This must have been posted on here before, but I can't find any reference to it. I've had to learn a little biochemistry related to my work. This led me to realise that I knew little chemistry, and set me out to learn some chemistry. Chemical reactions are significantly dependent, according to what I read, on entropy. This got me looking at entropy again, which I remember vaguely from school. Some books try to explain entropy in terms of order/disorder. This seems a bit of a poor explanation to me. For example, they show a box with two gases in it separated by a barrier: the barrier is removed, and the gases mix. Thus order -> disorder, and the entropy increases. This still seems to beg the question of what "order" is. Also it helps not one whit when trying to explain what entropy means when you are trying to define Gibbs free energy. An attempt I came across to tighten up the gas-dispersion explanation of entropy stated that it was a movement from low-probability state to a high-probability state. Of course, in this example this is nonsense, because any particular arrangement of gas particles is as equally probable as any other: we only have a "higher-probability", as we have grouped a larger number of particular arrangements into a single category, and so therefore a category with a large number of arrangements ("dispersed") has a higher probability than a category with a lower number of arrangements("compacted"). We can arbitrarily create any kind of categorization we like to describe arrangement of gas particles. Thus entropy and chemical reactions depend on what categories we choose to define. This seems very improbable, or at least a very confusing explanation. Then there was the attempt to explain it in terms of information. We have good information on where the gas particles are at the start, the instant the barrier is removed. As the two mingle, we have less information on the relative locations of the gas particle of one kind relative to the gas particles of the other kind. This is really just the same as the order/probability explanation given before, but in different terminology. Still the same problem arises: does a chemical or physical reaction depend on how much knowledge we have about a system: surely the chemical and physical event occur even if don't know about them. And even if we had perfect knowledge, the reaction would still happen. We in fact do have pretty good knowledge of the reaction that occurs when a chromosome replicate itself: we know the structure of the chromosome, and the intermediate molecules that read it, and reconstruct its copy. Our near-perfect knowledge has no effect on the reaction. So we'll drop this order/probability/knowledge analogy, unless someone explains it better to me.