What is Capillary Action?

Capillary action is a well documented phenomenon where a liquid will rise in a capillary to an equilibrium position that is a balance between the adhesive forces of the surface tension of water and the force of gravity that is acting on the elevated liquid. Capillary action is what causes water to rise up from the water table through a porous cinder block or cement wall, creating excessive dampness and moisture. This can be readily seen by placing a dry sponge on a plate of water. Water will rise through the microscopic pores of the sponge and cause the entire sponge to become wet. (This is also the reason why adding soil to a wet area will not make it dry.)

Why does water expand when it freezes?

According to Dr. Arnold G. Gill (Astrophysician, Malaspina University-College, British Columbia, Canada),: "The expansion has to do with the peculiar molecular structure of water. Within the limits imposed by this keyboard, a water molecule looks like (Left diagram). Each of the hydrogen atoms weakly attracts nearby oxygen atoms, so water binds together. When liquid, the binding is weak, but when solid, the bonds become quite strong, and constrain how the molecules may arrange themselves as a crystal. In its liquid state, the molecules are free to roam around wherever they wish. However, in its frozen state, the water molecules form a hexagon (six-sided figure), giving the beautiful six-sided snowflakes that we are all familiar with. In this state, the molecules line up approximately like the sketch (right diagram) below with the lines showing the molecular bonds holding the molecules in place. Notice that the center is empty! In its liquid form, with the molecules moving about freely, you will find an H2O molecule in the center of such a structure, but not in its solid state. So, a given amount of water will use up more room as ice than as a liquid, because of the empty space that appears as it freezes. Thus, ice is less dense and it floats. (And in case you are wondering, the center is EMPTY; it is NOT filled with air. Air bubbles are extra effects that help to float ice, but air bubbles are not needed to get ice to float.) You've probably heard that 90% of an iceberg is under water. This suggests that the density of ice is about 10% (1/10) less than that of water. Yet, from the simple diagram above, there are 6 water molecules where before there were 7 - a difference of about 14% (1/7). Why the discrepancy? While frozen water has a unique crystal structure, it also acts like every other substance in the world - it contracts when it cools. That is, the average distance between adjacent water molecules still decreases when water freezes (in the diagram, the lines connecting the molecules get shorter). The net result is that the group of molecules shrinks, but the center remains empty - or 1/7 shrinks to about 1/10."

Groundwater levels may have a long term trend of rising or falling

Water will flow faster in a pipe that is about 80 percent capacity than it will in one that is near 100% capacity under gravity flow.

Water speed in a pipe will vary with the texture of the pipe, diameter, slope, and material.

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