 Today I'd like to talk to you a little bit about acids and bases and buffers and some of the properties that you will see when you're investigating them or that you might expect when you come across them. The acids will produce H-plus ions in solutions. They can also be classified as a proton donor. When you think about it, the H-plus is essentially a proton because you've lost an electron and all you have left is a proton. So H-plus produces it, it's a proton donor. If you were to taste an acid, it will taste sour. If you stick litmus in it, the litmus will remain red. It will not turn blue. I would recommend this, although we do mention the taste of acids and bases, it is not a preferred thing for you to use that as your test. In fact, it is a very bad thing to do chemically because of the dangers involved. The base is essentially the opposite of the acid in that it produces hydroxide ion. It is a proton acceptor. If you were to taste a base, it would have a bitter or chalky taste to it and it will turn litmus blue if you put the litmus into a solution of an acid. If you're looking at pH scale, an acid would be from zero to seven. This would be from seven to fourteen and note that seven is your neutral spot. At seven point zero, you are neither an acid or a base, but that's how the pH will differ. When acids and bases react, you essentially have, and I picked two very common examples, I picked hydrochloric acid and sodium hydroxide. When you combine those two, you will form H plus and Cl minus ions in the water. These are both strong electrolytes, so they completely ionize. Sodium hydroxide will form sodium, ion and hydroxide ion. If you combine these two, essentially this is your neutralization equation in which HCl and sodium hydroxide combine, the ions combine, and when they combine, the net result is that H plus plus OH minus will give you water and you'll also have sodium chloride. Sodium chloride is soluble in the solution, so typically you do not see it in as far as you don't see it precipitate, but it is one of those things that is produced from this neutralization. So typically we say that in the acids and bases that are like HCl and NaOH that the net reaction, the neutralization reaction is H plus and OH minus, and it gives you water and a salt. So that's the neutralization process. Now there are times when we need to have solutions that are resistant to changes in pH, and what I want to talk about just briefly is the action of a buffer, but let's talk about what a buffer is. A buffer essentially is a weak acid and its conjugate base. A weak acid, acetic acid is one of the really good examples of a weak acid. Acetic acid is essentially found in products like vinegar, but if you neutralize part of the acetic acid and you form sodium acetate and you have a mixture of sodium acetate and acetic acid, let's talk about what we have in the mixture. You have an acid, an acid will donate protons, you have a base, and if you remember bases will accept protons. And so if you need to keep a pH stable, what happens is that when acid is added into this buffer mixture, the acid will react with your sodium acetate to neutralize. If you were to add a base in to this buffer solution, the base will react with your acid and be neutralized. And so for that reason, these things are resistant to pH change. Let me give you an example of how resistant they are. If you had a beaker of distilled water, let's say you had 150 milliliters of water and you had a pH meter attached to it, the pH of that water we would hope would be somewhere near 7, which is neutral. If I put a drop of concentrated hydrochloric acid into that beaker, the pH would drop from 7 to probably 2 or 3 with one drop of acid. If we did the same thing with a concentrated base to the buffer, I mean to the water, to the same, to another beaker water for 150 milliliters, the pH would change from 7 to 10 or 11 with one drop. If we had a buffer composed of acetic acid and sodium acetate, the drop of acid or base would probably not move the pH at all or you might see a .05 deviation. And this is important because some systems have to have pH to be exactly correct or they will not function. So the acid-base combination resists pH change. Let me tell you where this is very important in to us. In our bodies, we have what's considered to be a physiological pH and the blood can only function and can only exist within a certain very narrow range of pH. And I'm not a biologist, but I will say that it's somewhere around 7-2 to 7-4. Now that's two-tenths of a pH unit. The body uses natural buffers to keep the pH of the blood and other areas stable. When the pH balance is not where it needs to be, then we can have serious health issues. So buffers are important and we see buffers in many areas. You also can see buffers in cosmetic and other types of products that you use. They say that shampoos are pH balanced and they are. They essentially are adjusted so that the pH is such that it is compatible with the hair. But buffers play a big role and I hope that as having discussed acids, bases and buffers this morning that you'll have an appreciation for them and that it will help you in your studies. Thank you.