GGR205H1 Lecture Notes - Lecture 9: Capillary Action, Hydrogen Bond, Chemical Polarity
13 Dec 2016
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Document Summary
The movement of water up a wick typifies the phenomenon of capillarity. Two forces cause capillarity: the attraction of water for the solid (adhesion or adsorption), the surface tension of water, which is due largely to the attraction of water molecules for each other (cohesion). The discussion of the structure and properties of water in the previous section suggests three important forces affecting the energy level of soil water. First, adhesion, or the attraction of water to the soil solids (matrix), provides a matric force (responsible for adsorption and capillarity) that markedly reduces the energy state of water near particle surfaces. Second, the attraction of water to ions and other solutes results in osmotic forces and tends to reduce the energy state of water in the soil solution. The flow of liquid water in soil in all cases, water flows in response to energy gradients, with water moving from a zone of higher to one of lower water potential.
