A drop of olive oil of radius 0.25 mm spreads into a circular film of diameter 20 cm on the water surface . Estimate the size of an oil molecule .

Suppose the film is one molecule thick. If d is diameter of an oil molecule, then
d=volume of oil drop/area of the film=[{4pi(r)^3}/3]/pi R^2=(4 r^3)/3 R^2
d=[4{0.25 * 10^(-3)}]/3(0.1)^2=2.08 * 10^(-9)