A salt that absorbs water is called a hygroscopic. Calcium dioxide is an example of such a type of salt. Hygroscope is the phenomenon of inviting and carrying water molecules through absorption from the surrounding environment, usually at average room temperature. Suppose water molecules become suspended among the substance’s molecules.
In that case, absorbing elements can become physically changed, changing in volume, boiling point, viscosity, or some other physical attribute or property of the substance. Hygroscopic substances consist of cellulose fibers, like cotton and paper, sugar, caramel, honey, glycerol, ethanol, methanol, wood, sulfuric acid, many fertilizer chemicals, many salts, and a myriad of other items.
The quantity of moisture held by hygroscopic materials is proportional to the relative humidity. Hygroscopic also plays a crucial role in the manufacturing of plastic items. Some plastics are hygroscopic, although others are not.