Use candy to teach young children that a solid can grow bigger by absorbing liquid. Place two gummy bears in separate, clear containers. Fill one container with water, and keep the second bear dry. Keep a watch on the bears for several hours. When the submersed bear is visibly bigger, discuss with your child why this happened. You can also try this experiment with raisins, but let them soak overnight.
A second experiment demonstrates that seeds must take in water in order to grow into plants. Plant two beans in separate pots with dry soil. Water one for several days, and leave the other dry. When the watered bean sprouts, discuss how the seed absorbed water from the soil.
Ask children to test what kind of paper or cloth is the best to use to mop up a spill. Allow kids to feel, tear and scrunch different types of paper and cloth. Hang a small piece of each type over a container filled with colored water. Watch to see which material absorbs the most liquid.
Older kids love to turn drinking straw wrappers into worms. Have students fold straw wrappers into accordion shapes. Use the straw to slowly drip small drops of water onto the worm-shaped wrapper. Discuss why the wrapper grows when it gets wet.
We know that hydro gel crystals like the kind used in disposable diapers can absorb about 500 times their own weight in water, but do these super soakers also absorb other liquids? Experiment with different types of liquid.
Older students can investigate the absorbency of different fabrics by recording the time it takes for them to dry. Use equal-sized samples of silk, cotton, polyester blends and terry cloth, and record how long it takes them to dry on an outdoor clothesline. For a fun project that will get their hands dirty, older kids can test which fabrics best absorb dye. They’ll learn a thing or two about absorption and also come away with some artistic, tie-dye T-shirts.