2.5 Organic Chemistry
Homologous series, hydrocarbons, crude oil and fractions, cracking, alkanes, alkenes, alcohols, carboxylic acids and polymers.
How to study for CCEA GCSE Chemistry
Connect particle models to observations, balance every quantitative relationship, and prepare each prescribed practical from safe method through analysis and evaluation.
Core concepts
Concept 1
A homologous series has a common general formula and functional group, similar chemistry and gradual physical-property changes.
Exam cue: Use the general formula and functional group to classify or complete a structure.
Concept 2
Fractional distillation separates crude oil by boiling range, while cracking converts less useful long molecules into smaller alkanes and alkenes.
Exam cue: Relate chain length to boiling point, viscosity, volatility and fuel use.
Concept 3
Functional groups determine reactions of alkenes, alcohols and carboxylic acids, including polymer and ester formation.
Exam cue: Distinguish addition polymerisation from small-molecule addition or combustion.
Risk pitfalls and guardrails
Calling crude oil a single hydrocarbon.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a particle-level explanation with a vague observation.
Using the alkane formula for an alkene.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a particle-level explanation with a vague observation.
Drawing a polymer repeat unit without opening the carbon-carbon double bond.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a particle-level explanation with a vague observation.
Memory anchors
Homologous series
Organic family sharing a general formula, functional group and similar reactions.
Hydrocarbon
A compound containing carbon and hydrogen only.
Alkane
A saturated hydrocarbon with general formula CnH2n+2.
Alkene
An unsaturated hydrocarbon with a carbon-carbon double bond and formula CnH2n.
Cracking
Thermal decomposition of long hydrocarbons into shorter alkanes and alkenes.
Addition polymerisation
Many alkene monomers join after their double bonds open.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is a hydrocarbon?
What is the general formula of alkanes?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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