Purity: Criteria of Purity

Purity: Criteria of Purity

Criteria of Purity

Concept of Purity

  • Learn the definition of pure substance. It is made of only one type of particle.
  • Know the difference between pure substance and mixture. Mixtures contain two or more types of particles mixed together.

Methods to Check Purity

  • Recognise the use of melting point and boiling point to check purity. Pure substances have sharp, fixed melting and boiling points.
  • Understand the concept of chromatography. This technique separates the different components of a mixture to check it for purity.

Impurities Impacting Physical Properties

  • Understand how impurities often lower the melting point and increase the boiling point of a substance.
  • Learn how slight impurities can significantly modify the physical properties of a substance such as its colour, taste, melting point, boiling point, and electrical conductivity.

Interpreting Chromatograms

  • Be able to read a chromatogram, observing the travel of different substances along the medium to identify them.
  • Understand how substances in a mixture are identified from their relative positions, or Rf values, obtained using a reference in chromatography.
  • Be aware that substances in a mixture move faster if they have a higher affinity for the medium, which can help in their identification.

Purity in the Industry

  • Recognise the importance of producing and using pure substances in various industries, such as pharmaceuticals and electronics, for performance and safety reasons.
  • Understand the need for rigorous quality control tests, including those for purity, in commercial production processes.
  • Appreciate the role of precise scientific techniques in measuring purity to ensure consistency and maintain standards in industries.