Flame Tests (Edexcel International A Level Chemistry)

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Philippa

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Philippa

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Characteristic Flame Colours

  • Metal ions produce a colour if heated strongly in a flame
  • Ions from different metals produce different colours
  • The flame test is thus used to identify metal ions by the colour of the flame they produce
  • Dip the loop of an unreactive metal wire such as nichrome or platinum in concentrated acid, and then hold it in the blue flame of a Bunsen burner until there is no colour change
  • This cleans the wire loop and avoids contamination
    • This is an important step as the test will only work if there is just one type of ion present
    • Two or more ions means the colours will mix, making identification erroneous

  • Dip the loop into the solid sample and place it in the edge of the blue Bunsen flame
  • Avoid letting the wire get so hot that it glows red otherwise this can be confused with a flame colour

Identifying Metal Cations, IGCSE & GCSE Chemistry revision notes

Diagram showing the technique for carrying out a flame test

Explanation for the occurrence of the flame

  • In a flame test the heat causes the electron to move to a higher energy level 
  • The electron is unstable at this energy level so falls back down 
  • As it drops back down from the higher to a lower energy level, energy is emitted in the form of visible light energy with the wavelength of the observed light

Colours Observed in Flame Tests

colours-observed-in-flame-tests

  • Mg2+ does not have an observed colour because the energy emitted during a flame test involving magnesium is outside the visible spectrum

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Philippa

Author: Philippa

Expertise: Chemistry

Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener.