1. What is the independent variable?
2. What is the dependent variable?

-The independent variable is a variable often denoted by X, whose variation does not depend on that of another.

-The dependent variable is a variable often denoted by Y, whose value depends on that of another.

pure substance: iron,copper

impure substance: water,charcoal

i don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.