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We Finally Know Why Oil and Water Don't Mix
CoveredTrax writes "Everyone knows oil and water don't mix. It's a simple concept, sure, but the hydrophobic interactions between fats and water are crucial to the mechanics of microbiology. The weird thing is, the base theories of chemistry suggest that there's no reason oil and water shouldn't mix, even though it's obvious that's not the case. Now there's an explanation: a team of chemical engineers at the University of California, Santa Barbara have defined an equation that measures a compound's hydrophobic character. It's the first such equation of its kind."
I thought it was to make me exercise more when trying to make my Amish bread every two weeks... the oil always takes extra long to mix in
I read TFA, and I still don't know why oil and water don't mix. Frankly, I don't think these researchers do, either. They seems to have come up with some kind of empirical formula that describes the interactions without really understanding why they are happening.
As I teach in my biochemistry class it is entropic cost of not separating them that causes their separation, but I have yet to really wrap my head around this study. Nonetheless, here are some links to the original research:
* Abstract: http://www.ncbi.nlm.nih.gov/pubmed/21896718
* PNAS (paywalled): http://www.pnas.org/content/108/38/15699
Fat is hydrophobic, ergo fat people have hydrophobia aka rabies.
If they could just solve the why water is wet we'd be good to go...
And basically it says van der Waals' theory is wrong, and here is a new equation. That's pretty much it.
Anyone who knows about this stuff want to take a look at the equation, and see if it makes any sense? Not my area.
E(D)= -2i(a-a)e^(D-D)
where:
E = energy
D = distance
a = area of molecule
Vote monkeys into Congress. They are cheaper and more trustworthy.
To research the dynamic of Salad Dressing. And im posting this sitting at work not half a mile from there.
And here I thought it was because they are more attracted to each other than they are to other types of compounds, ie water strongly hydrogen bonds to itself, squeezing out any hydrophobic molecules, while long hydrophobic chains stack strongly, squeezing out anything that doesn't stack strongly.
In high-school chem, I was taught that water molecules stick together because they are shaped like mickey-mouse heads. (The positive ears are attracted to the negative face, so they all chain together.) Oil is shaped in a straight line, with the same charge on each end, so it has no such effect. When water sticks together, it pushes the oil out, like how popular kids push the anti-social geeks out of their circles, even if they don't explicitly hate the geeks. So, did my chem teacher just make that up? Is it completely wrong?
Oil and water don't mix, you can't explain that... Oh, wait. My God's bubble of science ignorance just got smaller again.
See http://www.newscientist.com/article/dn3408-oil-and-water-do-mix-after-all.html .
I assume the new theory / equation actually works with both the water and gas molecules in consideration, although in TFA I saw no mention of it.
If you carefully put oil on top of water, you realize it "swims" as it is lighter than water.
Now if you shake it, your might expect it could "mix" with water, like alcohol e.g. does.
Now you have to understand that there are different kinds of "mixes".
Alcohol in water is a kind of solution, like salt in water (albeit looking closer at it, there is a significant difference).
However, oil in fact does mix with water pretty fine if you can make the oil into very small droplets.
Milk e.g. is an emulsion of water an oil (amoung other parts), an ordinary skin cream e.g. is a mixture of oil and water.
The main reaon why oil and water don't want to mix without help is simple: surface tension of water, and the chain building of water molecules. Water molecules are di-poles. They have a + charged and and a - charged end. Like magnets they build long chains of water molecules. That means instead of staying arbitrary close to an oil molecule they turn away from the oil and look for another water molecule. Most oils/fats have no poles.
Bottom line molecules that are bi-polar and those that are mono-polar don't mix good (or not at all).
Anyway that is school knowledge, and yes I have read the posted article ...
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
I have no background in this area, but I'm surprised to learn that we didn't know this already. Makes you wonder what other "simple" discoveries are waiting in around the corner.
XML is like violence. If it doesn't solve your problem, you're not using enough of it. --AC
I'm only remembering from High School Science, so I'm sure I'm wrong, but I thought it was as simple as polar/non-polar solvents. Since water is polar, it won't accept a nonpolar (i.e. oil) solute. Or is this just a paper about a new equation describing that relationship?
