When an anhydrous salt retain water in the crystalline structure.
Sodium chloride (NaCl) is not a hydrated salt.
Hydrated salts appear dry because they have incorporated water molecules within their crystal lattice structure. This water is not easily visible on the surface of the salt, giving the appearance of dryness. However, if the hydrated salt is heated or exposed to low humidity conditions, the water molecules can be released, causing the salt to become visibly wet.
Only some salts have hydrates, not all. These salts contain in the formula water of crystallization.
A hydrated salt contain water of crystallization.
You might be thinking of hydrated salts. Examples include hydrated Copper Sulfate (CuSO4 . 5H2O)
No, only some salts change the color after dehydration.
probably hydrated beryllium salts like BeCl2.H20
You might be thinking of hydrated salts. Examples include hydrated Copper Sulfate (CuSO4 . 5H2O)
Dehydration of hydrated salts is usually considered to be a physical change.
Anhydrous salts prepared by evaporating the water contained in a hydrated salt. However, anhydrous salts are non-electrolytes, meaning they can't pass an electric current.
Examples: MgSO4.2H2O, UO2(NO3)2.6H2O, NaCl.2H2O etc.
On heating, hydrated salts lose their water of crystallization and as a result, the crystals lose their shape and colour and change to a powdery substance.