This deep dive covers Understanding Intermolecular Forces 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 3 of 11 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
🔬 Understanding Intermolecular Forces
The Two Types of Forces:
• Strong bonds between atoms sharing electrons
• Hold atoms together INSIDE the molecule
• NOT broken when melting or boiling
• The molecule stays intact as a gas
• Weak attractions between DIFFERENT molecules
• Hold molecules close to each other in solid/liquid
• ARE broken when melting or boiling
• Very little energy needed to overcome them
Common Simple Molecular Substances:
• Boiling point: 100°C
• Relatively high for a simple molecule
• Has stronger intermolecular forces (hydrogen bonding)
• Still much lower than ionic compounds!
• Sublimes at -78°C (goes straight from solid to gas)
• Very weak intermolecular forces
• Molecules spread apart easily
• O₂ boils at -183°C, N₂ at -196°C
• Tiny molecules with very weak intermolecular forces
• Almost no attraction between molecules
• Higher melting points than small molecules
• More atoms = more surface area = more intermolecular forces
• Still lower than ionic/giant covalent compounds
Key Exam Point: When explaining low melting/boiling points, ALWAYS say "weak intermolecular forces" NOT "weak covalent bonds" — the covalent bonds are strong! It's the forces BETWEEN molecules that are weak.
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.