Layers Upon Layers: Testing How Objects Interact with Liquids

Research Question:

How does a liquid’s density affect how it interacts with other liquids and with any objects that are placed in it?

Materials:

• Clear cup or jar, 10-12 oz.
• 1/3c honey
• 1/3c vegetable oil
• 1/3c water
• Small coin
• Paper clip
• Small piece of cork
• Paper and pencil

Experimental Procedure:

1. Pour the honey, the vegetable oil, and the water into the cup in that order, and set it on a flat surface where it won’t be disturbed. Wait several minutes to let it all settle.
2. Look at the liquids in the glass. See how they’ve formed three different layers? That’s because the honey is more dense than the water, and the water is more dense than the oil, so they don’t mix easily and tend to separate when they can. Draw a big picture of this on your piece of paper, labeling the layers.
3. Now gently drop the coin into the cup (a penny or dime works best). Where does it end up? Do the same thing with the paper clip and the piece of cork. Do they go where you expect them to? If you like, you can drop a couple of other small objects in the cup and see what happens.
4. Now look at the cup and think about why the objects ended up where they did. Can you think of a reason? Draw a picture of the cup with the objects in it, showing where each one ends up.

Terms/Concepts: density, fluids, fluid dynamics

References: Phineas and Ferb Science Lab, published by Scholastic, Inc., pp. 28-29 (2011).