This topic summary covers Knowledge Organiser: Simple Molecules 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 11 of 11 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Simple Molecules
Key Terms
- Simple molecular: small molecules with covalent bonds within and weak forces between
- Intermolecular forces: weak attractions BETWEEN molecules
- Intramolecular bonds: strong covalent bonds WITHIN molecules
Must-Know Facts
- Low MP/BP — weak intermolecular forces break (not covalent bonds)
- Do NOT conduct — no ions or free electrons
- Often gases or liquids at room temperature
- Larger molecule = more intermolecular forces = higher MP
- Examples: H₂O, CO₂, O₂, N₂, CH₄, NH₃, Cl₂
Key Equations
- No calculation equations — descriptive topic
- Boiling point comparison: larger molecule → more intermolecular forces → higher BP
- No conduction: no free ions or free electrons in simple molecular compounds
Common Mistakes
- Saying covalent bonds break when simple molecules melt: It is the INTERMOLECULAR FORCES between molecules that break — the covalent bonds within molecules stay intact
- Saying simple molecular substances conduct electricity: They have no free ions or free electrons — no electrical conduction is possible
- Thinking all covalent substances have low melting points: Only simple molecular ones do — giant covalent structures (diamond, graphite) have very high melting points
- Ignoring molecule size when comparing boiling points: Larger molecules have more electrons → stronger intermolecular forces → higher boiling point
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.
Quick recall flashcards
What are intermolecular forces?
Weak forces of attraction between different molecules
What does molecular formula show?
Number and type of atoms in one molecule (e.g., H₂O, CO₂, CH₄)