write  an activity  to  show that  salt  contains  air?

$$\begin{gathered} Salt from sea water have many impurities in it. To remove these impurities, the \\ crystallisation is used. Crystallisation is a process that separates a \\ pure solid in the form of crystals from a solution. Some impurities may remain dissolved \\ in the solution even after filtration. That is removed by the evaporation. So the evaporation \\ removes some of the volatile impurities. This shows air is present in the salt. \end{gathered}$$

Take some salt in a china dish and add water and heat the solution. The solution is filtered and the filtrate is collected and evaporated.