chemical analysis

• A pure substance is a substance that is made up of only one compound or one element. A chemically pure substance will melt and boil at a specific temperature. You can test the purity by comparison.
• Impurities in a sample will lower the melting point and increase the melting range of your substance. It could also increase the boiling point and could result in your sample boiling over a range of temperatures.
• Formulations are mixtures of two or more substances that are designed to have a specific function. Each component is a measured quantity. For example, paint:

  • pigment - gives it colour
  • solvent - used to dissolve other components and alter viscosity
  • binder (resin) - forms a film that holds pigment together after painted
  • additives - to change physical or chemical properties
• Formulations are very important in pharmacy - it can change how a pill delivers the drug to what part of the body, and alters its shelf life. In everyday life, formulations include cleaning products, fuels, cosmetics etc.
• Testing for chlorine


  Bleaches damp litmus paper, turning it white
• Testing for oxygen


  If you put a glowing splint inside test tube, it will relight.
• Testing for carbon dioxide

  Bubbling it in calcium hydroxide (limewater) causes it to go cloudy.
• Testing for hydrogen


  A burning splint in a test tube will produce a squeaky pop.
• Flame emission spectroscopy is used to identify the elements in a sample. As ions heat up, electrons become excited and jump energy levels. When they drop back, they emit light. The light passes through a spectroscope, which can detect different wavelngths.
• It could look like this:

  
• The combo of wavelengths emitted by an ion depends on its charge and electron arrangement. The intensity indicates the concentration of that ion in the solution.
• Flame emission spectroscopy can be used to identify different ions in a mixture, making them more useful that normal flame tests.
• Instrumental analysis advantages - like flame emission spectroscopy

  • very sensitive
  • very fast
  • very accurate