Is steel a mixture or pure substance

In the millikan oil drop experiment they determined that every drop had a charge which was a while number multiple of -1.60x10^-19. if a drop has a total charge of -9.60x10^-19 then how many excess electrons are contained within the drop?

Define a is a tiny pavket of energy

Which of these expressions are correct variations of the combined gas law? p1v1t2 = p2v2t1 both