If the temperature of water decreases when a compound is dissolved, what type of process is occurring?

When the temperature of water decreases upon dissolving a compound, this indicates that the system is absorbing heat from the surroundings. In thermodynamics, this is characteristic of an endothermic process. During an endothermic reaction, energy is taken in, resulting in a drop in temperature of the solvent—in this case, water.

The process involves the breaking of bonds or interactions between the solute particles and the solvent molecules, which requires energy. As the compound dissolves and absorbs heat from the surrounding water, the overall temperature of the solution decreases, demonstrating that the dissolution is endothermic.

This behavior is in contrast to exothermic processes, where heat is released, leading to an increase in temperature. Hydration refers to the interaction of water molecules with ions or molecules during dissolution but does not directly describe whether the process is endothermic or exothermic. Condensation, which involves a temperature decrease as a gas turns to a liquid, is also unrelated to the dissolution process being described. Hence, the correct classification of the process being observed when the temperature of water decreases upon the dissolution of a compound is indeed an endothermic process.