system
Given the following post, respond as if you're commenting on Reddit:
human
Le Chatelier's principle - How do the reactants "know" that the concentration of products has changed?

If you get rid of product as it is made, then the equilibrium will shift to further favor products, right?  Why does having lower concentration of products make the reaction more likely to happen?
gpt
No given molecule "knows" anything - you're right about this. The thing is that every molecule in a reaction has a probability of being in the first or second state. 

When you reach equilibrium, that's when the probability of forming the reactant or product (state 1 or state 2) balance. Molecules in state 1 have a probability of converting to state 2, while molecules in state 2 have a probability of converting back to state 1. When these rates balance out, the system is at dynamic equilibrium. 

This doesn't mean that interconversion isn't happening, but that it's happening at balanced rates and the *net change* is zero.

Le Chatelier's principle addresses what happens when you remove molecules in state 2 from the solution. This can be by many means, a common one being by a phase change - molecules in state 2 are much more likely to evaporate or precipitate into gas or solid. 

If you remove a bunch of molecules in state 2, then you still have just as many molecules in state 1, which have the same probability of converting to state 2. But you now have *less* molecules in state 2 that can convert to state 1. As a result, you get a **net** conversion towards state 2. If you continue to remove state 2 molecules, more molecules will convert to state 2 until they are at the concentration where conversion back from state 2 balances the probability of conversion from 1 to 2. 

This works in reverse as well, if you add a bunch of state 2, and have more state 2 molecules than are normally generated by conversion from state 1, you will have a net production of state 1, pushing the equilibrium toward the production of more state 2 to balance the rates of conversion again.