Rocco loves making spaghetti with his grandmother. They make homemade tomato sauce by adding pureed tomatoes, sugar, salt, olive oil, and water. He notices that after he stops stirring, he sees a greasy film at the top of the red liquid. What does this tell you about his sauce mixture?
Oil floats on water because it is less dense I believe. So that would be the oil on top of the sauce(the oil is on top because of the water that was also added).