What happens if you add a hot substance of water to a cold substance of water? will the water become cooler or warmer?

Well if you are adding hot water to a cold  water would become warmer

Logically, if you add something that is cold to an already hot substance, it can't get warmer because the substance added was cold. Therefore, the substance as a whole can only get cooler.

Like if you add ice to a hot glass of water, the substance as a whole will get cooler because the original substance was hot, and the substance added was cool.