When calcium chloride (CaCl2) is dissolved in water, the water molecules surround and solvate the calcium and chloride ions. The positively charged calcium ions (Ca2+) attract the negatively charged oxygen atoms of the water molecules, while the negatively charged chloride ions (Cl-) attract the positively charged hydrogen atoms of the water molecules. This results in the formation of a hydration sphere around each ion.

The water molecules in the hydration sphere are held in place by electrostatic forces and hydrogen bonds. The strength of these interactions determines the extent of hydration. Calcium ions are more strongly hydrated than chloride ions because they have a higher charge density. This means that calcium ions are surrounded by a larger number of water molecules than chloride ions.

The hydration of calcium chloride lowers the freezing point of water and raises the boiling point of water. This is because the hydrated ions interfere with the formation of ice crystals and water vapor.