Question

Which of the following is true about pure substances?
A.
A pure substance has the same chemical properties throughout.
B.
A pure substance can only be made up of one kind of atom.
C.
A pure substance can always be separated by physical means.
D.
All pure substances are unable to be separated by any means.

Answer 1

A is correct.

Explanation:
- A pure substance has a uniform (same) composition and thus the same chemical properties throughout.
- B is false: pure substances include compounds, which contain more than one kind of atom.
- C is false: pure substances cannot be separated into other substances by physical means if they are elements or compounds; compounds require chemical (not physical) separation.
- D is false: some pure substances (compounds) can be separated by chemical means.