Will the air particle density inside of a closed system always be the same as the air particle density around the closed system? Bubbles and syringes are closed systems that can expand and shrink — the volumes they enclose are flexible.
Because they can expand and shrink, bubbles and syringes can adjust to the air particle density around them. However, if a container is rigid and cannot expand or shrink, then it cannot adjust to air particle density around it. Let’s see what happens if we put a rigid box filled with air into a vacuum chamber and begin to suck out the air from the vacuum chamber.
As you can see, the air particle density in the rigid box becomes greater than the air particle density in the vacuum chamber around it. This is perfectly okay… as long as the rigid box is well-built and doesn’t end up popping!