What are unwanted materials mixed in water called?

Unwanted materials mixed in water are referred to as contaminants or impurities because they detract from the water's purity and safety for various uses. Contaminants can include substances such as chemicals, biological agents, or particulate matter that compromise water quality. This definition encompasses a wide range of pollutants, from harmful bacteria to industrial pollutants, which can have detrimental effects on health and the environment.

The other options do not accurately describe unwanted materials in water. Water sources refer to locations where water is found, such as rivers or lakes, and do not signify the quality or purity of the water. Palatable substances are those that are pleasant or acceptable to taste or consume, which would not encompass unwanted materials. Gray water refers specifically to wastewater generated from domestic activities, such as laundry or dishwashing, that is not contaminated by harmful substances and can sometimes be reused, but it does not represent general impurities in water.