A liquid that is less dense will float on a liquid that is more dense. For example, a glassful of water has a greater mass than a glassful of oil. If you drop an object into the density column, where it rests can tell you about its density. When the same volume of milk, lamp oil, and corn syrup are combined in any order, three separate layers form. The reasoning for this is the three liquids have different masses, causing different densities.
Oil forms the top layer, milk the middle, and corn syrup the bottom.
When you drop a piece of cork into this density column, it will float on the oil. A piece of candle will sink below the oil but will float on the milk. A piece of metal will sink to the bottom of the column, therefore having the greatest density. When you slowly combine a glass of salt water with a glass of fresh water, two separate layers will form. The fresh water is less dense and will float on the salt water.