You will need:
• Filter paper
• A glass
• Sketch pens or whiteboard markers
1. Stick strips of filter paper on a long pencil.
2. Make a big dot, each a different colour, towards the end of every strip.
3. Place the pencil on the glass, letting the filter paper strips hang down into it.
4. Fill the glass with water, until the ends of the strips are just touching the water.
5. Wait for a while, and you’ll see interesting things happen on the paper strips.
6. The coloured dots will seem to have climbed up the paper and settled themselves at different heights. Darker shades like black and brown, will seem to have divided themselves into different colours!
Why dark dots change colour:
The process that separates mixtures into their individual components is called chromatography. A mixture contains different types of molecules. The speed with which these molecules react to water (called solubility) usually varies. Chromatography uses this property of liquids to separate them. So as the filter paper absorbs water, dark dots separate into the various colours that make them up.
Now that you’re aware of this fascinating effect, you can create interesting patterns using chromatography.
1. Make a small hole in the centre of a filter paper disc.
2. Draw five or six coloured dots around the centre, spaced apart.
3. Fold a tissue paper into the shape of a cone, and insert the tip of the cone through the hole in the disc.
4. Keep this contraption in a glass of water, such that the base of the tissue paper cone touches the water.
5. You will notice beautiful patterns emerge on the disc. Arrange the dots differently to get different patterns.
Try the chromatography experiment with leaf pigment instead of ink. You can extract the pigment by placing the leaf on filter paper and rolling a coin over it. When you lift the leaf, you’ll notice that the green colour from the leaf has made an impression on the filter paper below. Try to get as much of the green on the paper as you can.
At the end of doing the experiment, you will notice that it’s not just shades of green that appear. There are also shades of yellow and sometimes, orange and red. All these pigments are present in leaves, apart from chlorophyll. The only times they are visible, though, is in autumn, when chlorophyll breaks down and allows the other pigments to be seen.