Capillary action at the molecular level
November 8th 2010 05:20
Water is composed of 2 Hydrogen atoms and 1 Oxygen atom. The Hydrogen atoms are positioned together on one side of the Oxygen atom and have a positive charge on each. The Oxygen has a negative charge. This is polarity. Glass is Silicon surrounded by Hydrogen atoms. Each Hydrogen has a positive charge. So, in a glass capillary tube, the Oxygen in water is attracted to the Hydrogen in the glass. This is electrostatic attraction or adhesion. The force of gravity pushes down on the body of water and inside the tube, the adhesion (electrostatic attraction) reduces the effect of gravity so water rises in the tube.
If you were to bend the top of the capillary tube over, gravity would attempt to pull water back into the pool of water. However, the mass of water is too small and adhesion of water to the tube is stronger than gravity.
Now. What if you were to arrange 20-30 capillary tubes together so the meniscus' touch at the end of each tube? Hydrogen bonding is stronger than electrostatic attraction (adhesion), so when water in each tube touches, water re-coheres and forms a droplet large enough that gravity can overcome the adhesion to the tubes.
This is due to the intermolecular force differential. Hydrogen bonding > electrostatic charge. And then gravity acting on mass.
The interplay of these 3 forces (properly engineered) results in nearly perpetual motion.
If you were to bend the top of the capillary tube over, gravity would attempt to pull water back into the pool of water. However, the mass of water is too small and adhesion of water to the tube is stronger than gravity.
Now. What if you were to arrange 20-30 capillary tubes together so the meniscus' touch at the end of each tube? Hydrogen bonding is stronger than electrostatic attraction (adhesion), so when water in each tube touches, water re-coheres and forms a droplet large enough that gravity can overcome the adhesion to the tubes.
This is due to the intermolecular force differential. Hydrogen bonding > electrostatic charge. And then gravity acting on mass.
The interplay of these 3 forces (properly engineered) results in nearly perpetual motion.
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