Adhesive water

[SaintJude]

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View attachment 18628

Edit: Answer is A?! Oh Examcrackers...

 

[chiddler]

I think it's the same. Capillary action occurs because of water in a small enough diameter tube of some sort, not because of weaker/stronger hydrogen bonding.

 

[milski]

I think it's the same. Capillary action occurs because of water in a small enough diameter tube of some sort, not because of weaker/stronger hydrogen bonding.

Capillary action occurs because of strong attraction between the molecules of the liquid and the molecules of the wall of the container. I'm tempted to say D - stronger attraction to the walls will just make for steeper edge of the liquid meniscus but the effect should be observable in any case when there is strong enough attraction with the container.

 

[chiddler]

Capillary action occurs because of strong attraction between the molecules of the liquid and the molecules of the wall of the container. I'm tempted to say D - stronger attraction to the walls will just make for steeper edge of the liquid meniscus but the effect should be observable in any case when there is strong enough attraction with the container.

you're right. but that's where small diameter comes in. when diameter is small enough, the "meniscus" formation causes the upward movement. if diameter increases, then a real meniscus forms and no capillary action happens.

but it seems the answer is A. why wouldn't it be C?

 

[milski]

you're right. but that's where small diameter comes in. when diameter is small enough, the "meniscus" formation causes the upward movement. if diameter increases, then a real meniscus forms and no capillary action happens.

but it seems the answer is A. why wouldn't it be C?

There is always a meniscus. The movement up stops when the weight of the liquid raised is equal the force pulling it up. Since the weight decreases as r^2 (cylinder volume) but the force only as r (the circumference of the tube/container) the height of how much the liquid is raised increases as the radius decreases.

I have no good explanation why it would be A/B/C - I don't see how the difference in this forces comes into play.

 

[SaintJude]

I think that the answer relied upon understanding that "water rising" meant that an upward force, due to capillary action, was acting on the liquid water. The forces between the water and the walls, (the soil in this case) will cause this upward force on the liquid.

Looked to Hyprphysics: Capillary action occurs when the adhesion to the walls is stronger than the cohesive forces between the liquid molecules, the liquid will rise. So, if force is upward due to capillary action occurs it's because adhesion > cohesion. So answer is A.

And since I'm not sure if I explained that well (& since this is my own question, and I may be too confused)--Here is the reference:

http://hyperphysics.phy-astr.gsu.edu/hbase/surten2.html#c4

 

[chiddler]

I think that the answer relied upon understanding that "water rising" meant that an upward force, due to capillary action, was acting on the liquid water. The forces between the water and the walls, (the soil in this case) will cause this upward force on the liquid.

Looked to Hyprphysics: Capillary action occurs when the adhesion to the walls is stronger than the cohesive forces between the liquid molecules . So, if ever capillary action occurs it's because adhesion > cohesion. So answer is A.

oh yeah! seems obvious now that you write it out.

thanks.

 

[MedPR]

Answer A seems obvious to me based on the fact that water has a meniscus due to it "climbing" up whatever container you put it in. But if that's improper reasoning, then I have no clue 🙁

 

[ljc]

Answer A seems obvious to me based on the fact that water has a meniscus due to it "climbing" up whatever container you put it in. But if that's improper reasoning, then I have no clue 🙁

This is fine reasoning. Basically all you need to know for capillary/meniscus problems is:
If intermolecular forces > molecular to surface forces, the meniscus is convex and will lower.
If intermolecular forces < molecular to surface forces, the meniscus is concave and will rise (as in this question).