If the second law of thermodynamics states: >Entropy must

>>8882676
which am i explaining?
that oil floats in water or that oil doesn't mix with the water?

Things at "equilibrium" have higher entropy

>>8882686
>>8882687
they don't and wont mix therefore entropy isn't increasing therefore thermodynamics is bullshit

>>8882688
You have a flawed and naive definition of entropy.

>>8882688
it's not energetically favorable for the less dense, non-polar oil to mix with the polar water.

>>8882676
>Entropy must always increase or not change in a closed system
ftfy

>>8882688
>implying it doesnt take outside forces thus outside energy for the local entropy to decrease.
overall entropy must always be increasing but in a closed system you can temporarily decrease it. Like what the fuck do you think a fridge does?

>>8882676
The second law isn't "entropy always increases", it's really "entropy never decreases". There's a subtle difference.

>>8882735

The total entropy of the universe always increases, but on a small scale you can decrease the entropy of something, but in doing so you create more entropy around it

>>8882676
>Entropy must always increase in a closed system
a) That's not a closed system, the top is open and the sides conduct heat.

b) 2nd Law only says Entropy cannot decrease in a closed system--it can still remain constant

c) When an initially mixed emulsion of oil in water separates into layers, it releases heat, raising the system's temperature. The higher temperature allows more energy states to be occupied (variations in amounts of movement of particles), more than compensating for the increased order due to the separation of the layers.

>>8882771
This is factually incorrect. please go read what the second law actually says. In a closed system entropy can be decreased. The reason OP's pic happens is because of outside forces(gravity) acting on it decreasing the overall entropy in the closed system at the cost of it giving off heat

>>8882779
>In a closed system entropy can be decreased.

No. No, it really can't. At best, entropy of one part can be reduced by increasing entropy in another part by an equal or greater amount.

>The reason OP's pic happens is because of outside forces(gravity) acting on it decreasing the overall entropy in the closed system at the cost of it giving off heat

If outside forces mediate exchange of mass or energy with outside particles, the system is not closed.

The phase separation occurs due to the electromagnetic force (hydrophobic vs. hydrophilic molecules). The same phase separation would occur in zero-G (except the effect would be spherically symmetric). Gravity affects the shape but is negligible with regard to the thermodynamics.

>>8882688
Hard to follow without your definition of entropy.

>>8882802
No fucking shit sherlock. Fine lets take it at face value and say there are never any closed systems ever due to the forces of gravity and flux of space in vaccum. Congratz on the pedantic definitions.

And youre wrong about the electromagnetic force being the cause. Look up how they filter water to reuse it in space. They wont seperate out if gravity is not acting on it.

>>8882810
Um, I think we're arguing past each other. Here is what I think you're suggesting:

>Oil is less dense than water.
>Anything less dense than water will separate into a layer on top of water when put into a glass subject to gravity, instead of remaining mixed.
>Therefore oil forms a layer on top of water.

I agree with the first premise and with the conclusion, but I disagree with the second premise. Ethanol, for example, is less dense than water--indeed less dense than oil--yet it remains mixed with water when placed in a glass, gravity be damned.

This implies that gravity cannot be a *sufficient* condition to explain the separation of oil and water into layers.

I suggest instead that the separation occurs due to electromagnetic forces: oil-oil interactions and water-water interactions are more energetically favorable, collectively, than oil-water interactions. So separation into layers is energetically favorable, and should occur even in negligible gravity.

Water and ethanol, on the other hand, do not separate into layers because the two are miscible, and this miscibility is due to the hydrogen bonds between them (which oil cannot form). These bonds make remaining a solution more energetically favorable than otherwise, so they stay mixed, even when exposed to gravity.

>>8882860
lol i know what the polarity of molecules means.
If you put a homogenous mixture of polar and non polar molecules here on earth they would separate out. If you did this in space they would not do this naturally. This is why they have to centrifuge out oils on space.

>>8882688
The second law of thermodynamics says nothing about the increase rate of entropy.
The water and the oil are actually slowly reacting with one another at their interface, it's just that it takes a very long time.

>>8882864
Ah, I think I see where the confusion lies. I agree that in space, oil and water won't necessarily separate *well.* For example, the oil will end up as millions of little suspended droplets within a larger blob of water, and the droplets may take an extremely long time to merge.

The result is that the oil and water are separated on microscopic scales, but may be very mixed on macroscopic scales, because gravity is missing. The gravity would provide a macroscopic ordering (separation by density) that is insufficient to prevent favorable mixing (ethanol/water) but sufficient to impose a visible separation into layers when there is *already* separation on the scale of tiny droplets due to electromagnetic forces.

Based on some of the answers in this thread, I'm pretty convinced people be trollin.

>>8882883
Ah we were talking about different affects. I wasnt talking about the individual heat causing the gradual combining of larger droplets due to the electromagnetism of the polar molecules. I was only reffering to the macro effect we see in Op's picture of total separation.
What law/equation could be used to determine the time it takes for the larger droplets in zero gravity? i cant remember ever reading/doing homework on anything of the sort.

>>8882895
Happy to have reached agreement.

I think the relevant equations would be governed by surface effects. In the absence of a surfactant, I assume that there would be a gain from decreasing the total oil/water surface area as a result of joining oil blobs. But it might be a small effect, and could take a while.

The kinetics would be governed by the energy gain for merging (which helps determine whether two blobs collide elastically or inelastically) and the rate at which we expect blobs to collide (related to temperature and mean free path for the blobs, I guess). Maybe other factors as well? I'm also just making things up at this point.

I feel like the extreme-long-term result should be a fluid sphere with exactly two layers, with the shape determined by which of water and oil prefers an interface with vacuum/air/whatever medium the experiment is conducted in.

>>8882676
Actually entropy can stay constant. It just cannot increase.

orderly appearance =/= lack of entropy

>>8882911
*decrease

>>8882676
its non decreasing actually

>>8882676
Please calculate the actual entropy of the fucking system you fucking retard.

>this fucking thread
you fucking kids are giving me an aneurysm
don't talk about entropy unless you have a phd

Learn what entropy is

>>8883309
>>8883315
Entropy is porn with big black women right?

>>8883348
i wish

>>8883348
I think you're thinking of ebonytropy

File: 1491438665554.jpg (38KB, 396x385px) Image search: [Google]

38KB, 396x385px

>mfw people in this thread don't understand the hydrophobic effect.

The entropy is greater if they are unmixed, so the entropy is already maximised, at least in terms of mixing/non-mixing. Other stuff could happen like temperature changes or evaporation.

>>8882676
>brainlet musing: do my homework edition

>>8883429
what do you expect from a bunch of mathfags