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Make a Levitating Ice Cube
In this science experiment, kids will learn to make an ice cube "magically" float halfway up a glass while exploring the densities of liquids and solids.
When water freezes, unlike most liquids, it becomes less dense. Less dense solids and liquids will float on top of more dense liquids, and sink into less dense liquids. How well something floats is called “buoyancy.”
In this experiment, the baby oil is less dense than the vegetable oil, so it floats on top. Water is more dense than the vegetable oil, so it sinks to the bottom. In ice form, the cube is more dense than the baby oil, so it sinks through that layer, but less dense than the vegetable oil, so it floats between the two. But, when the cube melts into a liquid, the water drops are more dense than the vegetable oil , so the drops sink all the way to the bottom.
Materials
Instructions
Fill one of the glasses with water and add an ice cube. What happens? The ice cube should float on top. Why? Because the solid form of water (ice) is less dense than the liquid form.
Next, place a few drops of food coloring in the bottom of the second glass. Fill the glass about 1/3 full with baby oil. What happens? The baby oil is less dense than the food coloring, so it floats on top.
Next, gently add vegetable oil until the glass is about 2/3 full. What happens? The vegetable oil is less dense than the baby oil, so it floats on top.
Finally, gently drop in an ice cube. What happens? The ice cube is more dense than the vegetable oil, so it sinks, but less dense than the baby oil, so it floats between the two oils!
But keep watching – as the ice cube melts, the water, which is more dense than the baby oil, drops to the bottom and combines with the food coloring!
For younger children, this activity is best done as a demonstration.
Note: We had a hard time doing this activity with generic store brand baby oil. It worked well with Johnson's Baby Oil.
