Matter is made up of small particles called atoms. Atoms can exist on their own or together as molecules. Atoms are very small and around 100,000,000 of them end to end would measure 1 centimetre.

This article was first published in 2018 and last updated in 2023. At some point in secondary school you will need to choose your GCSE options. This can seem scary at first, but it’s all about ...