Activity 2.7 NCERT Class 9 Science Chapter 2 Is Matter Around Us Pure
Activity 2.7 asks us to separate the ink dye from the paper using chromatography technique.
Observation:
The dye moves upwards and separates into different colours.
Explanation:
An ink dye consists of several colours. These different dyes have different solubility. Dye with higher solubility in water dissolves quickly and move fast with the water. As a result component of the dye separate with each other.
Inference/conclusion:
When components of a mixture have varying solubility, we can separate them using chromatography.
Some facts:
Water rises in the paper due to capillary action. The force of attraction between the paper and water is more than between two water molecules. It creates a pulling pressure on the water. It results in the rise of water.
Chromatography is usually used for coloured substances which we can visually examine by the pattern they form. So, we call them chromatography.
A chromatographic pattern of a substance is characteristic of that substance.
Chromatography is a costly method. We use it in separating components of volatile oils to make expensive perfumes.
Next: Separation of a mixture by distillation, Activity 2.8.
See also: Separation of immiscible liquid by separating funnel, activity 2.6.
2.7 figure is separation of ammonium chloride and salt by sublimation ok .