On July 31, 2009, Sterling D. Allan interviewed Paul Pantone, at the Nativo Lodge in Albuquerque, New Mexico, USA, as part of the ExtraOrdinary Technology conference. Progress report on the GEET Plasma Reactor which uses the engine exhaust flowing in one direction to heat up incoming fuel flowing in the opposite direction, around a rod of a specific length, per the type of fuel, to create a plasma gas which then performs in a very unusual way in the engine to profoundly increase the mileage of the vehicle and reduce emissions. It also enables the vehicle to run on a wide variety of fuels, including water, inasmuch as the plasma-created gas is the operating substance. ([http://www.youtube.com/watch?v=pbo80DbZHqk YouTube; Aug. 1, 2009)
source: http://peswiki.com/index.php/Directory:GEET_Reactor_by_Paul_Pantone
so while some make engine mixing oil and water some say it's impossible. Go figure!
The paper's authors haven't "explained" anything. They've devised a formula that does an acceptable job of matching empirical data. This isn't the same thing as "understanding" how the underlying competing physical processes give rise to the observed behavior of oi/water.
> the hydrophobic interactions between fats and water
> are crucial to the mechanics of microbiology
Also, salad dressing.
Dear Slashdot: next time you want to mess with the site, add a rich-text editor for comments.
I thought the winners of the 2010 Ig Nobel Chemistry prize disproved the old belief that oil and water don't mix. http://improbable.com/ig/winners/#ig2010
... what would the gulf oil spill have been like if oil and water did mix?
Dear Slashdot: next time you want to mess with the site, add a rich-text editor for comments.
OH FFS
A measure of particular phobic character does not explain why the membranes materialize.
Old news -- maybe you youngsters can't remember:
yes they do
https://app.box.com/WitthoftResume Code: https://github.com/cellocgw
That would be E(D) = -2y[sub i](a-a[sub 0])e^(-D/D[sub 0])
The OP said in his subject that now we KNOW why. No we don't!!!! We just have a couple of overpaid math geeks coming up with some algebraic gibberish that they hope nobody else will understand enough to question them. Aren't there any real scientists on this planet besides the great folks at JPL? Meaningless equations based on unfounded theories ARE NOT FREAKIN FACTS!!!!!!!!! And to the person who explained science's job as answering 'why', you are correct. However, the 'why' can't be "Because some fairies sprinkled magic dust on the oil and thats what makes it repel water". Just giving a made up answer is NOT answering the 'why'. It's no wonder this planet is going to hell on a short yellow bus. Sorry for the rant, haven't had my coffee yet today.
-- L8R, guitardood
http://www.newscientist.com/article/dn3408-oil-and-water-do-mix-after-all.html
As far as I remember, UNIQUAC is a model that can predict VLE/LLE/VLLE/whatever equilibrias by looking at the character of molecules (if it has a ketone or caboxylic acid, it will have a different character than one that is a straight chain).
And if I remember right, it does predict that oil and water will not, in fact, be in the same phase since it would then be an LLE.
However, one should always note that even though there are two phases, small amounts of water are found in the oil phase and vice versa.
a team of chemical engineers at the University of California, Santa Barbara have defined an equation that measures a compound's hydrophobic character. It's the first such equation of its kind.
Perhaps there's an escape via language lawyerism via "of its kind" but for decades there has been software to estimate the hydrophobicity of small molecules and (relying on even more approximations) proteins. Underlying that software are scores of "equations" that use tables of atomic and molecular fragment parameters of electronegativity and polarizability to calculate 'not bad' estimates of molecular hydrophobicity.
And while i'll quibble about "the first such equation"; i really think most folks should quibble over "defined an equation that measures", people armed with instruments "measure", equations 'calculate an estimate'. ok, now: hey you kids get off my lawn!
This is a really shoddy headline and article, and should never have made it to slashdot's front page.
The non-mixing of oil and water is well understood and has been for many years. You can easily find the explanation in a first year chemistry undergrad textbook.
The equation provided doesn't in fact offer an explanation and is just an empirical fit to some observed data. Without reading the paper it's hard to know what it's getting at but just from inspecting the equation it certainly isn't anything profound. For example, where is the information on the atoms constituting the molecules? (Probably in the gamma which may be surface tension, but that there's no way you can get the subtleties of hydrophobic behaviour in a single value like that.)
