States of Matter and Mixtures: Purity

Matter exists in three states: solid, liquid, and gas. Each state has distinct properties. Solids have a definite shape and volume, liquids only have a definite volume, and gases have neither a definite shape nor volume.
When a substance is pure, it means it consists of only one type of atom, molecule, or compound.
Mixtures contain two or more different substances that are not chemically bonded together.
Purity can be determined using a number of different methods. Melting and boiling points are common methods used. A pure substance has a specific melting and boiling point, whilst mixtures will melt or boil over a range of temperatures.
Chromatography is another method of determining purity. This separates the components of a mixture and can identify substances based on their rates of movement under the influence of a liquid or gas.
An impure sample will show varying colours or levels of intensity within individual spots on a chromatograph. Pure samples will only show a single spot.
Even when a substance appears pure, it’s possible for it to be a mixture on a microscopic level. Ultra-pure substances are rare and typically only found in laboratory conditions.
A formulation is a mixture that has been created for a particular purpose, with specific proportions of its different components. Examples include fuels, cleaning products, paints, medicines, alloys, and fertilisers.
Each component in a formulation contributes to its overall function. Changing the proportions often alters the functionality.
The Earth’s resources provide useful, but raw materials that often require chemical processing to become useful. Some resources are finite and will not be replaced within a human timescale. Sustainable methods of extracting, using and disposing of these are necessary.