That's because the lowest energy state for the solution is for the salt to be even distributed so the salt concentration is the same everywhere.
If you had a region in the solution where the concentration was 19% then salt would mix in from the rest of the solution to bring it back to 20% again.
So the salt concentration is going to be 20% everywhere in the solution.
Yes, I should have said sodium and chloride ions rather than salt molecules. But it also applies to things like sugar that don't dissociate in solution but stay as molecules.
If the concentration is the same everywhere this random movement doesn't have any effect because all the molecules move around randomly and on average the number of molecules per unit volume remains constant.
But suppose you have a region where the concentration is low. The rest of the solution around the low region has a higher concentration. That means on average more molecules move into that region than move out of it, so the random motion increases the number of molecules in the low concentration region.
The result is that the concentration rises until it becomes the same as the solution around it.
@JohnRennie I have a silly question. Force makes an object accelerate. That’s because F=ma. Motion depends on this equation. So what if there is a force and we don’t solve the equation. Will there be no acceleration?
I am asking if motion depends on this eqn and we don’t solve the equation what will happen? Why are we taking the extra step to solve the equation if say Force is given ?
So by knowing F=ma we can understand and predict the details of the motion. Why this is happening. But not having the eqn in our inventory does not mean nature will stop behaving the way it does. Nature does not depend on this equation. We cannot say this is happening because of this equation.
@JohnRennie I remember you saying when a light ray is passed through a slit, it wavefunction changes (causing photons to deflect by an angle) so we are seeing interference pattern, But how can a light wave simply deflect because it is passing through a slit ?
Problem Solving Strategies
Problem Solving Strategies