Water surface tension

[ascalon]

Hello all :) . Any knowledge appreciated.

 

What exactly determines the surafce tension and effectiveness of cappillary action in water? How can the surface tension of water be lowered? Are there any sort of devices (products or do it yourself) that can achieve this?

 

I ask these questions because I have seen that a lower surface tension in water would seem to enhance the capillary action in plants, because of cohesion/adhesion properties. I grow plants, and have studied water for some time, and have realised that hydration is key to growth. It's a simple hop and a skip to make the conclusion between low surface tension and increased hydration, it's very factual. My main concern is in figuring out how to lower the surafce tension of the water, though I think I may have found a good product, meant for reducing scale in pipes, though they say it also does this through lowering the water's surface tension. Thanks for any help :) .

[cwes99_03]

Surface tension is a product of the chemical. Water (being a chemical made up of 2 parts hydrogen and 1 part oxygen) has different values of surface tension at different temperatures. Temperature affects surface tension because suface tension is determined by at least two things. 1) intermolecular bonding (hydrogen bonding, van der waal's forces and 2) intermolecular spacing. Both are affected by temperature.

[DFINITLYDISTRUBD]

I've heard (key word heard) that glycerine lowers waters surface tension.

 

don't know if this helps or not...hope it does.

[cwes99_03]

Adding dish soap will lower the surface tension of a pool of water. Adding glycerine I believe increases the surface tension of a pool of water. However, it is no longer water, but a mixture of water and something else.

 

That being said, putting certain fertilizers in water may reduce its surface tension.

[ascalon]

Thanks.

 

True that temperature and chemicals can effect surface tension, but it's also the arrangement of the water molecules too, isn't it? I'd be looking for physical (not chemical or temperature) methods of changing that. From what I know, pure water and distilled water have very low surface tensions, and are largely pure H2O. However, I have heard also that plant fluids would have a low surface tension of about 40 dynes/cm, and possibly other natural "organic" fluids may have similar values of surface tension. Tap water, would usualy be about 80 dynes or higher.

 

Also, in some studies related to global warming and atmospheric conditions, it's shown that there is a relationship between the enrgy given off by the light of the sun, which is absorbed by water DEPENDING on its vibration, state, and structure. The variablity in the properties of water means it has the ability to absorb wide spectrum of energy in the electromagnetic spectrum (mostly in the longer wavelengths). Anyway, my point is there are different influences that can effect water down to the molecular level.

[DFINITLYDISTRUBD]

I'd be looking for physical (not chemical or temperature) methods of changing that.

 

Placing it (the water) into a chamber and drawing a vacuum would reduce surface tension. (or convert it to a gassious state dependant on - pressure )

[cwes99_03]

Hmm reducing surface tension by reducing pressure. Yah that should work the same way increasing the temperature of the water would work. Look up some zero g plant experiments to see how they deal with it.

 

Otherwise...

I'd be looking for physical (not chemical or temperature) methods of changing that.

Temperature variation is a physical method. It is also about the only non-chemical way of changing surface tension. The other one I can think of off the top of my head would be to use some sort of harmonic vibration to set up a standing wave on the surface of the liquid, this would increase the total surface area of the water and I would have to imagine reduce (or maybe even increase) surface tension.

I read a book once when trying to learn about capillary waves and water tension when doing a 5 day experiment on wave velocity and packet velocity during my May term experimental physics class. Had to derive a bunch of calculations and whatnot. Sorry, I don't have my lab notes as they stayed with the lab so I can't tell you much.

 

The difference between distilled and pure water is little or none. The thing you will want to be aware of it deionized-distilled vs. non-deionized distilled water. Distilled means that heavier elements (anything but H+ and OH-) has been removed, usually through evaporation. Deionized means that there should be very little extra H+ or OH- ions left over (thus making it perfectly neutral pH.) Is that right fellas? Just going off of memory.

[moo]

Are there any sort of devices (products or do it yourself) that can achieve this?

Yes, there are quite a few commercial surfactants on the market.

It's a simple hop and a skip to make the conclusion between low surface tension and increased hydration, it's very factual.

You are correct. Commercial surfactants are designed to make water "wetter" (less surface tension), and many are specifically designed to be used with crop/pasture sprays (herbicides etc.) so the plant will absorb a larger percentage of the solution, which results in reduction of both volume needed and wasted runoff.

 

Mild soap (as mentioned) is actually used for this purpose occasionally, but its tendency to foam and leave residue in the spray equipment makes it less desirable (although it is considerably cheaper). :D

 

moo

[cwes99_03]

Of course the issue with these surfactants is that some also may prove to be harmful to the plant itself or to the being who masticates and digests such a plant.

[moo]

Of course the issue with these surfactants is that some also may prove to be harmful to the plant itself or to the being who masticates and digests such a plant.

No argument here, but the same issue could be raised with irrigation water from many lakes and streams. :)

 

moo