 Okay in this next exercise we want to demonstrate how buffers work and also we want to demonstrate the indicator bromethyl blue. So to start the demonstration I am going to pour 25 milliliters of pH 7 buffer solution into a beaker and then I'm going to pour in 25 milliliters of water into a beaker. So this beaker contains 25 milliliters of the pH 7 buffer solution. This beaker contains 25 milliliters of water. Next we're going to add the indicator bromethyl blue and add about 20 drops. A little stir. You can see that we have a nice blue color there. I'm going to add the same approximately to the water and what I'm going to do is I am going to add hydrochloric acid to the buffer solution. I'm going to add it one drop at a time and I'm going to stir gently. So there's one drop, whoops, that was three drops, two came out at once. You notice that it's changing more from a blue color to a yellow color. There's four drops, five drops. Now let's compare that to water. You see now we have a sort of a greenish color and we're going to drop this one drop in the beaker of water, stir and you see immediately it turns very yellow whereas this is still more of a green. If I squirt the remainder of the dropper in there I can have them both turn a nice yellow. So at a pH below seven bromethyl blue turns a yellow color. It took many more drops of the hydrochloric acid to turn the buffer solution from blue to yellow as opposed to the water. Now just for fun let's add a base to each solution. This is one molar sodium hydroxide solution and I'm just going to add a few drops in here as I stir. That's 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31. I'm starting to see a little blue, 32, 33, 34, 35, 36, 37, 38, 39, 40. You see we're coming back blue as we're getting closer to a pH of seven. That's about 50 drops, 60 drops and we're back to a blue color. Let's see what we have here. Three drops and we're back to a blue. So the point of a buffer is buffers prevent rapid changes in pH by converting strong acids into weak acids and by converting strong bases into weak bases.