Bonds DON'T break, forces DO: When a simple molecular substance melts, the intermolecular FORCES between molecules break. The covalent BONDS inside molecules do NOT break. Remember this by contrast: salt melting breaks the ionic lattice; ice melting breaks the intermolecular forces between H₂O molecules.
Size → Strength → State:
- Larger molecule → more intermolecular forces → higher melting point
- O₂ (tiny) = gas at room temp; wax (large) = solid at room temp
State at room temperature memory trick:
- O₂, N₂, CO₂, CH₄, NH₃, HCl → all gases (tiny molecules, very weak forces)
- H₂O, Br₂, Hg → liquids (slightly stronger forces)
- I₂, wax → solids (larger molecules, stronger forces)
This memory aid covers Memory Aids within Simple Molecules for GCSE Chemistry. Revise Simple Molecules in Bonding & Structure for GCSE Chemistry with 20 exam-style questions and 21 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 8 of 11 in this topic. Use it for quick recall, then test yourself straight afterwards so the memory aid becomes usable in an answer.
Practice questions for Simple Molecules
Which type of force holds simple molecules together as a substance?
Explain why chlorine (Cl2) has a low boiling point.