What effects, if any, do impurities have on the boiling point of water?
The impurities are normally killed at boiling point (a little over) of water. This renders them harmless.
Impurities like bacteria and other pathogens typically die at the boiling point of water or a little above, like
This is known as sterilizing water and is used as a precaution in many situations.
When sterilizing water, the heat denatures the DNA (the nucleic molecule) by breaking the hydrogen bonds holding the protein structure in shape.
At this stage, pathogens are rendered harmless.
Keep in mind that there are thermophiles that strive in extreme temperatures.
Hope this helps :)