Why convection happens when concentration gradients exist?

In summary: Thank you for your explanation! It is vey clear and easy to understand, maybe it is a problem of statistics as you explained, the force which result in the uniform distribution of the molecules is not important.
  • #1
lionelwang
23
0
Hello, everyone!

I could not imagine what force makes this convection under concentration gradients , no matter how hard I thought.
Maybe we can use principle of entropy increase to explain it, but that is not vivid to me.

anyone can help me? Thans!
 
Physics news on Phys.org
  • #2
Consider a closed container which we mentally divide into two equally shaped and sized sections, denoted the left and right sections.

If at zero time there are a million particles in the left side, and no particles in the right, and all these particles are bouncing around randomly, how many particles would you expect to end up in each section if we wait long enough for the average number of particles in each to be constant?

Naturally half will end up in each section. So during the waiting period, half the particles moved to the right, due to the concentration difference. This is the diffussive flow, which as you suggest is due to the entropy increase. There is only one way to have all particles in the left compartment but very many ways to have half the particles in each compartment.
 
  • #3
Thank you for your explanation! It is vey clear and easy to understand, maybe it is a problem of statistics as you explained, the force which result in the uniform distribution of the molecules is not important.



jVincent said:
Consider a closed container which we mentally divide into two equally shaped and sized sections, denoted the left and right sections.

If at zero time there are a million particles in the left side, and no particles in the right, and all these particles are bouncing around randomly, how many particles would you expect to end up in each section if we wait long enough for the average number of particles in each to be constant?

Naturally half will end up in each section. So during the waiting period, half the particles moved to the right, due to the concentration difference. This is the diffussive flow, which as you suggest is due to the entropy increase. There is only one way to have all particles in the left compartment but very many ways to have half the particles in each compartment.
 

1. How does convection occur when there are concentration gradients?

Convection occurs when there is a difference in temperature or concentration between different parts of a fluid. In the case of concentration gradients, the fluid will move from areas of higher concentration to lower concentration in order to reach equilibrium, causing convection.

2. What is the relationship between concentration gradients and convection?

Concentration gradients and convection are directly related. A concentration gradient is the driving force behind convection, as the fluid will naturally move from areas of higher concentration to lower concentration in order to balance out the concentration levels.

3. Why is convection important in scientific research?

Convection plays a crucial role in many scientific processes and experiments. It helps to mix and distribute substances, transfer heat, and maintain temperature and concentration gradients. Without convection, many scientific processes would not be possible.

4. Can convection only occur in liquids?

No, convection can occur in both liquids and gases. As long as there is a difference in temperature or concentration, the fluid will move and cause convection. This can be seen in phenomena such as wind and ocean currents.

5. How is convection different from diffusion?

While both convection and diffusion involve the movement of substances, they are fundamentally different processes. Convection is the movement of a fluid as a whole, while diffusion is the movement of individual molecules. Convection also requires a concentration gradient, while diffusion can occur even without a gradient.

Similar threads

I How can concentration gradient field come into existence immediately?
    • Other Physics Topics
Replies
0
Views
319
Mass transfer coefficient from a numerical model
    • Materials and Chemical Engineering
Replies
1
Views
2K
I Integrity of matter / space and time
    • Other Physics Topics
Replies
13
Views
3K
Understanding Diffusion: The Relationship Between RMS and Fick's 2nd Law
    • Other Physics Topics
Replies
1
Views
2K
Concentration gradient force Vs. electrical gradient force
    • Biology and Medical
Replies
4
Views
8K
Biology What Happens When Ran GTPase Binds Tightly to GEF?
    • Biology and Chemistry Homework Help
Replies
7
Views
1K
Exam help regarding heat exchanger, forced convection questions
    • Mechanical Engineering
Replies
7
Views
2K
I Concentrated arcs in bubble chamber photos
    • High Energy, Nuclear, Particle Physics
Replies
2
Views
1K
I Can buoyancy exchange still happen in a gravitational fed water system with closed hydraulic head?
    • Thermodynamics
Replies
2
Views
666
I Can concentration gradients be related to information?
    • Atomic and Condensed Matter
Replies
1
Views
836

Hot Threads

Recent Insights

Back
Top