Difference between Capillary Rise and Capillary Depression

In summary, The difference between wetting angle and capillary rise method for surface tension is that wetting angle is a measure of how a liquid interacts with the surrounding gas and capillary walls, while capillary rise method is a physical and mathematical description of how a liquid behaves on a surface. The wetting angle can vary depending on the strength of these interactions, but the concept applies to all liquids on all surfaces.
  • #1
Saterial
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As the title states, can anyone help me understand what the difference between the two is? I've been trying to look everywhere but nothing really explains why they're different. I just thought it would be the same.

This is based on the capillary rise method for surface tension.
 
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  • #2
Do you know what the wetting angle is and how it depends on the interactions between liquid, surrounding gas and capillary walls?
 
  • #3
I do yes, mercury has an angle greater than 90 degrees unlike other solutions. But this only applies to mercury does it not?
 
  • #4
No, it applies to all liquids on all surfaces. Depending on which interactions are stronger liquid either "prefers" to sit as a spherical droplet or to spread away on the surface - in both cases it tries to find the minimum energy form. Physical/mathematical description is always the same.
 
  • #5


Capillary rise and capillary depression are two different phenomena that occur due to the surface tension of a liquid. While they both involve the movement of a liquid in a narrow space, they are caused by different factors and have different effects.

Capillary rise is the upward movement of a liquid in a narrow tube or capillary due to the cohesive forces between the liquid molecules. This phenomenon is commonly observed in a glass capillary tube, where the liquid rises to a height that is inversely proportional to the radius of the tube. This is because the smaller the radius, the greater the surface tension force acting on the liquid, causing it to rise higher.

On the other hand, capillary depression occurs when a liquid is placed in a narrow space, such as between two closely spaced plates. In this case, the liquid is pulled downwards due to the adhesive forces between the liquid and the solid surfaces. This results in a concave meniscus, where the liquid appears to be depressed in the middle.

In summary, capillary rise and capillary depression are two distinct phenomena caused by different forces. Capillary rise is due to cohesive forces between liquid molecules, while capillary depression is caused by adhesive forces between the liquid and solid surfaces. Understanding the difference between these two phenomena is important in various scientific fields, such as fluid mechanics and surface chemistry.
 

1. What is capillary rise?

Capillary rise is the phenomenon of liquid moving upwards through a narrow tube or porous material, against the force of gravity, due to the adhesive and cohesive forces between the liquid molecules and the tube or material.

2. What is capillary depression?

Capillary depression is the opposite of capillary rise, where liquid moves downwards through a narrow tube or porous material, due to the cohesive forces between the liquid molecules and the tube or material being stronger than the adhesive forces.

3. What is the main difference between capillary rise and capillary depression?

The main difference between capillary rise and capillary depression is the direction of liquid movement. Capillary rise involves liquid moving upwards against the force of gravity, while capillary depression involves liquid moving downwards due to the cohesive forces between the liquid and the tube or material.

4. How does surface tension play a role in capillary rise and capillary depression?

Surface tension, which is the force that causes the surface of a liquid to contract, plays a major role in both capillary rise and capillary depression. In capillary rise, surface tension helps to pull the liquid upwards against gravity, while in capillary depression, it helps to pull the liquid downwards.

5. What factors can affect the height of capillary rise or depression?

The height of capillary rise or depression can be affected by several factors, including the surface tension of the liquid, the diameter of the tube or pores, the density and viscosity of the liquid, and the type of material the liquid is interacting with. Temperature and atmospheric pressure can also have an impact on the height of capillary rise or depression.

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