Some of the different substances that make up a pizza are cheese, dough, pepperoni, sauce, and sausage.
A pure element or compound contains only one substance, with no other substances mixed in. Impure materials may be mixtures of elements, mixtures of compounds, or mixtures of elements and compounds.
Food and drink may be advertised as ‘pure’. For example, you may see cartons of ‘pure orange juice’ or ‘pure mineral water’. This means that nothing else was added to the orange juice or mineral water during manufacture. However, these substances are not pure to a scientist. In science, a pure substance contains only one element or compound.
Learn more about pure and impure chemical substances at BBC Bitesize.