Surface Tension Of Water

I don't beleive it would. To reduce surface tension, surfactants are used. Don't know your use for it, but if for cleaning, contact your local chemical representative.

You got me thinking about it, good for you. So I did a little more research and found these. I can't take the credit for it, but I did more research and found that it is correct.

To reduce surface tension.

1. If you increase the temperature of the liquid, surface tension of that liquid will reduce.
2. Surface Tension Can also change with the change with medium that is just above the liquid. For instance, If the medium is air the surface tension of water is 72*10^-3 N/m, but if the medium is vapor that will be 70*10^-3 N/m
3. If there is any oil or oily compounds on the free surface the liquid, then surface tension will reduce.
4. If you mix something to the liquid (a solution which would be a surfactant such as detergents) then surface tension will be changed.
5. If you electrify the liquid then ST will be reduced.

Consider that increasing temperature also increases the vibrational rate of molecules, so molecular electrostatic bonds are more strained and therefore weaker.

Pouring oil creates another layer on top of the water and oil's surface tension is about half that of water.

I enjoy questions like these, it a great refresher course as well as learning some details.

I disagree. On the surface this might seem like a good question but deep down it causes a lot of tension.

exactly

Schematic diagram of a micelle of oil in aqueous suspension, such as might occur in an emulsion of oil in water. In this example the surfactant molecules' oil-soluble tails project into the oil, while the water-soluble ends remain in contact with the water phase

no micelles of oil are produced without the presence of some surfactant molecules present that have an appropriate HLB.

firstly, then you have to take it up with these guys

and secondly, It seemed like a good reply to the humorist response

but then the surface is not water at all, and there is the interfacial tension to contend with.

Is whatever you are using to degas the water adding/leaching something to the water, such as an anionic organic molecule that is effectively a surfactant?

Are you needing the surface tension to be the same, or the real issue/problem one of foaming of the water? If foaming, there are ways to ameliorate that.

btw, welcome to CR4 and your first post.

I am thinking not. The surface tension has to do with van der Waals bonds from electrostatic charges in water molecules.

Yes, water is electrically neutral, but its charge is not symmetrical about the molecule and this causes a net dipole moment for each water molecule and a "stickiness" to water that is known as surface tension.

Molecules at the surface behave somewhat different than those in the liquid below the surface. This is due to the asymmetry of molecules at the surface. There are neighboring molecules to the sides and underneath, but none above, so the asymmetric electrostatic forces create a greater tension along the liquid surface.

Dissolved gasses are not really part of the equation. If anything, I think eliminating dissolved gasses would increase the surface tension very slightly.

I would think the attraction of a highly polar protic liquid such as water would be due mostly to hydrogen bonding, not van der Waals forces- especially with such a small molecule. van der Waals forces are more relevant to larger, especially linear molecules such as aliphatic hydrocarbons. And yes, the attraction to the liquid molecules surrounding them (as opposed to the air or higher energy vapour molecules above) develops that surface tension.

Perhaps. My recognition was that hydrogen bonding is a sub-set of van der Waals forces.

Interesting question. Reminds me of the time I tried to fix a Lava Lamp. The clear liquid part (water) had become cloudy, so I replaced it with clear water. (It did not work properly after that.)

It required the proper density of the water so that the wax would float when it heated up, but also the proper surface tension so that the wax and water would have almost (but not the same) surface tension, making the wax stream out into interesting shapes and not "ball up". I never did find the right combination of additives.

Have you slowly adjusted the salt I'm the water, with pickling salt?

This was many years ago. I recall adding salt to increase the water density and a bit of detergent to change the surface tension. It was an interesting experiment, but I finally gave it up and never did get a good result.

The water in the lava lamp is a brine that using of all thing pickling salts. There is a Web site strictly for making your own homemade lamp. The wax is pretty interesting also to make.

Interesting! Water is covalently bonded with its molecules and stable, means it does not react to oxygen and carbon dioxide.-(correct if im wrong,) Oxygen and Carbon dioxide in water is a form of solution. Dissolved Oxygen, dissolved Carbon dioxide in terminology. With it in water, it should not affect intermolecular binding of water. If it does, it should have affected already the surface tension of water everywhere, since boundary of air and water is at the surface. This is good to be true unless rebut. ;)

Soda has a low pH, so CO2 must dissociate forming H2CO3 (carbonic acid).

pH of soda:

http://fit4maui.com/water/pu/soda_ph.html

It should be simple to compare the surface tension of water and soda by seeing how far up a straw the liquid rises.

Exactly, i was not careful about it, almost water or moisture is avoided on equipment- since its almost always a component or reactant to form acid by-products, but it would have been different if starch is indeed mixed with water even no chemical reaction or new compound was formed, would you agree Rix?

I don't know what starch (cornstarch?) does to the surface tension, but it does some wild and crazy things to the viscosity.

http://en.wikipedia.org/wiki/Non-Newtonian_fluid

A non-Newtonian fluid

Noudge: while you are at it, Google this: "New Super-hydrophobic surface preparation of metals using lasers" if you want to really see a watershed moment. Pardon any resemblence to a pun.

