Ammonium chloride (NH₄Cl) dissolving in water is an endothermic process. This means that the process absorbs heat from the surroundings, making the solution feel cold. Here's why:

* Breaking bonds: When ammonium chloride dissolves, the ionic bonds between ammonium ions (NH₄⁺) and chloride ions (Cl^-) in the solid are broken. This requires energy, which is absorbed from the surrounding water.

* Formation of hydration shells: The released ions then become surrounded by water molecules, forming hydration shells. This process also requires energy.

* Overall energy change: The energy required to break the bonds and form hydration shells is greater than the energy released in the formation of ion-dipole interactions between the ions and water molecules. This means the overall process absorbs energy from the surroundings, making the solution feel cold.

In summary, the cooling effect is a result of the energy required to break the bonds in the ammonium chloride crystal and to form hydration shells around the ions.