Section 3 a) Specification

3.1 explain the terms homologous series, hydrocarbon, saturated, unsaturated, general formula and isomerism.

A homologous series is a group of compounds with the same general formula and similar chemical properties.
A hydrocarbon is a compound made up of only hydrogen and carbon particles.
Saturated means that a compound is made up of only single bonds, it has no double bonds. Alkanes are a homologous series of saturated hydrocarbons.
Unsaturated means that a compound includes double bonds. Alkenes are a homologous series of unsaturated hydrocarbons.
A general formula is a type of empirical formula that represents of all of the members of a homologous series.
Isomers are molecules with the same chemical formula but different structures (e.g. diamond and graphite are both carbon, but are very different because they are isomers)

Section 3 Specification

a) Introduction

3.1 explain the terms homologous series, hydrocarbon, saturated, unsaturated, general formula and isomerism.


b) Alkanes 

3.2 recall that alkanes have the general formula CnH2n+2

3.3 draw displayed formulae for alkanes with up to five carbon atoms in a molecule, and name the straight-chain isomers

3.4 recall the products of the complete and incomplete combustion of alkanes 3.5 describe the substitution reaction of methane with bromine to form bromomethane in the presence of UV light.


c) Alkenes 

3.6 recall that alkenes have the general formula CnH2n

3.7 draw displayed formulae for alkenes with up to four carbon atoms in a molecule, and name the straight-chain isomers (knowledge of cis- and transisomers is not required)

3.8 describe the addition reaction of alkenes with bromine, including the decolourising of bromine water as a test for alkenes.


d) Ethanol 

3.9 describe the manufacture of ethanol by passing ethene and steam over a phosphoric acid catalyst at a temperature of about 300°C and a pressure of about 60–70 atm

3.10 describe the manufacture of ethanol by the fermentation of sugars, for example glucose, at a temperature of about 30°C

3.11 evaluate the factors relevant to the choice of method used in the manufacture of ethanol, for example the relative availability of sugar cane and crude oil

3.12 describe the dehydration of ethanol to ethene, using aluminium oxide.