Alkanes, Cycloalkanes, Alkenes and Addition Reactions
Name and draw hydrocarbons within the specified carbon range, use general formulae and represent addition reactions of alkenes.
How to study National 5 Chemistry
Move between particle explanations, formulae, calculations, experimental evidence and justified conclusions, while using official materials for exact written-paper and assignment practice.
Core concepts
Concept 1
Alkanes are saturated hydrocarbons with general formula CₙH₂ₙ₊₂; cycloalkanes are saturated cyclic hydrocarbons with general formula CₙH₂ₙ.
Exam cue: Distinguish an alkene from a cycloalkane by structure, not by molecular formula alone.
Concept 2
Alkenes are unsaturated hydrocarbons containing a C=C functional group and have general formula CₙH₂ₙ.
Exam cue: Number a carbon chain so the double bond or substituent receives the appropriate position.
Concept 3
Alkenes undergo addition with hydrogen, halogens or water to form alkanes, dihaloalkanes or alcohols.
Exam cue: Open the C=C bond and account for every atom when drawing an addition product.
Risk pitfalls and guardrails
Using CₙH₂ₙ as proof that a molecule must be an alkene.
Guardrail: Check formulae, charges, units, state or experimental conditions before committing to the final conclusion.
Losing a carbon or hydrogen when moving between name, molecular formula and structure.
Guardrail: Check formulae, charges, units, state or experimental conditions before committing to the final conclusion.
Treating an addition reaction as if a small molecule must be eliminated.
Guardrail: Check formulae, charges, units, state or experimental conditions before committing to the final conclusion.
Memory anchors
Alkane formula
Alkanes are saturated hydrocarbons with general formula CₙH₂ₙ₊₂.
Cycloalkane formula
Unbranched cycloalkanes are saturated rings with general formula CₙH₂ₙ.
Alkene formula
Alkenes contain a C=C bond and have general formula CₙH₂ₙ.
Hydrogenation
Adding hydrogen across C=C forms an alkane.
Halogen addition
Adding a halogen across C=C forms a dihaloalkane.
Hydration
Adding water across C=C forms an alcohol.
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 the general formula of an alkane?
What is the molecular formula of hexane?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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