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Polymers and ethanol from oil


The products of cracking include alkenes (for example ethene and propene). The alkenes are a family of hydrocarbons that share the same general formula. This is CnH2n.

The general formula means that the number of hydrogen atoms in an alkene is double the number of carbon atoms. For example, ethene is C2H4 and propene is C3H6. Alkene molecules can be represented by displayed formulae, in which each atom is shown as its symbol (C or H) and the chemical bonds between them by a straight line.

Structure of alkenes

alkeneformulachemical structureball-and-stick model
etheneC2H4ethene has 2 carbon atoms and 4 hydrogen atomsthe carbon atoms are joined by a double bond
propeneC3H6propene has 3 carbon atoms and 6 hydrogen atomstwo of the carbon atoms are joined by a double bond

Alkenes are unsaturated hydrocarbons. They contain a double bond, which is shown as two lines between two of the carbon atoms. The presence of this double bond allows alkenes to react in ways that alkanes cannot. They can react with oxygen in the air, so they could be used as fuels. But they are more useful than that. They can be used to make ethanol - alcohol - and polymers - plastics - two crucial products in today's world.

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