Pure Substances and Mixtures

This lesson covers the distinction between pure substances and mixtures, how to use melting point to determine purity, and the concept of formulations, as required by the Edexcel GCSE Chemistry specification (1CH0, Topic 1). Understanding what "pure" means in chemistry — which is different from everyday language — is essential for chemical analysis and separation techniques.

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Pure Substances in Chemistry

In chemistry, a pure substance contains only one type of element or one type of compound. This is very different from the everyday meaning of "pure."

Term	Everyday Meaning	Chemistry Meaning
Pure	Clean, natural, uncontaminated	Contains only one element or compound
Pure water	Clean drinking water	Contains only H\u2082O molecules (nothing else)
Pure orange juice	Juice with no additives	Would mean only one chemical compound (not realistic)
Pure gold	High-quality gold	Contains only gold atoms (24 carat)

Examples of Pure Substances