Concentration

What do we mean when we say concentration? Typically, we define it as the amount of stuff you have in a certain solution. So, let's say I dissolve one pound of sugar in one gallon of water. The concentration of the sugar is one pound per gallon. If I took a small sample of that solution, let's say a quart, what would the concentration of the sugar now be? That's right, one pound per gallon. Now, the amount of sugar is not one pound, but the concentration is!!! In fact, we know that there are four quarts in a gallon, so we have one-quarter of a gallon. If we know that we started with one pound of sugar in one gallon of water, and now we have one-quarter of the solution, we will have one-quarter of a pound of sugar. But the key is that the concentration is still the same!

Concentration is an easy way of describing how something changes during the course of a reaction. We use concentration when we are dealing with solutions, because typically, we say that we have a certain number of grams of substance in a ceratin amount of water.

As concentration decreases with time, we can say that the amount of substance that we started with is decreasing as well. Let's say we have the one pound per gallon sugar solution. If we add a few grams of an substance that reacts with sugar, like acid, it will decrease the amount of sugar in the solution. This will decrease the concentration of the sugar in solution, and increase the concentration of the product (which is the result of a small amount of acid reacting with sugar).

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