 Are you ready for some magic? Here's the magic. Chemical reactions can proceed in two directions. They can proceed in this direction as indicated by this arrow. I feel like an earthquake just happened. I feel kind of wiggly. Now, they can also go backwards. Really? Now look at this. How do my chemical reaction go this direction? So the red arrow is indicating a different direction that this chemical reaction can go. And I want you to tell me now, if the chemical reaction is moving the other direction, whatever, if it's moving in this direction, then where are my reactants and where are my products? It matters which direction it's going. I can label reactants and products as long as the equation is moving in a direction. If the reaction is, dude, I'm sensitive, if the reaction is moving in both directions at an equal rate, then that chemical reaction is in what's called equilibrium. Chemical equilibrium is when the rate of forward reaction is the same as the rate of the backward reaction, which is all we're doing is we're looking at the fact that the reaction is happening both directions at the same rate. When a chemical, all chemical reactions will ultimately reach equilibrium if you leave the number of products and the number of reactants. Like if you, you will eventually run out of reactants and you will eventually build up the products. And if you have enough product and not enough reactant, that reaction, when it reaches equilibrium, will move the other direction. If you want, okay, so did you, are you cool with that idea? Let me give you another example. I'm going to draw another chemical equation in here. And this one, you are going to see and see and see and see. We're going to see this chemical reaction in a lot of different places. So it's worth taking the time to get comfortable with it. If you had me for Bio 1, you've actually seen it before. Water and carbon dioxide, does anybody know what that becomes? It actually becomes carbonic acid, H2CO3. And then carbonic acid breaks down into hydrogen ions. And this is the whole acid and base thing. And we're actually going to talk about that today. Hydrogen ions and bicarbonate ions, HCO3 negative. The positive and the negative, this means it's an ion. It's a positively charged ion. This is a negatively charged ion. This is an excellent example of a chemical reaction that comes into equilibrium and will move forward or backward. This chemical reaction, really, we keep removing. We use up the ATP, we breathe off the carbon dioxide, we pee out the water or we breathe it out or somehow we get, we don't have this build up of water. Since we keep getting rid of these products, we keep allowing the reaction to move in this direction. You could overdo on ATP. You could stop that whole chemical reaction if you had too much ATP, if it was like building up. But if you keep removing it, you can keep having the chemical reaction take place. We keep removing that stuff because we easily use up ATP. We don't, we can't store that stuff. In the case of this chemical reaction with this whole carbon dioxide and carbonic acid, in this chemical reaction, you reach dynamic equilibrium. You can watch and be like amazed. This concept is a little tricky. Someday when I have lots of time, when you figure out how to give me another 24 hours in every single one of my days, you do that for me, when you figure that out, then I'm going to make some kind of interactive, dynamic equilibrium thing. Activity that will let you fiddle with this, will let you actually do something like add carbon dioxide molecules. So watch what I'm going to do. I'm going to imagine adding a whole bunch of carbon dioxide molecules into this little dynamic equilibrium system. If I add carbon dioxide, a whole bunch of it, can you imagine what's going to happen to this chemical? Which way is it going to go? If it's in Wendy land, let me tell you how this happens. I imagine like this huge pile of carbon dioxide. If I add carbon dioxide, I imagine like marbles and there's like a whole bunch of marbles and I make this big mountain of marbles. But then that's not going to be sustainable here. We don't want to build up anything. These chemical reactions will go until they reach equilibrium. If I add a whole bunch of carbon dioxide, this system is going to say, dude, we've got to get rid of this stuff. And so it actually is going to push the chemical reaction this way. Can you visualize that? Because if the chemical reaction goes that way, my ways are all mixed up, but if it goes that way, then the carbon dioxide is going to disappear because you actually turned it into carbonic acid hydrogen ions and carb bicarbonate ions. That's what that thing is. So you follow that? In my brain, it's like, I can visualize that. If the act of sending it this direction means that, yeah, we're going to decrease that little pile and the pile is going to get smaller. And pretty soon we're not going to have that much carbon dioxide because you turned it into all of these products over here. And then you're going to be back in that dynamic equilibrium where it's going both directions. If I did something really crazy, crazy, and I added a whole bunch of hydrogen ions, now we've got this pile, this massive pile of hydrogen ions and we've got to get rid of them. Or there's too many on that side. It's going to push the reaction in this direction. Does that work for you? In Wendyland, it makes perfect sense, because this idea is kind of tricky. You go back and forth, back and forth, back and forth, as long as you can maintain that dynamic equilibrium. And it's a chemical reaction that is happening all the time in your body. So think about this one. You ready? I love this visual. Carbon dioxide, hold your breath. What's happening to the amount of carbon dioxide in my system? Dude, I'm getting a big old pile. If I'm holding my breath, right? Because you're not letting that carbon dioxide out. And as you get that bigger and bigger pile of carbon dioxide, what's going to happen to this chemical equation? It's going to push that way, because you're holding your breath, doofah's head. Let's draw it out. That's crazy talk. Now, let's go on to the next one and look at who cares? Hold your breath. Why does it even matter? Let's get an IV of oxygen. I'll just give you all the oxygen that you want. And go ahead and hold your breath. And I'll tell you right now, you're still going to die. Even if I, like, stick oxygen in you, like directly into your blood so that you never ran out of oxygen, you still are going to die. Think about that. Maybe think about what we're going to talk about next on our list and see if you can figure out why that is, why you hold your breath and you get too much carbon dioxide. Why are you going to die anyway? I hope you're breathing right now.