How do you know if your chicken soup is safe to eat?

Well if its changing colors and its turned black or white its most likely mold. Which is bad because mold is not healthy for your body.

-----> If the shape has changed(gone sloppy, softer/harder, decreased weight rapidly without eating it), colour (could be green,white,black), if it stinks(more than it had before) or if you buy food which has expired it's date

these types of food have gone off/expired.