Flames of different substances __________ colours.
2, 3, 4 and 5
Flame colour may be different for different substances because on burning they emit waves of different wavelength due to differences in their atomic structures. This is actually a characterstic property of materials. For example, Sodium on burning emits a yellow flame while Potassium emits a lilac flame. This property is utilized in flame tests to determine the elemental composition of materials.