The process of a substance dissolving in water and causing the temperature to increase is called exothermic dissolution.

Here's why:

* Exothermic reactions release heat into the surroundings, causing the temperature to rise.

* When a substance dissolves, the process involves breaking bonds in the solute and forming new bonds with water molecules (hydration).

* If the energy released during bond formation (hydration) is greater than the energy required to break bonds in the solute, then the overall process releases heat, making it exothermic.

Example: Dissolving sodium hydroxide (NaOH) in water is exothermic. The heat released can cause the solution to become quite hot.