Properties of Simple Molecular Substances

This lesson covers the properties of simple molecular substances as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand why substances like water, oxygen and methane have low melting and boiling points and why they do not conduct electricity. The key is the distinction between strong covalent bonds within molecules and weak forces between molecules.

---

What Are Simple Molecular Substances?

A simple molecular substance (also called a simple molecule) is made up of a small number of atoms held together by strong covalent bonds.

Examples include:

Substance	Formula	Atoms per Molecule
Hydrogen	H₂	2
Water	H₂O	3
Oxygen	O₂	2
Carbon dioxide	CO₂	3
Methane	CH₄	5
Ammonia	NH₃	4

---

Two Types of Force in Simple Molecular Substances

To explain the properties, you must distinguish between two types of force: