Mixing calcium chloride and water is a chemical reaction. Calcium chloride is an ionic compound, which means it is composed of positively charged calcium ions (Ca2+) and negatively charged chloride ions (Cl-). When calcium chloride is dissolved in water, the ions separate and become surrounded by water molecules, a process known as ionization. This process is accompanied by the release of heat, indicating that the reaction is exothermic. The chemical equation for this reaction can be written as:

CaCl2 (s) + 2H2O (l) → Ca2+ (aq) + 2Cl- (aq) + 2H2O (l)

In this equation, (s) denotes a solid, (l) denotes a liquid, and (aq) denotes an aqueous solution.