Celebrate Science!
Try this National Science Experiment and report your findings at www.4-H.org.

Experiment: Helpful Hydrogels

Can hydrogels help the environment? Water is everywhere—in the sky, in the ground, and in our homes. However, caring for this vital resource is often a challenge for each of us. Conservation means using water wisely. Protecting our groundwater is important because it is a source for drinking and irrigation. Consequently, scientists and engineers have developed amazing, superabsorbent polymers, called hydrogels, that can help. Try this experiment with a parent or teacher and learn more about one particular hydrogel that is at work in millions of households.

YOU WILL NEED

• Disposable diaper
• Water
• Newspaper
• Scissors
• Measuring cup and measuring spoons
• Zip-lock bag—one gallon (3.8 liter) size
• Nine-ounce (266-ml) plastic cup

HERE'S HOW

Collect a sample of hydrogel from the cotton and plastic lining of the diaper.
1. Place the diaper on the newspaper. Carefully cut through the inside lining and remove all the cotton-like material. Put all the stuffing and plastic lining in the zip-lock bag.
2. Scoop up any of the powdery material that may be left on the newspaper and pour it into the bag with the stuffing. Blow a little air into the bag to make it puff up like a pillow, then seal the bag.
3. Shake the bag for a few minutes to remove the powdery hydrogel polymer from the stuffing. Notice how much powder falls to the bottom of the bag.
4. Carefully remove the stuffing and the plastic lining from the bag and check out the powdery polymer left in the bag. Repeat steps 1-4 with another diaper, if needed, to get one teaspoon (5 ml) of the hydrogel powder.
5. Pour one teaspoon (5 ml) of hydrogel powder into the plastic cup. Measure 1/2 cup (118 ml) of water, and pour into the cup.
6. After about 30 seconds, observe that the water has changed—it's no longer a liquid—it's a gooey solid!

Things to think about:

• How does this water-slurping powder work? Does it only absorb water?
• How much water will the average diaper absorb?
• What would happen if you let the gel dry out? Is this powder reusable?
• Besides diapers, how else could this powder be used?
• How does the absorbency of the hydrogel compare with other materials that are absorbent: cotton balls, paper towels, or sponges?
• How could adding other ingredients (like salt) affect hydrogel's water-absorbing properties?

So what's next?

Hydrogel technology, of which there are many different types, lends itself well to an unlimited number of agricultural and domestic applications. For example, certain growers have learned that by adding hydrogels to the soil in the right proportions, crops easily survive on 60-80 percent less water. Today, hydrogels are widely used in such applications as forestry, gardening, and landscaping as a means of conserving water. Go to 4-H.org to try the expanded student version of the experiment, find out more information, and join in a discussion about hydrogels.

Polymer facts
A polymer is a long chain of molecules. Polymers are all around us, and they make up materials like bicycle helmets, CDs, tires, plastic water bottles, rubber bands, and glue. The hydrogel polymers in this experiment are long molecule chains that grab onto water molecules—some can soak up as much as 500 times their weight in water!

Experiment and support contributed by 4-H, Dr. Bob Horton, 4-H science education specialist for The Ohio State University Extension, Carol Warkentien, Jeanne Gogolski, Steve Spangler, and members of the 4-H Science, Engineering, and Technology Leadership Task Force.