Classify the following as an element, compound, homogeneous mixture, or heterogeneous mixture:
A brown liquid, with one boiling point, which completely reacts with hot copper to form a copper nitride and a copper oxide
The brown liquid described in the question does not fit into any of the categories provided (element, compound, homogeneous mixture, heterogeneous mixture).
From the information given, it can be understood that the brown liquid is a chemical solution or substance that reacts with hot copper. However, the composition and nature of the brown liquid are not explicitly stated. Therefore, without further information, it is not possible to accurately classify it into any of the given categories.