So now that we've introduced acids in our previous lesson videos, in this video we're going to introduce bases. Bases are practically the opposite of acids, and that is because, instead of increasing a solution's hydrogen ion concentration, bases are any chemical that decreases a solution's hydrogen ion concentration or concentration of hydrogen ions. An example of a base is sodium hydroxide, whose chemical formula is NaOH.

If we take a look at our example image below, we'll be able to see an example of a base, specifically the addition of Sodium Hydroxide or NaOH to water. Notice on the left hand side over here what we're showing you are three different Sodium Hydroxide molecules, 1, 2, and 3. When each of these sodium hydroxide molecules is added to water, the sodium hydroxide is going to dissociate, or break apart, or ionize into these ions. For example, this Sodium Hydroxide molecule will break apart into a Sodium ion or Na⁺ and a hydroxide ion or OH^-. This is going to be true for each of these sodium hydroxide ions.

Notice upon the addition of the Sodium Hydroxide to the pure water, the ions are going to break apart. So, you'll see three hydroxide ions and three sodium ions. Now you'll notice that even in pure water over here we're showing you some hydrogen ions, and this is going to be true even for pure water there will be some hydrogen ions. This is because water has the ability to auto ionize, which is something that we'll get to talk more about later in our course. For now, notice that there are some hydrogen ions even in pure water, and so you can see those hydrogen ions over here as well.

What's important to note is that each of these hydroxide ions is going to interact with a hydrogen ion, And so you will see these interactions right here, and when the hydroxide interacts with the hydrogen ion, they create water molecules, as you see right here. What you'll notice is that the concentration of hydrogen ions is being decreased because of the addition of this sodium hydroxide. Whereas there were three hydrogen ions in the pure water in this beaker here, in the final beaker, notice that there are not any hydrogen ions being shown, and so what this is showing is the decreased hydrogen ion concentration.

Once again, when a chemical decreases a solution's concentration of hydrogen ions, that chemical is referred to as a base. So, sodium hydroxide is indeed a base. The concentration of hydrogen ions is incredibly relevant to living systems, and so any substance that can change the concentration of hydrogen ions is going to be relevant as well, and so bases are very important. This here concludes our brief introduction to bases, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.