Question

When oil spills in the ocean , why does the oil float on the water

Answer 1

because of the certain chemicals it has in it, those chemicals dont combine with the water

Answer 2

Oil+ water= do not mix
Like dissolves like.
Substances dissolve another substance if the molecules have similar properties, also because of something called the buoyancy force(force that causes some items to float in water)
Remember: oil is less dense than water.