Life sciences, cells, and material movement / principles and exploration
Diffusion and concentration gradients — principles and investigation
Like the phenomenon of scent spreading, diffusion occurs in the random movement of particles. Change the initial number of particles and partition conditions in the two spaces and compare the time changes in the number of particles on the left and right. This is an experiment to observe the meaning of dynamic equilibrium, which means that particles continue to move even after the concentration difference is reduced.
How does it work?
The concentration difference decreases, but random movement in both directions continues even at equilibrium. The total number of particles is preserved.
Total number of particles N = N left + N right
Try this investigation
- Compare open and closed partitions. Green is the number of particles on the left, and purple is the number of particles on the right. Look at the trajectory of one orange particle and the number of passes in both directions.
- Record the two conditions with the same seed and initial numbers, only changing the state of the partition.
- See if two-way passes increase even if you start at 80:80. We also compare sample changes based on records where only the seed has been changed.
Interpreting your results
Why do left-to-right and right-to-left crossings continue to accumulate at equilibrium?
Even in equilibrium, movement in both directions continues. In small samples, the number of left and right particles is not exactly the same and constantly fluctuates.
Assumptions and limitations
It is a 20×12 grid probability movement model of two spaces of the same size and a single particle species. Particle collision, volume, and electric force are omitted and a maximum of 400 are used. Concentration is compared by the number of particles in the same space. The stop at the end of the observation section means that time has stopped playing. It's not actual molecular suspension.