Experiences

Colorful flames

Josep Bernardo i Vera

Spain

High Secondary School

Chemistry

Laboratory

Direct

The emission spectra are characteristic of each element and allow its identification. This property can be qualitatively determined by a simple experience that allows recognize the presence of certain metals by the color formed by exposing its compounds to a flame.
The flame test for the detection of metals (sodium, calcium, lithium, strontium, barium, potassium, copper ...) is based on the fact that the outer electrons of the metals or their ions undergo electronic transitions (when they are heated by the flame ) that cause light emission of the characteristic emission spectrum of each metal.
To make this experience it is necessary to prepare different saturated solutions of sodium chloride, calcium, lithium, strontium, barium, potassium, copper... in few milliliters of ethanol. Each of these solutions are separately poured into different crucibles. Set fire to them and flames of different colors appear, corresponding to the characteristic light emission spectrum of each metal.
Compounds and metals have the characteristics colors of the metals and allow a qualitative detection of these metals and compounds in mixtures.
This experience allows students to better understand the emission expectra.