@ oil and water

You will need the following materials:

• ¼ cup (60 ml) water
• ¼ cup (60 ml) vegetable oil
• a small glass
• food coloring

First pour the water into the glass. Add a couple of drops of food coloring and mix. Next add the oil. What do you see? Which layer is on top?

Tightly cover the glass with plastic wrap or your hand (if it's big enough). While holding the glass over a sink (in case you spill), shake the glass so that the two liquids are thoroughly mixed. Set the glass down and watch what happens. Do oil and water mix?

The word “miscibility” describes how well two substances mix. Oil and water are said to be “immiscible,” because they do not mix. The oil layer is on top of the water because of the difference in density of the two liquids. The density of a substance is the ratio of its mass (weight) to its volume. The oil is less dense than the water and so is on top.

The next experiment examines the miscibility and density of several liquids.