Pure substances and mixtures
Pure substances and mixtures
In chemistry, a pure substance contains only one element or one compound. It has a fixed composition throughout. A mixture contains two or more substances that are not chemically bonded, so its composition can vary.
Step-by-step lessons on Edexcel GCSE Chemistry 3.2 Methods of separating and purifying substances, covering 3.2.1 Pure substances and mixtures, 3.2.2 Techniques for separating mixtures, 3.2.3 Paper chromatography and Rf values, and 3.2.4 Making water potable. Each one builds up to exam-style questions. Nail the core quantitative topics — moles, balancing equations and calculations — early on, since they underpin higher-tier questions across every paper and topic.