# Air Particle Density inside the Bubble

Since the bubble takes up volume, we should represent the air particles inside the syringe around the bubble with something less than 35 dots. But wait, isn’t there air inside the bubble itself? How should we represent those air particles? With dots, of course! But how many?

Should we represent the air particles inside the bubble with one dot? Four dots? Ten dots? How do we decide?

There is no way to know for sure, so we are going to use a little common sense. If the air particle density inside of the bubble is greater than the standard air particle density all around us and inside the syringe, then the bubble would be filled up all the way. However, since the bubble is a little limp, we know it isn’t filled up all the way. If the air particle density inside of the bubble is less than the standard air particle density all around us and inside the syringe, then the bubble would shrivel up even more. So we are going to assume that the air particle density inside of the bubble is about the same as the standard air particle density all around us and inside the syringe. To my eye, that looks like the middle picture—the one with four dots inside the bubble.

You should notice that if we combine the four dots inside the bubble with the thirty-one dots inside the syringe around the bubble, we still have a total of 35 dots. The plastic that surrounds the bubble does take up some space (so there is a little less space for air inside the syringe + bubble), but the volume of the plastic itself is so small that it doesn’t make much of a difference.

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