The change a calcium chloride crystal undergoes is called crystallization. This refers to the process of forming a solid with a highly ordered, repeating, three-dimensional structure.

Here's a breakdown:

* Calcium chloride (CaCl2) is a salt that exists in solid form as crystals.

* Crystallization is the process by which these crystals form from a solution. This can occur by:

* Evaporation: As water evaporates from a calcium chloride solution, the concentration of dissolved calcium chloride increases, eventually reaching a point where it can no longer stay dissolved. The excess calcium chloride then precipitates out of the solution and forms crystals.

* Cooling: As a calcium chloride solution cools, the solubility of calcium chloride decreases. This means that less calcium chloride can stay dissolved at lower temperatures. The excess calcium chloride precipitates out of the solution and forms crystals.

So, while we might say a calcium chloride crystal has undergone "crystallization," that term is more broadly applied to the process of forming crystals in general.