Small Molecules and Polymers

This lesson covers the properties of small molecules (simple molecular substances) and introduces polymers, as required by the AQA GCSE Chemistry specification (4.2.2). You need to understand why small molecules have low melting and boiling points, why they do not conduct electricity, and how polymers differ in their properties due to their giant molecular structure.

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Simple Molecular Substances

Simple molecular substances are made up of small molecules containing a fixed number of atoms held together by strong covalent bonds. However, between the molecules there are only weak intermolecular forces (forces of attraction between molecules). It is these intermolecular forces — not the covalent bonds — that determine the physical properties of the substance.

Key Distinction: Bonds vs Forces

	Covalent Bonds	Intermolecular Forces
Location	Within the molecule (between atoms)	Between molecules
Strength	Strong	Weak
What happens when substance melts/boils?	Bonds do NOT break	Forces ARE overcome
Energy required	Large	Small