Define the terms efflorescence and deliquescence.

Efflorescence and deliquescence are two distinct phenomena related to the behavior of certain substances, particularly salts, in the presence of moisture or water:

Efflorescence:
Efflorescence refers to the process in which soluble salts present in a solid material, such as concrete, masonry, or soil, migrate to the surface of the material and form a white, powdery or crystalline deposit when water evaporates. This typically occurs when water from the surrounding environment penetrates the material and dissolves the salts within it. As the water evaporates from the surface, it leaves the salts behind, leading to the formation of efflorescence. Efflorescence is a common issue in construction materials and can affect the appearance and durability of structures.

Deliquescence:
Deliquescence is the opposite of efflorescence. It is a process in which a hygroscopic substance absorbs moisture from the surrounding air and forms a concentrated solution, ultimately dissolving in the absorbed water. When a substance deliquesces, it becomes a liquid or a solution of the dissolved compound. This phenomenon is often observed in certain salts, such as calcium chloride and potassium hydroxide, which readily absorb moisture from the atmosphere and become liquid when the humidity is high. Deliquescence is particularly relevant in industries like chemistry, agriculture, and chemical storage, where moisture-sensitive materials need to be handled and stored appropriately to prevent deliquescence-related issues.

In summary, efflorescence involves the migration of salts to the surface of a material as water evaporates, leading to the formation of a visible deposit, while deliquescence is the process by which a hygroscopic substance absorbs moisture from the air and becomes a liquid or concentrated solution. Both phenomena are influenced by the presence of water and can have practical implications in various fields.