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Flame test for potassium. Footage of a bunsen burner flame being used in a flame test to identify a sample containing the metal element potassium. The sample (on a wire loop) is heated in the blue flame. The resulting pale purple (lilac) colour is due to the excitation of electrons in the metal by the heat of the flame. As these electrons lose their energy, they emit photons of light. The colour of the flame is different for different elements and can be used to identify unknown substances.
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