Question

Why dose water rise up a blotting paper?

Answer 1

Capillarity, or capillary action, occurs when intermolecular bonding between water molecules and molecules of another material is greater than the intermolecular bonding among water molecules themselves. This is called adhesion, and when it happens water will tend to spread over the surfaces of the other material, even climbing against gravity to do so. Cohesion among the water molecules will drag along those water molecules not in direct contact with the material, and surface tension will hold the water together as it adheres to the surface. Adhesion may be strong enough to raise the water against gravity. If a material is porous enough, the water can continue to climb for quite a distance. But on a smooth non-porous surface, the water will stop climbing when the weight of the cohered water is greater than the adhesion can support.