Guys, how does osmosis occur? Like really occur. I just have this feeling that no body really knows...

That would be my guess, it checks out with everything i know ‘bout intermolecular forces.

neat

I like to think about it like so, water is level between the film without the salt. When you add the salt on one end it sorta makes the water not level. But since the salt can make it to the other side it doesn't matter that it isn't level. Or is this a flawed way of understanding it and concentration is the only way of thinking about it

/thread

>
There is a difference in chemical potential between the two sides, and chemical potential changes with concentration.
One side increases in concentration, and the other decreases.
One side increases in chemical potential, and the other decreases.

Do you mean Capiche?

Basically, the particles really hate being close to each other and the more solvent there is for a given number of solute particles, the more living space they can have.

This pleases the particle.

They go to great lengths to annex this liquid, drawing it into their volume and assimilating it into their regime by force until everybody has roughly the same distance from their neighbors as everyone else.

Concentrations tend, spontaneously, to even out. If there are equal amounts of water of both sides but you add salt to one and leave the other pure, fresh water will diffuse through the barrier to make the salty side less concentrated. Yes, work is being done (there could be a piston floating on the salt water and it would rise as fresh water entered) but entropy is increasing and the free energy is diminished.

To go in the other direction -- reverse osmosis, making fresh water from salt water -- you have to force water molecules through the barrier while the salt stays behind. This requires DOING work, applying pressure to the salt water.

This is why physics is retarded. Literally nobody in this thread has answered the question, they've just recited more definitions. "To lower the potential energy", "because of electromagnetic forces", "entropy', these are just bullshit terms.

You are literally just explaining phenomena through efficient causes. Give me the final cause, WHY the FUCK does nature want to reduce its potential energy, and why does it use osmosis to do so?

Potential energy is just a formal way of quantifying instability. If you have one side with a concentration that is much greater, the forces are unbalanced and thus shit moved around. WHY does this happen? BECAUSE with every bit of matter comes a set of properties that force it to interact in such a way.

I said entropy increases.
Do you understand entropy?
It's a measure of the possible microstates a system can be in. If you open a can of soda in a sealed room, the gasses will rush out and fill the room. Having them randomly mixed throughout the room is more probably than having them all compressed in the can.

Look at it this way. Molecules are always zipping around, right? They bounce off the walls and keep going. Suppose the can has an inner surface area of 10 square inches and an opening of 1 square inch. Suppose there are 1 million molecules n the can. Any random movement of a molecule in the can has 1 chance in 10 of passing through the opening.
Suppose the room is 10 feet cubed. Its inner surface is 86,400 square inches. The same 1 million molecules are dispersed throughout the room. Each time one hits a wall it has 1 chance in 86,400 of hitting the opening of the can and going inside. That's unlikely. So the gas is mostly going to fill the room.
When the concentration of molecule per cubic foot is the same in the can as it is in the room then, on average, as many molecules enter the can as leave it. It's in equilibrium. But notice, almost all the molecules are in the room and not in the can. Only the concentrations are identical.

If there's a barrier preventing the salt from moving, the only way to equalize concentrations is for the water to move.

>"To lower the potential energy"
This is the abstract concept.

>because of electromagnetic forces
This is the mechanism.

>[Gibbs and helmholtz]
This is the quantification.

It's all there, just piece it together faggot.

>It's a measure of the possible microstates a system can be in.
Liar. It an analogous to it and follows that trend, but it is not the same thing.
I am fucking tired of this normie disorder meme, all it does it confuse people and make people feel smart over false understanding.

Fucking entropy. Dumbass

Literally what are you smoking. That is literally what entropy is.

That's literally the Boltzmann form of entropy
S = k ln W

found the physical chemist

The second picture does actually happens, yes

Nobody really knows for certain. You're right that the entropy/potential energy/activity/thermodynamics are phenomenological observations that *describe* osmosis, but they don't explain the mechanism.

However, the best theory I've seen is that molecular forces are "rectified" across the membrane. Since the membrane is permeable to a water molecule, when water molecules impact the membrane, they will either reflect and impart a mechanical force which will eventually make it to the other side of the membrane (via thermal equilibrium) or they will absorb into the membrane matrix and transfer their momentum to the membrane. Without any salt, these collisions and absorption events are balanced across the two membranes.

When an impermeable osmolyte is present, the osmolyte molecule collides with the membrane surface and is reflected off of it -- it never enters the membrane, so momentum can't be balanced between the two solutions. This results in a pressure on the membrane surface. To rectify the pressure difference across the membrane, water molecules are pulled/pushed through, as a result of the reflected collisions of the osmolyte.

I think a key observation is that, for polymer desalination membranes, the membranes appear to act identically under osmotic and mechanical pressures. Solution-diffusion theory predicts that the upstream side of the membrane contains water very close in concentration to what the membrane would have under free swelling in pure water while the downstream side will be become drier as driving force increases, resulting in a flux of water.

Since the transport coefficients of membranes appear to be mostly consistent in osmosis-driven and pressure-driven experiments, this implies that the mechanism of transport is similar -- osmotic pressure does appear to manifest itself as a real pressure at the microscale, even though the osmotic pressure isn't defined for two solutions in direct contact.

You might also consider that there's no fundamental difference between osmotic transport and vapor transport in an isopiestic (vapor pressure) osmometer -- the "membrane" is replaced with air, the diffusion coefficient in the membrane is replaced with the diffusion coefficient in air, and the sorption coefficient is replaced with the vapor pressures above each solution. The mechanisms of vapor-liquid equilibria are much better understood.

dspace.mit.edu/handle/1721.1/29859

Why does reverse osmosis water filtration often need a pump to maintain pressure to work?

Because you're doing work to separate the water from the dissolved materials.

Because each particle of solute gets surrounded by a small gang of water molecules which is understood geometrically due to molecular interactions, look it up. The net result/macroscopic disparity in water levels is then a function of the total number of particles for each side of the partition.

B a l a n c e

>what are you smoking
A meaningful definition with actual utility.

I always think of osmosis in the body to help me. If there is more solute outside of the cell (in this case), the cell’s water will go outside of the cell to equalize the solute concentration.

So that’s why if you drink too much water, your cells will have higher solute concentration and so water will flood the cells (bad) and likewise if you are dehydrated, the water inside the cells goes outside to lower the heightened salt concentrations and the cells shrivel up.

It doesn’t matter where the water is, only the amount of solute concentration.