Final answer:
A heterogeneous element does not fit into the categories of substance versus mixture.
Step-by-step explanation:
In this question, the student is asked to sort a specific substance, which is a heterogeneous element, into the categories of substance versus mixture.
A heterogeneous mixture is a type of mixture where the components are not evenly distributed. An element, on the other hand, is a pure substance that cannot be broken down into simpler substances. In this case, a heterogeneous element does not fit into either category, as it does not meet the criteria of a pure substance or a mixture.
Therefore, the answer to this question is that a heterogeneous element is not classified as either a substance or a mixture. It is a unique category on its own.