Final answer:
The process of a powder turning into a lump due to exposure to moisture is called deliquescence. Deliquescence occurs when a hygroscopic substance absorbs moisture from the air until it forms a solution.
Step-by-step explanation:
The process of a powder turning into a lump due to exposure to moisture is known as deliquescence. This phenomenon occurs when a substance absorbs moisture from the air until it dissolves in the absorbed water and forms a solution.
Deliquescence is different from hydration, which is the process of solute particles being surrounded by water molecules. It is also distinct from flocculation, which involves the clumping together of particles in suspension, and from desiccation, which is the removal of moisture, as in drying or lyophilization.
An example of a substance that exhibits deliquescence is calcium chloride (CaCl2), which is often used as a desiccant because of its strong moisture-absorbing properties.