How does desiccant absorb and hold water? — JP, Houston, TX
Water molecules from the air are continuously colliding with surfaces and sometimes one of those water molecules will stay attached to a surface for some amount of time. That water molecule forms a weak chemical bond with the surface and remains there until thermal energy knocks it back into the air. As a result of this occasional sticking, most surfaces have a thin layer of water molecules on them. Desiccants are materials that tend to keep those water molecules for a relatively long time and that have lots of surface area on which those water molecules can stick. However, the strongest desiccants react chemically with water molecules so that those water molecules essentially never leave.