What drives the process of diffusion?

But yes, looking at all of them together, they all equalize with each other. In summary, diffusion is governed by the movement of molecules and their tendency to follow the path of least resistance. This is influenced by various factors such as inertia, electromagnetism, thermal energy, statistical mechanics, and quantum uncertainty. The process of diffusion can also be explained by the Second Law of Thermodynamics, which states that systems tend towards entropy. In the case of gases, diffusion leads to the equalization of partial concentrations due to the ideal gas law.
  • #1
Homer
Hello,
In a biological course in the university, I asked my professor Which force governs diffusion and He didn't know.
Note that i don't mean Fick's first or second law, Einstein's law of diffusion, the Brownian Motion and not even the The Second Law of Thermodynamics, simply what "compels" particles to move and thus to balance concentrations.
For example, falling objects towards Earth is governed by the universal law of Gravitation
Any ideas?
Thanks
 
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  • #2
I would think it's the fact that all things follow the path of least resistance. I suppose that's not governed by one of the "forces", but is rather a principle that allows the "forces" to work. IOW, the "forces" (or curvatures in spacetime (please, everyone, don't side-track the thread just debate this point)) only influence an object's actions because that object is inclined to follow the path of least resistance.
 
  • #3
Try inertia, electromagnetism, thermal energy, statistical mechanics and quantum uncertainty. One cannot easily ignore the theories/laws you referred to, though.
 
  • #4
I would agree with Mentat, the main force of diffusion is that molecules move, they bounce against each other and transfer energy between them. An over-symplistic model: think of a large square area w/ horizontally moving walls. You put some tennisballs in one corner, the bouncing wall will set the tennisballs in motion, after which they bounce and bounce until all the forces are distributed evenly and the balls have 'diffused' over an area and are homogeneously spread out.

LBooda, could you explain what you mean by statistical mechanics and how quantum uncertainty facilitates diffusion?
 
  • #5
Statistical mechanics is a classical method which involves both qualitative and quantitative assessment of many similar particles interacting thermally. Atoms numbering on the order of Avogadro may be modeled in a closed system (say a box with sides of length x) toward the distribution of states (say quantum numbers). Although every possible state of a particle has an equal probability, the constraint of thermal equilibrium requires a very well defined overall statistical distribution of states in relation to, say, temperature. You may have heard of the Boltzmann distribution, which gives the population of classical particles (most atoms and molecules) as a function of energy or temperature.

Einstein showed in 1905 that Brownian motion, a process much like diffusion, is a quantum mechanical process. Basically, each particle in suspension has an uncertainty in position and velocity associated with itself that manifests as random motion. This movement overcomes the bonds present in the liquid, and diffusion procedes.
 
  • #6
Originally posted by Loren Booda
Try inertia, electromagnetism, thermal energy, statistical mechanics and quantum uncertainty. One cannot easily ignore the theories/laws you referred to, though.
I have always thought of it simply as : Anything above absolute vibrates. (thermal energy) If particles such as atoms and molecules are close to each other, they will in due course vibrate into each other, and so 'bounce' off away from each other (electromagnetism causes this). In this way, over time, they will tend to bounce away from each other, causing an eventual tendency for them to keep pushing outwards. The less close the molecules are to each other, the less they will push away from each other.

This is also related to 2nd Law of Thermodynamics. Diffusion, is the system tending towards entropy.
 
  • #7
To paraphrase my former stat mech prof, "It's just a simple case of understanding chemical potential and knowledge of what diffusive equilibrium is!"

Heh.
 
  • #8
Originally posted by Loren Booda
Statistical mechanics is a classical method which involves both qualitative and quantitative assessment of many similar particles interacting thermally. Atoms numbering on the order of Avogadro may be modeled in a closed system (say a box with sides of length x) toward the distribution of states (say quantum numbers). Although every possible state of a particle has an equal probability, the constraint of thermal equilibrium requires a very well defined overall statistical distribution of states in relation to, say, temperature. You may have heard of the Boltzmann distribution, which gives the population of classical particles (most atoms and molecules) as a function of energy or temperature.

Einstein showed in 1905 that Brownian motion, a process much like diffusion, is a quantum mechanical process. Basically, each particle in suspension has an uncertainty in position and velocity associated with itself that manifests as random motion. This movement overcomes the bonds present in the liquid, and diffusion procedes.
Thanks for that great explanation :)
 
  • #9
Hey,
Thanks for the responses.
I have a follow-up question then.
If random walk and Thermal energy do indeed govern diffusion, why is it that each gas tend to equalize its partial concentration only with regard to itself.
E.g. If we intermix two systems of oxygen and helium, each gas will achive equilibrium only with its own kind (so to speak).
Thanks.
 
  • #10
Partial pressure arises from the ideal gas law p=nkT, where n is the sum of the number of molecules of the constituent gases. Thus p is pressure of the contituent gas "c," where pc=nckT.
 
  • #11
why is it that each gas tend to equalize its partial concentration only with regard to itself.
Partial pressure arises from the ideal gas law p=nkT
Thats not how it works, but not WHY. Homer, if each component gas equalizes with itself, then they also all equalize with each other. This is part of diffusion and the same concepts apply.

You can look at each gas by itself or all together. The rules are the same. Its just easier to look at each one individually.
 

What is diffusion?

Diffusion is the process by which molecules or particles move from an area of high concentration to an area of low concentration. It is a result of the random movement of particles and does not require any external force.

What is the force that governs diffusion?

The force that governs diffusion is known as the concentration gradient. This refers to the difference in concentration between two areas, which causes particles to move from an area of high concentration to an area of low concentration.

How does temperature affect diffusion?

As temperature increases, the rate of diffusion also increases. This is because higher temperatures cause particles to move faster, increasing the likelihood of collisions and thus increasing the rate of diffusion.

What is the role of size and shape in diffusion?

The size and shape of particles can affect the rate of diffusion. Smaller particles have a higher surface area-to-volume ratio, making them more likely to diffuse at a faster rate. The shape of a particle can also determine how easily it can move through a medium, affecting its diffusion rate.

What factors can affect the rate of diffusion?

Aside from temperature, the rate of diffusion can also be affected by the medium through which particles are diffusing, the size and shape of particles, and the nature of the particles themselves (e.g. polarity, charge). Additionally, the distance between the two areas of different concentration can also have an impact on the rate of diffusion.

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