Activity 2.9 NCERT Class 9 Science Chapter 2 Is Matter Around Us Pure
Activity 2.8 wants us to separate impurity from copper sulphate by heating its solution.
Pure Copper sulphate forms as a crystal.
Crystallisation is a property of some salts. In an over-saturated solution of the salt, molecules of salt join to form small clusters. These small clusters have a fix molecular arrangement. We call such clusters as crystals.
Here we heat a solution of copper sulphate. Heating produces a saturated solution of the salt. When this solution cool, oversaturation results in the formation of copper sulphate crystals. Molecules of a crystal do not contain any impurity. As a result, we get pure copper sulphate.