The alkanes topic in A-Level Chemistry typically introduces students to the structure, properties, reactions, industrial uses, and environmental effects of saturated hydrocarbons.
Students are expected to know that alkanes are saturated hydrocarbons
containing only single C–C and C–H bonds. Some specifications also
require the general formula of alkanes.
A major part of the topic is understanding that alkanes are major components of crude oil. Students learn how crude oil is separated by fractional distillation, and how long-chain alkanes are broken down by cracking into shorter, more useful alkanes and alkenes.
C–C bonds in larger molecules.Alkanes are studied as fuels, so the syllabus commonly includes complete and incomplete combustion.
Students are often expected to understand the environmental consequences of burning alkane fuels, including air pollution and harmful emissions. The role of catalytic converters in reducing some pollutants is also part of several specifications.
A key organic reaction for alkanes is their reaction with halogens, such as chlorine or bromine, under ultraviolet light. This is taught as free-radical substitution.
Students may be expected to write or explain the mechanism using these stages.
Some specifications also require students to explain why alkanes are relatively unreactive, especially toward polar reagents. This is linked to the strength and low polarity of their bonds.
Depending on the exam board, students may study trends in boiling point with increasing chain length, as well as the effect of branching on boiling temperature.