## Oil

### Gap-fill exercise
Study material: Maritime Transportation, Chemistry and Oil_oer.pdf
Test generated using the freeware software provided by Hot Potatoes (version 6). http://hotpot.uvic.ca/

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!
Each petroleum variety has a unique composition, which define its physical and chemical properties. Crude oil is mainly a complex mixture of a very large number of different , i.e., substances mainly composed by hydrogen and carbon, their simplest chemical composition denoted by CnHm; therefore they are organic compounds as is the main element in their molecular structure. Organic compounds containing nitrogen, oxygen, sulphur, and trace amounts of (vanadium, nickel, copper, iron,…) are also present in petroleum; collectively these atoms, other than C & H, are called .
Separation of the petroleum compounds is based on its different ; whose with lower boiling point leave the from (e.g. liquefied petroleum gas ––, gasoline, naphtha), whereas those having higher boiling point leave it at the (e.g. fuel oil, lubricating oils, wax and tar), and in the middle distillates compounds like kerosene and diesel.
Specific gravity and American Petroleum Institute () gravity are density-related properties of oils often used. The API gravity scale arbitrarily assigns an API gravity of to pure water.
Density dependence on has capital relevance when huge amounts of crude oil and/or petroleum products, any liquid in general, so are used for converting volumes at an observed temperature and gravity or density to a standard temperature (60 ºF or 15 ºC).
Each petroleum variety has a unique composition, which define its physical and chemical properties. Hydrocarbons (CnHm) in crude oils can be grouped in:
,
and
. Depending on the carbon atoms arrangement in the carbon backbone, can be classified as and ; paraffins also divide in linear, where carbon atoms are joined in a snake-like structure, o branched. Linear, also named , and branched alkanes with the same number of carbon atoms are , i.e., molecules having the same the molecular formula. At room temperature and pressure, n-alkanes up to four carbons atoms are , from five to 16 , and those with more carbon atoms.37 Branched-chain alkanes have boiling points than their straight-chain counterparts, and the contrary applies to naphthenes. are composed by n-alkanes (the predominant species and crude specific), iso-alkanes, alkyl cyclic compounds and alkyl aromatics. It is generally accepted that n-alkanes from C18 to C40 represent waxy material.
are compounds that have at least one benzene ring as part of their chemical structure. They include mono-, di-, and polynuclear aromatic hydrocarbons () with and without alkyl side chains.
Benzene, toluene, ethyl benzene, and xylenes (collectively known as ) are hazardous carcinogenic and neurotoxic compounds usually classified as priority pollutants. contain two or more fused benzene rings, and are also compounds of environmental concern.
consist mainly of carbon and hydrogen (C:H ratio is approximately 1:1.2), and nitrogen, oxygen, sulphur, and trace amounts of vanadium and nickel are also present
In the oil market the amount of sulphur present in crude oil determines its price, crude is that of with sulphur content less than 0.5%, and above of that limit crude oil is classified as .
The International Maritime Organization defines oil (those belonging to ) as a petroleum based oil that consists of hydrocarbon fractions: (i) at least 50% of which by volume, distil at a temperature of 340°C (645°F); and (ii) at least 95% of which by volume, distil at a temperature of 370°C (700°F). and oil all oils which are not within the previous category.
The fate of spilled oil in water bodies, also known as , is governed by physical, chemical, and biological processes that depend on the oil properties, hydrodynamics, meteorological and environmental conditions.