Where crude oil comes from, what a hydrocarbon is, the first four alkanes and their formulae, and how the fractions are separated and what each is used for.
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1.What is crude oil?
A finite resource found in rocks, made from the remains of ancient biomass, mainly plankton, buried in mud millions of years ago.
2.What kind of mixture is crude oil?
A mixture of a very large number of compounds, most of which are hydrocarbons.
3.What is a hydrocarbon?
A compound made from hydrogen and carbon atoms only.
4.What is an alkane?
A saturated hydrocarbon, in which every carbon to carbon bond is a single bond.
5.What does saturated mean?
The molecule contains as many hydrogen atoms as possible, because there are no double bonds.
6.State the general formula for alkanes.
CnH2n+2
7.Name and give the formula of the first alkane.
Methane, CH4.
8.Name and give the formula of the second alkane.
Ethane, C2H6.
9.Name and give the formula of the third alkane.
Propane, C3H8.
10.Name and give the formula of the fourth alkane.
Butane, C4H10.
11.An alkane has 6 carbon atoms. How many hydrogens?
(2 x 6) + 2 = 14, so C6H14.
12.What is a homologous series?
A family of compounds with the same general formula and similar chemical properties, whose physical properties change gradually along the series.
13.What is fractional distillation used for?
Separating crude oil into fractions, each containing molecules with a similar number of carbon atoms.
14.Describe how fractional distillation of crude oil works.
The oil is heated until most of it vaporises and enters a tall column that is hot at the bottom and cooler at the top. Each fraction condenses and is collected at the level matching its boiling point.
15.Where do the fractions with the shortest chains come off?
Near the top of the column, because they have the lowest boiling points.
16.Where do the fractions with the longest chains come off?
Near the bottom, because they have the highest boiling points.
17.Name five useful fractions from crude oil.
Petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases.
18.What is bitumen used for?
Surfacing roads and roofs.
19.What is kerosene mainly used for?
Aircraft fuel.
20.Why is crude oil described as finite?
It formed over millions of years and is being used far faster than it can be replaced, so supplies will eventually run out.
21.What is a feedstock?
A raw material used to make other useful chemicals.
22.What is the petrochemical industry?
The industry that uses fractions from crude oil to make products such as solvents, lubricants, polymers and detergents.
23.Why is crude oil so important beyond fuel?
It is the source of the vast majority of everyday organic compounds, from plastics to medicines.
24.Why can crude oil be separated by physical means?
It is a mixture, not a compound, so the substances in it are not chemically bonded together.
25.What holds alkane molecules to one another?
Weak intermolecular forces, not the strong covalent bonds inside each molecule.
26.Why do longer alkanes have higher boiling points?
Larger molecules have stronger intermolecular forces between them, so more energy is needed to separate them.
27.Draw the displayed formula of methane in words.
A central carbon atom with four single bonds, one to each of four hydrogen atoms.
28.Why is methane a gas at room temperature?
It is a very small molecule with very weak intermolecular forces, so very little energy separates the molecules.
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