Mixtures

• A pure substance consists only of one element or one compound.
• A substance made of one type of atom only is referred to as an element.
• A substance formed by the chemical union of two or more elements is referred to as a compound.
• A mixture is two or more substances that are not joined together.
• The substances in a mixture can be elements, or compounds, or both.
• Being part of a mixture does not change the chemical properties of the substances that are in it.
• Mixtures can be separated by physical processes.
• The components of a mixture can be separated without chemical reactions.
• Pure substances and mixtures can be separated using methods such as filtration, crystallisation, simple distillation, fractional distillation and chromatography.
• The method chosen to separate a mixture depends on the type of mixture.
• The term 'pure' is used in chemistry in a different way from its everyday meaning.