What causes liquid to rise in a capillary tube?

In summary, the energy that causes the liquid to rise in a capillary tube comes from surface tension, not air pressure, as originally thought. This can be seen through the contact angle, which determines whether the surface is hydrophobic or hydrophilic, and ultimately affects the liquid's ability to rise in the tube. This is also how damp-proofing injections work, by lining the capillaries with a hydrophobic material to prevent rising damp.
  • #1
AudioFlux
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This question struck me when i was watching a liquid rise in a capillary tube. I'm curious to know from where the energy gets transferred to the liquid to rise above the surface. Well, one possible explanation that i can think of is air pressure. Though, it can be a possible reason only if the other end is closed (i don't remember if it was open or closed). So am i on the right track?
 
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  • #2
Hi AudioFlux! :smile:
AudioFlux said:
I'm curious to know from where the energy gets transferred to the liquid to rise above the surface. Well, one possible explanation that i can think of is air pressure.

No, it's surface tension, see …

http://en.wikipedia.org/wiki/Capillary_action#Height_of_a_meniscus
http://en.wikipedia.org/wiki/Wetting
http://en.wikipedia.org/wiki/Contact_angle :wink:

(if the contact angle is greater than 90°, the solid surface is hydrophobic, and the liquid will fall

this is how those damp-proofing injections work, they line the capillaries in the bricks with a hydrophobic lining)
 
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1. What is capillary action?

Capillary action is the movement of a liquid through a narrow space or tube without the assistance of external forces such as gravity. It is caused by the cohesive and adhesive forces between the liquid molecules and the walls of the tube or space.

2. How is work done in capillary action?

Work is done in capillary action when the liquid moves against the force of gravity or any other external resistance. This work is done by the surface tension of the liquid, which is the result of the cohesive forces between the molecules of the liquid.

3. What factors affect the amount of work done in capillary action?

The amount of work done in capillary action is affected by several factors, including the surface tension of the liquid, the diameter of the capillary tube or space, and the angle of contact between the liquid and the walls of the tube or space. The height to which the liquid rises is also a factor in determining the work done.

4. How does capillary action contribute to plant growth?

Capillary action plays a crucial role in plant growth by allowing water and nutrients to be transported from the roots to the leaves through the capillary tubes in the plant's vascular system. This process is essential for maintaining the plant's structure, as well as for photosynthesis and other metabolic processes.

5. What are some real-life applications of capillary action?

Capillary action has many practical applications in everyday life, such as in paper towels, which use capillary action to absorb and hold liquids. It also plays a vital role in the functioning of inkjet printers and medical devices, such as capillary tubes used for blood testing. Capillary action is also used in the design of some irrigation systems and in the transportation of water in trees and other plants.

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