Grammer Nazis to the rescue!
They don't mix because there's not enough bromintation!
Just being pedantic, but homogenized milk is an emulsion; milk out of the cow most certainly separates into milk and buttercream (and the buttercream itself is a high-fat emulsion; it still has a lot of moisture in it.)
If you could explain it away with polar bonds (or lack thereof), why do emulsions emulsify? The hydrocarbon and water molecules have the same number of bonds, and the same density, no matter how vigorously you shake them.
If oil and water DID mix, the total volume of oil, which would have dispersed over the massive body of water that is the Gulf of Mexico, would have been a rounding error. There would have been some localized effects, but not catastrophic ones in any way.
I work in the field on the theory/simulation side, and have actually had dinner and discussed research with Dr. Israelachvili a couple of times. I've only had a chance to skim the paper, but I think I can summarize it pretty well... by the time I've really absorbed it you folks will have moved on to the next shiny new story so I'd better do it now!
First of all, the report claims that the paper is all about how oil and water don't mix and makes a big deal about how we don't know how that works. For simple stuff like say water and a basic hydrocarbon like octane, that's really not true... it's all about what has already been said above, polar vs. nonpolar (electrostatics) and entropy.
Things get more complicated when you want to model something like an extended hydrophobic surface, or the interactions and formation of bilayer membranes like we have in a cell. It's been known from experiments since Dr. Israelachvili's work in the 80's that if you take two such surfaces (usually mica functionalized to make it hydrophobic) and bring them together in water, they will repel each other, up until at some point they very quickly strongly attract, expel the water between them and glue themselves together (also called "cavitation"). This is the sort of data shown in Fig. 2 in the paper. The connection with membrane formation is to describe how two membranes behave when they come close together, they have to do something similar to get close enough to fuse (figure 3).
Figuring out how to describe this behaviour from a theoretical standpoint has been very difficult! We know what all the parts have to be (hydrophobic,electrostatic, steric/Van der Waals, entropic) but haven't been able to put them together in the right way to describe all of the experimental data. What Jacob and his team have done here is found a nice way to 1) describe the hydrophobic interaction between extended surfaces mathematically (the equation above), 2) combine it with all the other parts (figure 4), and 3) show that the equation with a combination of fitted and measured parameters can fit the experimental data pretty well (Table 1). It's very nice work, definitely a step forward in our knowledge of hydrophobic surface and membrane interactions, and I'm going to make sure I study it more carefully soon!
Water and oil mix. The hard part is supplying enough energy.
Hell, if I throw you hard enough, I can mix you into a wall.
...now figure out why people have the hiccups. *hic*
My blog
Huh? I thought oil and water don't mix because oils have primarily non-polar covalent bonds vs the ionic bonds in water molecules? That's what I was taught, and a quick google finds that this appears to be the generally accepted answer.
Modern copyright is theft of culture from everyone and it retards the progress of the useful arts and sciences.
The link below is a transcript from an Australian ABC network science show in 2005, Catalyst.
Professor Ric Pashley found he could make oil and water mix, and keep the result for more than a year in a sealed container without them separating, simply by getting rid of dissolved gases in the water.
He demonstrated this in his kitchen!
http://www.abc.net.au/catalyst/stories/s1314925.htm
This article http://www.anu.edu.au/CSEM/newsletters/2005/MMMar05.pdf says that by degassing water oil will mix with it.
I believe that this product http://www.squirtlube.com/products/index.php#sq06 uses the above principal to mix wax(oil) and
water.
Actually oil and water DO attract, but the water attracts water so much MORE that water attracts oil that the water separates from the oil to be with its own kind. It only LOOKS like it's trying to get away.
Don't believe me? Consider a single H20 molecule and single lipid molecule. Do they attract or repel? Attract, due to van der Waals force. Why would they repell? Therefore it has to still be true if you add a lot bunch of molecules.
Please question any "generally accepted answer",
http://tech.slashdot.org/comments.pl?sid=2466512&threshold=-1&commentsort=0&mode=thread&pid=37651492 chump, and badly. Seems you ran like a beyotch too, Lord Slimecat (or should we just call you pussy instead?).