I think Phoenix and AH have answered your basic question.

Can you elaborate on the "in a closes loop" part of the question.

Thank you all for your help.

UK - Closes should read closed loop - The water in the pipes of a central heating system.
The question could be: If we remove air, dissolved oxygen and other gases from the water in the pipes will we have lass surface tension.
Will the water slip through the pipes better?

No- at least not to any practically measureable extent. That is affected far more by the VISCOSITY of water rather than by surface tension. Note that in most closed systems such as boilers (and also fire suppression systems that aren't actually spraying) dissolved gases are quite low anyways, either by design of chemical additives or natural leaching/ oxidation with time.

Water in most closed loop systems will lose most of the dissolved gases, especially when this is a hot closed loop, and a good tight system (without leaks). The water will also tend to soften itself, since the water will become more alkaline over time, hardness ions will scale a thin scale inside pipes, that is so thin almost to be unnoticed. The same cannot be said for a badly designed hot water closed loop where make up water is consistently needing to be added dur to leakage. In such a system, corrosion issues take over, and the pipes lose their smooth profile.

The tight system works well, pipes stay smooth, water softens, and instead of surface tension, you might should look at viscosity (drag) that robs energy from any pumped system. Look at any filters in line to make sure these are being changed out on PM schedule, as this is another zone where pumping energy losses take place.

Most central hot water loop systems will not perform as well a few years down the road as from new due to poor maintenance of the water chemistry. There is more than one treatment scheme for such loops. One utilizes nitrate/nitrite, another uses phosphate/molybdate, while another one uses soft water with added sodium metasilicate. It all depends on the system integrity.

James Thank you.

You said:

''The water will also tend to soften itself, since the water will become more alkaline over time, hardness ions will scale a thin scale inside pipes, that is so thin almost to be unnoticed''.

So in a hypothetical case if we are able to take out almost all the gasses in the water and the system has no air entering then the water will be soft.

So soft water appears to have a greater slipperiness than hard water so I think soft water will flow quicker through the pipes than hard water. What do you think.

Most of the time, there is no need to pump out the soluble gases, unless there are wide temperature swings, and some sort of point in the system where air and water can come to equilibrium. Most of the time, these closed hot loop systems become anaerobic all by themselves, simply because the gases are no longer soluble at high temperature, what little corrosion that does take place helps to scavenge the oxygen, and this is partly what raises the pH in these systems. Once the pH is in the right range, corrosion reaches its lowest rate for the given type of corrosion inhibition scheme in place.

I tend to agree that soft water may in fact end up with a slightly lower drag, although in most cases the limiting factor is simply the cleanliness of the pipes.

OP?

OP: Original Poster, the one who asked the question or started the discussion.

Answer to your (OP) question with reference to your later condition of this being a hot water closed loop: Not enough for it to make any appreciable difference in operation of the system.

For engineering purposes you should be thinking viscous drag, and you will not change water's viscosity enough for that to matter either, but what you do need to look for is signs of corrosion in the piping that result in increased pumping energy losses due to the increased surface roughness of the pipes.

Dear James thank you for your reply. Tweed London UK

Re: You said

''For engineering purposes you should be thinking viscous drag, and you will not change water's viscosity enough for that to matter either, but what you do need to look for is signs of corrosion in the piping that result in increased pumping energy losses due to the increased surface roughness of the pipes.''

If we could achieved air, oxygen and nitrogen and other gas levels down to parts per million in the water in the pipes I do not believe there should be any corrosion within the system or increases surface roughness of the pipes.

What do you think?

Of course traditional corrosion requires oxygen for the corrosion cathodic reaction to take place, and pretty much requires oxygen for the cathodic reaction of a galvanic coupling to corrode the less noble. Thus, if you consistently maintain or maintained a system free of dissolved gases, then yes, corrosion should be minimal. However, leaks from the system that result in a make up water requirement will in fact supply all the necessary oxygen.

You can verify the state of the system during an outage can you not?

Having baffled you with all my BS, now I will prove to be a blithering idiot and state that lower surface tension may actually help with boundary layer effects, it all depends on how narrow the pipes are, the Reynolds number of flow, etc.

One final time: As long as the loop is considered to be "tight", meaning little to no water losses, then corrosion will assume a low value, as the minimal corrosion reaction that will take place produces hydroxide at the local cathodes, causing system pH to shift upward, and also throttling the corrosion tendency down to as low as it can be for the pH at that time. This is why all the other worrying with attempting to remove gases will not gain particularly anything pertinent to the longevity of the system, and in fact could play a significant detriment to the cost of the system, its maintenance, and could introduce problems that are not desired in the long run. Experience has already shown this in many, many installations around the world. Just about the best loop involves no leaks, possibly takes advantage of magnetically coupled pumps.