Sodium polyacrylate is a hydrophilic (water loving) polymer. When dry, the polymer is tightly coiled together. When water is added, the polymer begins to unfold, forming a complex with the water. As more water is added, the polymer uncoils more. When salt is added, some of the water is attracted to the salt, making salt water. Then the polymer collapses back into the coil.
Sodium polyacrylate is used in many applications. A common one is diapers. In addition, it is used as a soil additive to hold water for long periods for plants.
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