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. Provide the students with a variety of liquids, such as corn syrup, lamp oil, and milk. Ask them to predict what will happen when the three liquids are combined. Have the students discuss this in small groups.
Students record their data on the attached data sheet.
Then, have them develop additional questions and choose one to investigate. Have the students weigh 10 mL of each liquid. Provide a data sheet that they can record their findings on. Show students a glass of fresh water and a glass of salt water. Have them test their predictions.