States of Matter and Mixtures: Purity

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.