1.8- understand how to classify a substance as an element, a compound or a mixture

Element – are substances that are made up of only one type of atom, and cannot be split into anything simpler by chemical means (elements such as oxygen are described as diatomic, contain two atoms)

Compound- a substance in which two or more elements chemically combine in fixed proportions        

Mixture -Various substances mixed together that are not chemically combined to one another, can be in any proportion. 

In a mixture each element keeps its own properties, whereas in a compound they might react differently together. Mixtures can be separated by physical means, e.g. iron and sulphur mixture with a magnet.

However, the elements in a compound cannot be separated physically, and that must be done with chemical reactions.