Surface of a liquid behaving like a stretched membrane

In summary, the question is whether the surface of a liquid behaves like a stretched membrane due to surface tension or all the forces acting on the liquid molecule at the surface. It is suggested that if the surface is stretched due to surface tension, then the forces causing the stretching are only horizontal. However, if the surface is stretched due to all forces, including those pulling into the bulk of the liquid, it is difficult to imagine how a bubble membrane could remain stretched without bursting. It is then clarified that surface tension supports the object by aligning along the tangent to the curve of the depression made by the object.
  • #1
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The surface of any liquid behave like a stretched membrane. Is it because of surface tension or all the possible forces acting on a liquid molecule at the surface? I asked this question because if the furface behaves stretched because of surface tension then it means that the forces making the surface stretched are only horizontal. Whereas if the surface if behaving like a stretched membrane because of all the forces on the molecule on the surface this means the forces going into the bulk of the liquid also make it stretched. I just can't imagine the latter situation as in if we have a streched bubble membrane. It is stretched because of all the horizontal forces appears good rather than stretched because of all forces because if all the forces pull it, won't the bubble membrane burst as there would be an excess downward force?( Since there is a net force on the molecule at the top of the membrane which tries to bring the molecule at the top into the bulk.) But since the bubble membrane doesn't burst it means that it gets stretched only by the horizontal forces?
 
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  • #2
andyrk said:
... if the furface behaves stretched because of surface tension then it means that the forces making the surface stretched are only horizontal

Why? That would mean that INSTANTLY when the surface is deformed away from horizontal, the surface tension would no longer support whatever it is supporting. Doesn't seem to make sense.
 
  • #3
phinds said:
Why? That would mean that INSTANTLY when the surface is deformed away from horizontal, the surface tension would no longer support whatever it is supporting. Doesn't seem to make sense.

When surface is deformed then surface tension would be along the tangent to the curve(shape of depression which the object made). So it would be able to support the object. Besides its nowhere written that surface tension supports the body in consideration. Is it?
 
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  • #4
andyrk said:
When surface is deformed then surface tension would be along the tangent to the curve.
Yes. This is a correct assessment. In the case of a bubble, there are two surfaces (inside and outside of the bubble thickness), so you have to take into account the surface tension at each surface.
 
  • #5


I can provide some insight into this question. The surface tension of a liquid is indeed a key factor in causing the surface to behave like a stretched membrane. Surface tension is the result of the cohesive forces between liquid molecules, which create a tension or “skin” on the surface of the liquid. This tension pulls the surface molecules inward, creating a stretched surface.

However, it is important to note that other forces, such as gravity and pressure, also play a role in the behavior of the liquid surface. These forces act on the liquid molecules not just at the surface, but also throughout the bulk of the liquid. This means that the surface tension is not the only force acting on the surface molecules.

In the case of a stretched bubble membrane, the surface tension is indeed the dominant force that keeps the bubble from bursting. The cohesive forces between the liquid molecules are strong enough to withstand the external forces acting on the bubble, such as gravity and pressure.

It is also worth noting that the stretched surface of a liquid is not a perfect analogy to a stretched membrane. The behavior of a liquid surface is more complex, as it is constantly changing and adapting to its surroundings. The surface tension is just one factor that contributes to this behavior.

In conclusion, while surface tension is a key factor in causing the surface of a liquid to behave like a stretched membrane, it is not the only force at play. Other forces, such as gravity and pressure, also contribute to the overall behavior of the liquid surface.
 

1. How does the surface of a liquid behave like a stretched membrane?

The surface of a liquid behaves like a stretched membrane because the molecules in a liquid are constantly moving and colliding with each other, creating a cohesive force that pulls the surface of the liquid tight, similar to a stretched membrane.

2. What causes the surface tension of a liquid?

Surface tension is caused by the cohesive forces between the molecules in a liquid. These forces create a strong bond between the molecules, allowing the surface of the liquid to resist external forces and behave like a stretched membrane.

3. How is surface tension measured?

Surface tension is measured by the amount of force required to break the surface of a liquid. This can be done by using a device called a tensiometer, which measures the force needed to separate two plates from a liquid surface.

4. How does surface tension affect the behavior of insects on water?

Surface tension allows insects to walk on the surface of water without sinking. The cohesive forces between the water molecules create a strong enough surface tension to support the weight of small insects, such as water striders.

5. What are some practical applications of surface tension?

Surface tension has many practical applications, including in the creation of soap bubbles, the functioning of capillary tubes in plants and trees, and the formation of droplets and bubbles in various industrial processes. It also plays a role in the functioning of lungs and alveoli in the human body.

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