Entropy & Osmosis: Brownian Motion & 2nd Law of Motion

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Discussion Overview

The discussion explores the relationship between Brownian motion, osmosis, and the second law of motion, focusing on concepts of entropy and energy dynamics in systems involving semipermeable membranes. It encompasses theoretical considerations and implications of these phenomena.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the impact of Brownian motion and osmosis on the second law of motion, suggesting that exerting energy in experiments may not relate to these concepts.
  • Another participant asserts that diffusion increases entropy, noting that Brownian motion pertains to individual particles while entropy applies to ensembles.
  • A different viewpoint introduces thermo-osmosis, proposing that particles diffuse towards higher entropy in the presence of an entropy/temperature gradient across a permeable membrane.
  • One participant describes a scenario involving a membrane with holes that allows small particles to move while larger particles remain, suggesting that this creates pressure and energy dynamics.
  • Another participant references Maxwell's demon, implying that even in small cases, the concept holds relevance.
  • A later reply elaborates on the energy conversion aspect of the membrane, arguing that it acts as a lever for converting osmotic potential energy into gravitational potential energy, while also noting that this process does not create energy in a closed cycle.

Areas of Agreement / Disagreement

Participants express differing views on the implications of Brownian motion and osmosis concerning the second law of motion and energy dynamics. No consensus is reached on the relationship between these concepts.

Contextual Notes

Some participants highlight the complexity of relating single particle behavior (Brownian motion) to thermodynamic principles (entropy), indicating potential limitations in definitions and assumptions regarding the systems discussed.

menniandscience
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what exactly browian motion and osmosis does to the second law of motion? nothing right? because anyway one will set an experiment trying to locate semipermeable membrane, he\she already exert more energy.

(i need you to verify me)
thanks
 
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Diffusion of a substance from an area of high concentration to an area of lower concentration will increase the entropy of the system.

Brownian motion is tricky to talk about in terms of entropy. Brownian motion (the random walk of particles) is something that occurs with single particles. Entropy, a thermodynamic concept, applies to large ensembles of particles, not single particles. Of course, the Brownian motion of large ensembles of particles is diffusion.
 
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I think you need to also consider thermo-osmosis. Or that, in a permeable membrane which has some sort of an entropy/temperature gradient, particles will always diffuse towards higher entropy since it is thermodynamically favored.
 
well it is a difussion if the membrane got holes alowing only small objects move both sides and big stay in one side. you build a pressure, when you remove the membrane there is energy, and that is not just a few particles but a large quantity of microscopic particles
 
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and Maxwell was right, there can be a demon, even if it is in a small case
 
meni ohana said:
if the membrane got holes alowing only small objects move both sides and big stay in one side. you build a pressure, when you remove the membrane there is energy [...] and Maxwell was right, there can be a demon, even if it is in a small case
The membrane is just a lever for converting the osmotic potential energy (that you prepared) into gravitational potential energy (which you know how to harness). You can tell that it isn't creating energy by the fact that, unlike Maxwell's demon, the operation of your device can't repeat in a closed cycle (you have to perform more work to separate back the solutes first).
 

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