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Purpose
To determine the amount of distilled water that a high-absorbency disposable diaper will hold.

Procedure
1.	Remove the top and one side from the box.
2.	Use scissors to cut a hole about the size of a quarter in the center of the diaper's plastic outer covering.
3.	Drape the diaper, plastic covering down, across the top of the box and secure the ends of the diaper to the top edge of the box with the clothespins.
4.	Place the bowl inside the box directly under the hole in the diaper.
5.	Fill the measuring cup with distilled water.
6.	Slowly pour the water over the inside surface of the diaper from one end to the other.
7.	Continue to pour water into the diaper until water begins to drip out the hole cut in the plastic covering and into the bowl.
8.	Record the total amount of water poured into the diaper.

Note:Dispose of all diaper material in the trash. Do not put any material down the drain.

Results
The diaper tested by the author held 5 cups of distilled water. Note: The amount of water will vary with the brand of diaper used.

Why?
Sodium polyacrylate is a polymer (large, usually chainlike molecule made by combining smaller molecules). It is manufactured by the polymerization (process of joining small molecules to form a large molecule) of a mixture of sodium acrylate and acrylic acid. As water is added, it is immediately absorbed by a process called gelling. The ability of the polymer to absorb excessive amounts of water is due to osmotic pressure (the movement of water through a membrane permeable only to water). Water moves from an area of high water concentration to an area of lower water concentration. The difference in water concentration between the inside of the polymer and the pure distilled water surrounding it is due to the concentration of ions (charged particles, in this case, of sodium and polyacrylate) inside the polymer. The polymer continues to absorb water until an equilibrium is reached where the water concentration inside the polymer equals that of the water solution in which it is immersed.