To find the number of components in a food colour or coloured mouth fresheners like fennel seeds, we use the technique of paper chromatography. This method separates the components of a mixture using differences in their interactions with the solvent and the paper, separating them based on how fast they move.

First, take a 3 cm wide strip of chromatographic paper or filter paper. Draw a straight, horizontal line 2 cm from the bottom. Mark a spot with the food colour or fennel seed extract at the centre of this line. Place the paper strip vertically into a container like a gas jar, measuring cylinder, or beaker, ensuring the lower end dips into the solvent. The solvent level must be below the spot.

While water is a common solvent, you can use a 2% m/v salt solution for green food colour. In some cases, water may not work, and you might need a different solvent, such as alcohol or a mixture of solvents.

As the solvent rises through the paper, the colour starts to separate into different colour spots. The liquid carries the substances up the paper at different speeds. The number of distinct colour spots formed on the paper indicates the number of components present in the original mixture.