And the other six molecules, let's call a molecule B, are found on the right side of that fluid filled container. Now, separating the left and the right side is a semi permeable membrane that allows both of these molecules to basically pass through. The question is, what exactly will take place over time? Well, over time, we're going to get the following case in which we're going to have equal amounts of molecule A on both sides and equal amounts of molecule B on both sides. Basically, as a result of Brownian motion, molecules A and molecules B will be in a constant state of motion. And based on the law of entropy, the most mathematically probable state of our system is in which we have an even amount of molecules on each side.