To carry out flame tests with salts of lithium, sodium, potassium, barium, strontium and copper.

Procedure

  1. Light a bunsen burner and adjust it to obtain a blue flame.
  2. Dip the wooden splint in water and add one of the salt to it so it sticks on.
  3. Place the wooden splint over the flame to observe the colour of the flame.
  4. After the salt has finished burning put the flame out and take note of the colour.
  5. Repeat this for all the different salts.

Results

  • LithiumDeep red
  • SodiumYellow
  • PotassiumLilac
  • BariumGreen
  • StrontiumRed
  • CopperBlue-Green

Notes

  • As the excited electrons fall to the ground state, they release energy in the form of light which gives each metal salts their characteristic colour.
  • To determine the metal salt of an unknown substance compare the colour of the flame with a known salt.
  • To prevent cross contamination use separate wooden splints.
  • Uses: These salts are used in fireworks to release flares of different colours.

Video demonstration

http://www.youtube.com/embed/5BI6qXaJtuo

Aaron Keller, Chemistry Teacher, demonstrates the different colours that can be produced in a flame by the use of different metallic salts. When ions of the metallic elements in each salt are heated their electrons become excited. Excited electrons drop back down to lower energy levels and release light of very specific colours in the process. This makes for a beautiful demonstration and colourful fireworks.