EXAMPLES:Oil and water - In an oil spill in the ocean, the oil rises to the top because it is less dense than water.
A Styrofoam cup is less dense than a ceramic cup, so the Styrofoam cup will float in water and the ceramic cup will sink.
A piece of wood will float on water; but, most rocks are more dense than water, so they will sink.
Helium is less dense than air, so helium balloons rise.
Oil floats on vinegar because its density is less.
When adding motor oil to your car, you need to know the recommended density.