Pure & Impure
- In everyday language we use the word pure to describe when something is natural or clean and to which nothing else has been added
- In chemistry a pure substance may consist of a single element or compound which contains no other substances
- For example a beaker of a sample of pure water contains only H2O molecules and nothing else
- If salt were added to the beaker then a mixture is produced
- A mixture consists of two or more elements or compounds that are physically mixed together, they are not chemically combined
- The chemical properties of the substances in a mixture remain unchanged
- Substances in mixtures can be separated by physical means
- Air for example is a mixture of nitrogen, oxygen and some other gases such as carbon dioxide and argon
Diagram showing how to represent elements, compounds and mixtures using particle diagrams