Learn about elements, compounds and mixtures in this KS3 Chemistry guide from BBC Bitesize.

A compound is a substance that contains atoms of two or more different elements, chemically joined together. For example, water is a compound of hydrogen and oxygen, chemically joined …

For example, this particle diagram shows helium in white and oxygen in red. The two red atoms are joined together but not to the white atom, so this is a mixture of two elements.

A pure substance made from more than one type of element chemically bonded together. Elements bond in fixed ratios and so can be represented by a chemical formula.

Chemists use symbols and formulae to represent elements and compounds. Word equations and balanced chemical equations represent the changes that happen in chemical reactions.

When drawing a diagram of molecules made from the atoms of more than one element, different sizes and colours can show the different elements.

There are different ways to separate mixtures, for example by filtration, crystallisation, distillation, or chromatography. The method chosen depends upon the type of mixture.

shows how many of each type of atom join together to make the units which make up the compound. For example, in iron sulfide every iron atom is joined to one sulfur atom, so its …

Formulations are complex mixtures of chemicals which have a specific use. Chromatography can be used to identify the substances present in a mixture of solutes.

KS3 Chemistry Atoms, elements and compounds learning resources for adults, children, parents and teachers.