How does adding salt water to fresh water alter the fresh water's physical properties?
When the salt water is added to the fresh water, they will evenly mix and form a new, diluted version of the original salt water solution. The properties of the new solution will be in between the properties of the fresh and salt water.
Ex: Freshwater doesn't conduct electricity super well. But once the salt water is added, the new solution will conduct electricity better than the freshwater.