The substances in a mixture are not chemically bonded together and therefore can be separated using a variety of techniques, depending on the compounds and elements that make up the mixture. Magnets can be used to separate a mixture of nails that is made of iron and aluminum. Some mixtures made up of liquids and solids can be separated using filters. Distillation is a process used to separate substances that have different boiling points, like water and salt. A centrifuge is a machine that spins mixtures at high speeds. It can be used to separate substances by their densities.