CBSE Class 9 Answered

Solubility of a solute changes with change in temperature since the dissolution process of a solute in a solvent may be exothermic or endothermic. If the dissolution process of a solute in the solvent to make a solution is exothermic , the solubility of a solute decreases with increase in temperature. This is in accordance of le Chatleir's principle which you will study in higher classes.

If the dissolution process of a solute in the solvent is endothermic , the solubility of a solute increases with increase in temperature. This is in accordance of le Chatleir's principle.

why different colours present in the ink rise to different levels during paper chromatography???

This is beacuse of a phenomenon called adsorption. The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption.

Different colours are adsorbed on an adsorbent to different degrees.The more adsorbed colours travel very slowly and cover a less distance whereas the less adsorbed colours travel fast and more to a greater distance and hence can be separated.