Things you need:

• Diapers – different sizes, different brands
• Measuring cup
• Scissors
• Water

The experiment:

Open up the diaper like you are going to put it on a baby. Then fill the cup with water and slowly pour the water onto the diaper. What happens? Keep pouring water onto the diaper until it no longer absorbs any more. How many cups of water did you use? Try using different brands of diapers. Which one works the best, or holds the most water? If you can find a cloth diaper, compare how much water the cloth diaper can hold with how much the disposable diapers hold.

How does it work?

How the diaper works is, is has a polymer embedded in the filling of the diaper. A polymer is a large organic molecule formed by linking many smaller molecules (monomers) together in a regular pattern. Think of a singe paper clip as a monomer, or a simple molecule. Then link together long chains of the same paper clip, this would be a polymer. The polymer in the diaper, called sodium polyacrylate, works like a sponge, only a LOT more absorbent, it can absorb 200-300 times its mass in water. The polymer starts off looking like a powder, when it grabs onto the water, it expands into jelly-like crystals. Sodium polyacrylate is very hydrophilic - it attracts water.

There are many other polymers that you use everyday. Many polymers, such as polyethylene and polystyrene (used in trash bags, plastic bottles, and Styrofoam®, for example) are hydrophobic, meaning they repel water. Other common polymers include Jello, Silly Putty, as well as naturally occurring polymers like amber and cellulose (wood and paper).

What if you…

• Use warm water?
• Use ice cold water?
• Will diapers absorb other liquids?

---