Diffusion: How Molecules Actually Move 

Thank you! Please consider sharing where you can. The first 10K subscribers are the toughest to find, I think.

Thank you! Working on it, I have a couple projects in the works

Osmosis is a more complicated and confusing phenomenon. I hope I can make a video on it at some point

@@biocinematics Oh, Ok thanks for replying and kindly consider making a video on it.

You too have an awesome underrated channel

@@Sivah_Akash thanks :D

Thank you! I used Houdini for the simulations. It's widely used in the entertainment industry for VFX.

I'm so glad it helped!

Thank you! I'd be happy for you to share the video on twitter. You can also tag me (@biocinematics). I've got a new video coming out next week which I think you might like as well.

@@biocinematics Sure gladly! I can't wait to see it.

No promises, but it's a good suggestion. I've been thinking about a follow-up

Thanks! It's a good question, I'm probably not fully equipped to answer, but I'll give it a shot. Pressure and concentration are related, but not quite the same thing. I think of pressure as a force resulting from the frequency of particle collisions in an area (e.g. air pressure against bird wing), whereas concentration is the amount of a specific molecule type or multiple types in a volume (e.g. CO2 concentration). When a bird wing pushes down, there's an equal force from the air pushing up, in the same way as your hand on a table pushes you up. For a bird wing, having a low pressure area above maybe factors in too, in which case you have more particle collisions from below than from above, adding to the upward force. I'm no aerodynamics expert, so I'm just making educated guesses really. Hope it helps a bit though.

Salt diffuses in water once some of it dissolves and is no longer a solid. I can't think of any examples of true solids diffusing into another solid, because solids hold together by definition. In other words the random thermal motion of the atoms and molecules isn't vigorous enough to leave its neighbours.

@@biocinematics how about vacancy diffusion though. It rares but exist

Not technically wrong, but I'm trying to demonstrate that for all practical and measurable purposes, the probability is essentially zero. 2nd law of thermodynamics and all that.

@@biocinematics, oh. But since entropy can never decrease, is the possibility of not diffusing zero or is that not true?

@@Sivah_Akash There can be other forces or energy used to prevent or reverse diffusion, (e.g. active transport across a membrane) but in systems without additional forces or energy used, diffusion will proceed and entropy will increase as a result. Does that answer your question?

@@biocinematics, yup it does. Thank you. One more question. So does that mean without any other forces, there not even a tiny chance of reverse diffusion? However small that probability is?

@@Sivah_Akash I guess it kind of depends on what you mean by reverse diffusion - how many molecules, what kind of concentration gradient and for how long. There's a chance that several molecules will travel against the concentration gradient temporarily (as you see in the video), but the more molecules you look at, and the longer they move, the probability of large-scale reverse diffusion approaches (but doesn't quite reach) zero. That's my understanding, anyway.

Fantastic question. I had to look up some stuff, and I'm probably not the best person to answer, but here goes. If you consider conduction, that's transfer of heat by direct contact. In other words, if you have a hot piece of metal, the atoms are jiggling very fast, and if you put that into water, the fast jiggling metal atoms will collide rapidly with the water molecules and make them move faster, thus increasing the average speed of the water molecules (and cooling down the metal, because some of the kinetic energy is transferred - think about billiard balls hitting each other). Now the harder part: how does radiation work, like how the sun heats up the earth? There's no direct contact between atoms. It turns out that certain wavelengths of radiation, like infrared, are "resonant" with the natural jiggling of atoms and helps increase the motion. Not unlike a certain frequency of sound causing a wine glass to resonate and vibrate more. That's an incomplete answer, but I hope it helps.

@@biocinematics ahhh i get what you're trying to say. Thanks for replying. I should do more research on radiation then :3. Nothing better than satisfying the inner curiosity in qurantine...