What does "very little rock on the surface of the earth has remained fixed in its original rock type" mean?

How might this scientific phenomena be explained? a paper clip floats on water.

What is the number of neutrons in an atom with atomic mass of 35

You wish to prepare a buffer consisting of acetic acid and sodium acetate with a total acetic acetate plus acetate concentration of 250 mm and a ph of 5. what concentrations of acetic acid and sodium acetate should you use