This deep dive covers Deep Dive: Understanding Alkanes within Alkanes for GCSE Chemistry. Topic 38: Alkanes It is section 3 of 12 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
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Section 3 of 12
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20 questions
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🔬 Deep Dive: Understanding Alkanes
The General Formula: CₙH₂ₙ₊₂
- n = number of carbon atoms
- Plug in n to find the formula for any alkane
- Example: n=3 → C₃H₂₍₃₎₊₂ = C₃H₈ (propane)
Why "Saturated"?
- Alkanes have ONLY single bonds between carbons
- This means every carbon is bonded to as many hydrogens as possible
- The molecule is "saturated" with hydrogen — can't hold any more!
- Compare to alkenes which have C=C double bonds (unsaturated)
The First Four Alkanes (MUST memorise!):
| Name | Formula | Carbons | State at room temp |
|---|---|---|---|
| Methane | CH₄ | 1 | Gas |
| Ethane | C₂H₆ | 2 | Gas |
| Propane | C₃H₈ | 3 | Gas |
| Butane | C₄H₁₀ | 4 | Gas |
Naming Pattern: Meth (1), Eth (2), Prop (3), But (4), Pent (5), Hex (6)... + "ane"
Properties of Alkanes:
- Longer chains = higher boiling point (more intermolecular forces)
- First four are gases, then liquids, then waxy solids
- Don't mix with water (immiscible)
- Burn well in oxygen (good fuels!)
- Generally unreactive — only combustion and reactions with halogens