Question

Which method would be best to separate a mixture of oil and water?

separation by density
separation by particle size
filtration
distillation

Answer 1

separation by desity because oil is much heavier then water so it would go to the bottom

Answer 2

generally speaking oil will float on water, hence oil slicks at sea

this is due to their differing densities, oil is generally less dense than water and so it floats on water all things being equal.