Final answer:
Adding KCl to water results in the dissolution and hydration of ions, an endothermic reaction that absorbs heat and can cause a slight decrease in the temperature of the solution.
Step-by-step explanation:
When KCl (potassium chloride) is added to water, it dissolves by breaking into its constituent ions, potassium (K+) and chloride (Cl-). Each of these ions is surrounded by water molecules due to ion-dipole forces. This process is endothermic; it absorbs heat from the surroundings. Consequently, the dissolution of KCl in water can result in a decrease in the temperature of the solution.
At the microscopic level, the positive (hydrogen) end of water molecules is attracted to the negative chloride ions, and the negative (oxygen) end to the positive potassium ions. This process, known as hydration, reduces the strong electrostatic forces between the ions, allowing them to move independently in the solution, which increases the disorder within the system.
Therefore, as KCl dissolves in water, leading to increased disorder and the absorption of heat, we can expect a slight decrease in temperature, unless the solution is disturbed by external factors such as additional heating.