Fill a clear glass bowl or container a little more than halfway full with tap water. Add one or two drops of blue food coloring to mimic the color of the ocean. The blue will also provide a contrast when you add the oil to simulate an oil spill.
Pour several tablespoons of cooking oil into the container, enough so that about an inch of oil floats on top of the water. The cooking oil will simulate what happens when an oil tanker or offshore well leaks oil into the ocean.
Stir the water vigorously with a wooden spoon or, if the container has a lid, shake the container to mix the oil and water to demonstrate the relationship between the two liquids. Show your classmates that even after mixing, the oil and water will separate, with the oil floating on top of the water.
Dip a feather in the oil-capped water to illustrate how oil spills affect birds and other marine wildlife. When you remove the feather from the container it will be coated in a slick layer of oil. Provide some information about how oil spills pose a threat to marine animals.
Soak up the oil on the surface of the container with cotton balls. This simulates human efforts to clean up real oil spills. It will be difficult to catch all of the oil with the cotton balls, which proves that point that real oil spills are not easily cleared and can leave a lasting environmental impact.