topic c8- chemical analysis

• purity

  when a substance has had nothing added to it (natural state)
• test for purity

  • boiling/ melting point can tell you how pure a substance is
  • closer the substances boiling/ melting point is to its pure-state boiling/ melting point, the closer it is to being pure
  • example= pure water boils at 100 degrees celcius, most tap water boils at a slightly different temperature
• formulations- definition

  mixtures with exact amounts of components
• formulations

  useful mixtures made with a purpose using a formula (recipe)
• formulations- examples

  • paint
  • pills/ tablets
  • fuels
  • cleaning products
  • fertilisers
  • food and drink
• the 4 gas tests are for

  • chlorine
  • oxygen
  • carbon dioxide
  • hydrogen
• chlorine- gas test

  • use litmus paper
  • turns white if chlorine is present
• oxygen- gas test

  • put a glowing splint inside a test tube
  • relight the splint if oxygen is present
• carbon dioxide- gas test

  • use limewater
  • turns cloudy if carbon dioxide is present
• hydrogen- gas test

  • hold a burning splint at the end of a test tube
  • a squeaky pop will occur if hydrogen is present
• paper chromatography

  a method used to separate the substances in a mixture
• paper chromatography

  
• paper chromatography

  1. draw a pencil line where the substances start
  2. between the edge of the paper and the line, place the paper into the water
  3. the water begins to go up the page and spread the substances out
  4. once the process is complete- calculate Rf values
• Rf=

  substance distance (B)/ water distance (A)
• paper chromatography- Rf values

  • values should be between 0 and 1
  • if not you have got the numbers the wrong way around
• paper chromatography

  Rf- values