How Dense Is Water?

All things, including water, can be measured in density. Density is how much stuff is packed into the same amount of space. So a cup of water compared with a cup of honey — which is more dense? It's the gloopy, thick honey.

Solid things, including your bones, can be measured in density. Nice, solid bones will be strong, less likely to break, and have high bone density. If you get enough calcium when you're young, your bones are more likely to be dense and strong for your whole life. So drink milk and eat other calcium-rich foods!

Make a Candy-Colored Rainbow

But back to our density rainbow: Plain water is less dense than water mixed with other stuff, such as dissolved candy (sugar). In this experiment, you'll dissolve small and large amounts of candy into water. Then you can carefully layer the different-colored waters in a glass.

The water that contains only two dissolved candies will float on top of the water mixtures that contain four, six, eight, and 10 dissolved candies. Why? The water mixtures that are less dense (fewer candies) will float on top of the layers that are more dense (more candies).

What you need:

• Water
• Microwave-safe measuring cup
• Microwave
• Five small cups
• A clear glass to display your rainbow
• A wide spoon
• Skittles in these colors: red, orange, yellow, green, and purple

What to do:

1. Warm a cup of water in the microwave for about 30 seconds. (Ask an adult for help with this step.)
2. Put 2 tablespoons of warm water into each of the five cups.
3. Cup 1 will be red: Add 2 red Skittles.
4. Cup 2 will be orange: Add 4 orange Skittles.
5. Cup 3 will be yellow: Add 6 yellow Skittles.
6. Cup 4 will be green: Add 8 green Skittles.
7. Cup 5 will be purple: Add 10 purple Skittles.
8. Allow the Skittles to dissolve in the cups for 1 hour. (It may take longer for them to dissolve. Using warm water will help.) Remove or ignore the waxy film that will float on the surface.
9. When the candies are entirely dissolved, begin with the purple cup. Pour the purple water into the clear glass.
10. Use the backside of a spoon with the tip touching the side of glass to carefully add each new layer of color, beginning with green. Slowly pour the green water over the backside of the spoon so the green water rests on top of — instead of mixing with — the purple water.
11. Repeat with the rest of the colors, in this order: yellow, orange, red.
12. Your rainbow won't last forever so enjoy it while it lasts!

© Loralee Leavitt. Used with permission.
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Reviewed by: Mary L. Gavin, MD
Date reviewed: January 2011