This deep dive covers What Makes Alkenes Special? within Alkenes for GCSE Chemistry. Revise Alkenes in Organic Chemistry for GCSE Chemistry with 20 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 3 of 14 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 3 of 14
Practice
20 questions
Recall
15 flashcards
🔬 What Makes Alkenes Special?
General Formula: CₙH₂ₙ
- Compare to alkanes: CₙH₂ₙ₊₂ — alkenes have 2 fewer hydrogens
- This is because of the C=C double bond
- Example: Ethene = C₂H₄ (not C₂H₆ like ethane)
Unsaturated = Not Full of Hydrogen
- The double bond can "open up" and add more atoms
- The molecule isn't saturated with hydrogen — it could hold more!
- This makes alkenes much more reactive than alkanes
The First Four Alkenes (MUST memorise!):
1. Ethene (C₂H₄) — used to make poly(ethene) (plastic bags)
2. Propene (C₃H₆) — used to make poly(propene) (food containers)
3. Butene (C₄H₈) — can exist as different isomers
4. Pentene (C₅H₁₀) — multiple isomer positions possible