How does heterogeneous mixture differ from a pure substance?

Answer 1

A heterogeneous mixture contains multiple chemical substances combined in a non-uniform way, whereas a pure substance contains molecules with only one chemical identity. For example, salt is a pure substance, whereas a mixture of salt an rocks is a heterogeneous mixture.

Answer 2

A pure substancs doesn't contain impurities.
The components of a homogeneous mixture are not visible.
The components of a heterogeneous mixture are easily identifiable.