In an irreversible change, this is a change that is permanent and cannot be undone to restore the original structure. So when we undergo our irreversible change, we can't go backwards. We're stuck with whatever we make. Now, the most common example of irreversible changes deals with chemical changes. Remember, chemical changes alter the identity of our original material.

A great example here is we have nitrogen gas, hydrogen gas, and together they combine to give us NH3 gas. They have chemically bonded to each other, N2 and H2 to form our compound of NH3. And because they're chemically bonded this way, it's going to be an irreversible process. Okay? So we're going forward in one direction. Once we've made that NH3 group, we can't go backwards and remake our N2 and H2 by normal conditions. So just remember, an irreversible process creates something brand new and it forever alters the way our original material was. We can't go back to it, at least not by normal means. Right.

Now that we've seen the difference between reversible and irreversible processes, let's click on the next question and let's tackle some example problems.