Objective: Students will understand the importance of hydrogels and how they are
being utilized in water conservation efforts. Students will be able to demonstrate how
hydrogels are used through classroom experiments.
3 Teaspoons Water Jelly Crystals
8oz Tap Water
8oz Distilled Water
8oz Salt Water
3 Quart Sized Zippered Bags
Synthetic (man-made) polymers can be either hydrophobic (water fearing) or hydrophilic
(water loving)! Examples of synthetic polymers include plastic bags, plastic cups, and
plastic toys. An example of a synthetic polymer that loves water can be found inside a
diaper. An example of a natural hydrophilic polymer is cotton. It is the synthetic
hydrophilic polymer that is making big news. Superabsorbent polymers, called
hydrogels, are being used to help conserve water, sometimes by 80%! Some
hydrogels can absorb 500 times their weight in water! This superabsorbent
characteristic makes hydrogel polymers useful in water conservation and in solving
other environmental issues. Hydrogels help reduce water runoff and soil erosion, thus
improving the quality of lakes, streams, and rivers. Hydrogels also help with moisture
retention and water conservation by helping soil increase water holding capacity,
allowing plants to survive during droughts. Erosion control, soil management, and
environmental clean-ups are also ways hydrogels can help the environment.
Label each bag: Tap Water, Distilled Water, Salt Water. Pour 8 ounces of the
respective water into each bag. Next, place one teaspoon of water jelly crystals into
each of the bags. Observe and document what has happened in each of the bags after
5 minutes, 10 minutes, 15 minutes, 30 minutes, and one hour.
1. After doing experiment above, put all three bags into warm water and observe what
2. After doing experiment above, put all three bags into the freezer and observe what
3. Add some color to your experiments - add food coloring.
4. Hydrate some jelly crystals by putting them in room temperature water for one hour.
Then put half of them in the freezer. Use the room temperature hydrated gels and the
frozen hydrated gels and test to see what happens when you drop them into various
mediums, such as milk, cooking oil, jello, water with dish detergent added, and pop.
5. Try an experiment growing a plant cutting. Plants such as coleus, ivy, or African violet
work well. Fill 3 separate cups. One with hydrated gels, one with an equal mixture of
hydrated gels and moist potting soil, and another cup with just moist potting soil. Place a
few plant cuttings in each container and put near a light source. Observe every few days
for root growth. Which container yielded the fastest root growth? Which container
produced the most root mass?
6. Similar to Extension #5 above, use fast germinating seeds such as grass, radish, or
bean. Observe changes every few days for two weeks.
7. Take a couple of diapers and cut them open. Put them in a sealed bag and shake
vigorously. Carefully remove the diaper and stuffing, leaving the powdery substance
(hydrogel polymer) in the bag. Using a 9 ounce cup, put ½ cup of water in the cup and 1
teaspoon of the powder from the diapers. What happened after 30 seconds?! Try to
figure out how much liquid one diaper can hold.
Info from http://www.stevespanglerscience.com and from http://www.4-h.org
SD Standards for 4th grade:
Analysis, Comprehension, Applying,
Prior Preparation: Explain the effects
of erosion and drought on soil and