If a compound is separated into separate parts does the substance remain the same substance

Why does a cake rise when you bake it? ♡

What does a particular point on a line of a phase diagram represent? o a. the maximum temperature a substance can exist at without bonds breaking b. the pressure created by the kinetic energy of molecules at a particular temperature c. the melting point or boiling point of a substance at a specific pressure d. the conditions in which temperature and pressure have equal effects on a substance

How many moles of magnesium is 3.01 x10^22 atoms of magnesium?