1. Pure substances cannot be separated into any other kinds of matter, while a mixture is a combination of two or more pure substances.
2. A pure substance has constant physical and chemical properties, while mixtures have varying physical and chemical properties (i.e., boiling point and melting point).
3. A pure substance is pure, while a mixture is impure.
Answer:
the first energy level is closest to nuclear the second energy level is a little farther away than the first
My guess is b for the question
Physical change alters a given material without changing its chemical.