Activity 3.13 NCERT Class 10 Science, Chapter 3 Metals and Non-metals
Activity wants us to find the various properties of various salts like physical nature, melting point, solubility, conduction of electricity.
Salts of acids and bases are Hard; brittle; have a high melting point; soluble in water; insoluble in non-polar solvents like kerosene, benzene; conducts electricity.
Molecules of salt are closed together by the strong Ionic bond between anions and cations. This strong attraction gives a salt hard appearance, high melting and boiling point.
In water and other polar solvents, they form strong ionic bonds, so they are soluble in water. Non-polar solvents like organic solvents and kerosene do have polar bonds. A salt molecule, therefore, does not mix with such solvents. As a result, it sinks to the bottom.
In solution form molecules of salts are in ionic form. They move freely in the solution; therefore they conduct electricity.
For any doubt, think about sodium chloride and solve the question.