Answer:
C) pure substance
Step-by-step explanation:
Pure substance is any substance formed by only one type of molecule, of invariable and homogeneous chemical composition, which has constant physical and chemical properties. Pure substance may exist in more than one phase, but in such cases the phase composition will be the same.
In short, pure substance is all material with the following characteristics:
- Structural units (molecules, ionic assemblies) chemically equal to each other.
- Fixed composition, resulting in fixed properties such as density, melting and boiling point, etc. That is, these substance have distinct properties and composition that never vary.
- The temperature remains unchanged from the beginning to the end of all your physical state changes (melting, boiling, solidifying, etc.).