from plants, usually the seeds
- Essential oil, volatile aromatic oils extracted from plants
- Animal fat, obtained from animal sources
Mineral
- Petroleum or crude oil, a natural resource found in liquid state in the Earth's crust.
- Mineral oil, a by-product of the distillation of petroleum
- Oil shale, a group of sedimentary rocks which may be distilled to obtain petroleum
- Coal oil, distilled from bituminous shale or mineral wax
Synthetic
- Synthetic oil, manufactured from smaller molecules using chemical processes
Applications
;Cooking oil
Edible vegetable and animal oils are frequently used in cooking, due to their ability to reach higher temperatures than water. They also serve as a flavour enhancer and as a supporting medium for
vitamins and
aromas.
Grey oil
Grey oil is the disused part of crude oil and is disposed off by being put in the bin.
Fuel oil
Oils contain a large amount of stored energy, which can be converted by burning into other forms of energy. Fuel oil is used for heating, lighting and powering combustion engines. Oils used for this purpose are usually derived from petroleum, but biological sources of energy are being evaluated as an alternative to the increasingly expensive crude oil.
Lubrication
Due to their non-polarity, oils do not easily adhere to other substances. This makes them useful as lubricants for various engineering purposes. Suitable oils are often found in the mineral spectrum, as biological oils degrade quickly in most environmental conditions.
Petrochemistry
Petrochemistry is the process of refining crude oil into useful raw materials,
plastics, and other oils.
Heat transportMany oils have higher boiling points than water and lower electrical conductivity, allowing them to be used for liquid cooling systems, especially where electricity is used.
PaintingColor pigments can be easily dissolved in oil, making oil 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.
