Hi, I'm Robin Higgins. And this is information on the chemistry term buffer. Alright, so a buffer in chemistry has the same general use as a buffer in real life or everyday language. And so in chemistry, we use buffers when we're talking about acids and bases. So, let's say that we have a solution and we want to add a strong acid, but we want the pH to stay the same. So, hydrochloric acid is a strong acid. Let's say this is a cup of water right now. So, if we put hydrochloric acid into water, it will dissociate into positive hydrogen and negative chlorine. And this positive hydrogen is what makes something acidic. So, when you're measuring pH, all you're doing is measuring the concentration of how many of these guys you have. If you have a lot, it's acidic, if you don't have very many at all, it's basic. So, if we want to add this HCL to the water, if we do that right now, the pH is going to skyrocket. But we want it to be stable. So what we're going to do is use a buffer. And so, a buffer is a large amount of a weak acid and it's conjugate base. So, an example is sodium bicarbonate with its conjugate acid. So these two molecules are actually the same, except for the difference in one proton. So you have this guy, H-two-CO-three (H2CO3). And then, in solution, this sodium is going to become positively charged and be by itself. And you'll have a negatively charged bicarbonate molecule HCO-three (HCO3). Alright, so these two guys are conjugate acids and base pair. And so this is our buffer. If we add a bunch of this, then what it kind of does, it acts as a sponge. Because you're allowing something to be in solution or react with an acid or a base. So, let's say that we have our water, but now we actually also add this buffer. And so, now we add the acid, which was our goal in the first place. And we put the HCL in. And now, every single positively charged hydrogen is just going to run into one of these negatively charged bicarbonate molecules. And they'll just form the conjugate acid, which we already have solution. So basically what we're doing is we're creating a trap for these hydrogen ions to fall into our buffer solution. And works the same for bases too, if we added a bunch of hydroxide ions. This acid would donate one of its hydrogens to it and then, it'll become water and bicarbonate again. So, no matter what we do, now we're not really changing the pH because we're not really changing the overall concentration of H plus or O minus. We're just changing the concentration of our buffer solution which we don't care about. So, there's lots of different buffers and you use different buffer depending on what overall pH you want your solution to be at. So, it's kind of like a sponge. I'm Robin Higgins, and this is what is the definition of buffer in chemistry.