I have this question for chemistry, but can't know whether it is an impurity or not, please help.
closed as unclear what you're asking by Mithoron, aventurin, airhuff, Gaurang Tandon, Tyberius May 4 '18 at 2:58
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An impurity is pretty much by definition something that is present that is not desired. If you have deliberately added something, in this case instant coffee, then it is not an impurity but a component, something you intend to have present.