Explanation:
The generated Na+ and OH-ions are immediately surrounded by molecules of water (typically 6, each). There is the development of the exothermic hydration sphere for each ion. It seems as though there is negative overall energy of dissolving solid NaOH.
Now, since this dissolution is exothermic the temperature of the mixture rises.
Throw it in the ocean lol
An open system<span> is a system that has external interactions.</span>
It can be separated by physical means and is not uniform in composition.